Atransferrinemia

Mendelian MONDO:0008846 Pathograph 44 Show in embeddings browser Disorder of iron metabolism and transport Hereditary anemia Inborn error of metal metabolism

Congenital atransferrinemia, also called familial hypotransferrinemia, is a rare autosomal recessive TF-related disorder with markedly reduced circulating transferrin. Reduced transferrin-mediated iron delivery commonly causes microcytic hypochromic anemia in childhood, while disturbed iron sensing and low hepcidin can promote non-transferrin-bound iron accumulation in parenchymal organs. Cardiac, hepatic and endocrine injury can be severe. The spectrum also includes adult-onset iron overload with mild or absent anemia. Residual transferrin, age, treatment and other modifiers complicate genotype-phenotype prediction; neither a universal transferrin threshold nor complete clinical penetrance is established. Management replaces transferrin when needed, controls iron overload according to anemia tolerance, and monitors organ function.

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1
Inheritance
14
Pathophys.
1
Histopath.
27
Phenotypes
3
Gaps
44
Pathograph
1
Genes
4
Variants
8
Medical Actions
1
Trials
2
Models
23
References
1
Deep Research
👪

Inheritance

1
Autosomal recessive HP:0000007
Classic congenital disease is associated with homozygous or compound-heterozygous TF defects. Heterozygous relatives may have reduced transferrin without the severe childhood phenotype. Clinical expression varies substantially even at very low transferrin concentrations; the available kindreds do not establish complete penetrance or exclude modifier effects.
Autosomal recessive inheritance Expressivity: VARIABLE
Show evidence (2 references)
PMID:11110675 SUPPORT PRIMARY RESULT Human Clinical
"Each of the patient's transferrin genes contains one mutation, ie, the patient is a compound heterozygote for these mutations, because one was found in each of her parents."
Segregation of the two parental alleles supports recessive transmission.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
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Discussions and Knowledge Gaps

3
What permits preserved erythropoiesis in some patients with profound transferrin deficiency?
KNOWLEDGE GAP gap_variable_erythropoiesis
Attached to
pathophysiology#Reduced Erythroid Iron Delivery
Adult sisters and a historical family have mild or absent anemia at very low transferrin levels. Residual carrier availability, other inherited factors and alternative uptake routes are plausible but not resolved. The acquired enteropathy case had trace transferrin and transfusion exposure. None of these clinical observations proves a specific compensatory transporter or a universal safe transferrin threshold.
Show evidence (2 references)
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
PMID:36627980 SUPPORT PRIMARY RESULT Human Clinical
"The mildness of the clinical and haematological manifestations raises questions on possible compensatory mechanisms for erythroblastic iron supply, which remain to be investigated."
The acquired-case authors explicitly frame compensation as an unresolved question.
How do transferrin-dependent sensing and erythroid demand combine to regulate human hepcidin?
KNOWLEDGE GAP gap_human_hepcidin_signals
Attached to
pathophysiology#Reduced Transferrin-Dependent Hepcidin Stimulation pathophysiology#Increased Erythropoietic Drive
The mouse perturbations support separable contributions but do not isolate the complete molecular pathway. Human urinary-hepcidin observations are sparse and treatment-linked; embryonic fish anemia does not reproduce the postnatal mammalian suppression pattern. GDF15/TWSG1 transcripts, proposed ERFE signaling and receptor models should not be promoted into proven necessary human intermediates.
Show evidence (3 references)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"These results suggest that hepcidin expression in hpx mice is regulated both by Tf-restricted erythropoiesis and by Tf through a mechanism independent of its role in erythropoiesis."
Interpretation of perturbation experiments in hpx mice.
PMID:17768112 SUPPORT PRIMARY RESULT Human Clinical
"Urinary hepcidin increased from zero at baseline, when hemoglobin and serum transferrin was low, to a maximum of 98 ng/mg creatinine on day 60, and subsequently decreased."
Longitudinal urinary-hepcidin measurements in one plasma-treated child.
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway, failed to impair hepcidin expression."
Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
Does the newly reported intronic TF deletion alter splicing or protein expression?
KNOWLEDGE GAP gap_intronic_variant_function
Attached to
pathophysiology#Biallelic TF Defect
The 2026 review describes a homozygous intronic deletion, a heterozygous mother and absent population observations, but explicitly classifies the allele as VUS. A compatible severe iron-loading phenotype is not a functional splice assay or sufficient evidence to reclassify the allele.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"Targeted exome sequencing in the proband revealed a novel splice site variant, NC_000003.12:g.133778575_133778576del(NM_001063.3:c.2063-11_2063-10del) in intron 16 of TF in the homozygous state. Segregation analysis in the mother confirmed the variant to be present in the heterozygous state...."
The source explicitly labels the intronic variant uncertain. No RNA or expression experiment proves altered splicing.
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Pathophysiology

14
Biallelic TF Defect
Pathogenic TF alleles reduce the availability of functional circulating transferrin through allele-dependent mechanisms. Genotype alone does not establish a universal protein-folding defect.
Downstream
Reduced Circulating Transferrin Recessive TF defects can markedly reduce circulating protein; the precise expression or processing defect varies by allele.
Show evidence (2 references)
PMID:11110675 SUPPORT PRIMARY RESULT Human Clinical
"Hereditary atransferrinemia is a rare but instructive disorder that has previously been reported in only 8 patients in 6 families. It is characterized by microcytic anemia and by iron loading, and can be treated effectively by plasma infusions. We now report the first case known in the United..."
Molecular characterization and familial segregation support two distinct TF alleles; benign polymorphisms described in the same abstract are not causal variants.
PMID:18097132 SUPPORT PRIMARY RESULT Human Clinical
"DNA analysis of the serum transferrin gene in the patient revealed a previously undescribed mutation in exon 4, a G-->A transition at cDNA 410(Cys137Tyr)."
Primary case variant identification.
Reduced Circulating Transferrin
Severely reduced plasma transferrin limits iron-binding capacity and iron delivery, although trace protein and clinical expression vary.
Animal models
Trf hpx/hpx on a BALB/cJ background in the mechanistic study Mouse Mouse partially recapitulates The hpx splice allele reduces the normal circulating carrier.
Downstream
Reduced Erythroid Iron Delivery Lower transferrin availability reduces receptor-mediated erythroid iron supply; this is not absolute cessation of all erythroid iron uptake.
Reduced Transferrin-Dependent Hepcidin Stimulation Loss of circulating transferrin can weaken the iron-sensing input to hepatic hepcidin regulation.
Non-Transferrin-Bound Iron Accumulation Reduced binding capacity limits safe carriage of circulating iron.
Atransferrinemia Reduced circulating transferrin manifests in this laboratory measurement.
Decreased Total Iron-Binding Capacity Reduced circulating transferrin manifests in this laboratory measurement.
Show evidence (2 references)
PMID:11920219 SUPPORT PRIMARY RESULT Human Clinical
"At diagnosis the patient had serum Tf levels equal to about 1% of the normal values."
Biochemical measurement in a single congenital case.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
Reduced Erythroid Iron Delivery
Loss of transferrin-mediated delivery restricts iron available to erythroid precursors in the classic anemic phenotype. Alternative uptake or residual transferrin may sustain erythropoiesis in some patients.
erythroblast CL:0000765 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves erythroblast (CL:0000765). CL:0000765 is a cell type from the Cell Ontology.
Animal models
gavi transferrin-a splice alleles and transferrin-a morphants Zebrafish Zebrafish partially recapitulates Deficient embryos have reduced hemoglobin staining, improved by partial experimental rescue.
Downstream
Reduced Hemoglobin Synthesis Iron is required for heme and hemoglobin synthesis; reduced supply limits production.
Show evidence (2 references)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral tissues (secondary hemochromatosis) [4]."
Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific transport assay.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
Reduced Hemoglobin Synthesis
Iron restriction impairs hemoglobin production, accounting for hypochromic microcytosis in many childhood cases.
Animal models
Trf hpx/hpx on a BALB/cJ background in the mechanistic study Mouse Mouse partially recapitulates Replacement improves hematologic readouts of iron-restricted erythropoiesis.
Downstream
Hypochromic Microcytic Anemia Reduced hemoglobin production produces the classic anemia phenotype, with variable expression across the TF-related spectrum.
Increased Erythropoietic Drive Anemia can increase erythropoietic drive through systemic compensatory signals; this branch is not present in every nonanemic patient.
Pallor The classic iron-restricted anemia can contribute to this finding, without establishing universal occurrence.
Fatigue The classic iron-restricted anemia can contribute to this finding, without establishing universal occurrence.
Growth Delay The classic iron-restricted anemia can contribute to this finding, without establishing universal occurrence.
Tachycardia The classic iron-restricted anemia can contribute to this finding, without establishing universal occurrence.
Heart Murmur The classic iron-restricted anemia can contribute to this finding, without establishing universal occurrence.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral tissues (secondary hemochromatosis) [4]."
Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific transport assay.
Increased Erythropoietic Drive
Anemic transferrin-deficient patients and mice can increase erythroid demand. This does not by itself prove apoptotic ineffective erythropoiesis, and embryonic fish regulate hepcidin differently.
Downstream
Reduced Hepcidin Production Erythropoietic demand can suppress hepcidin in the postnatal mammalian setting; the cited experiments do not identify erythroferrone as the necessary mediator.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"Transfusion of hpx animals with wild-type red blood cells led to increased hepcidin expression, while hepcidin expression in myeloablated hpx mice increased only if Tf was administered postablation."
Mouse perturbations distinguish erythropoietic and transferrin-dependent contributions; they do not identify a single human mediator.
Reduced Transferrin-Dependent Hepcidin Stimulation
Transferrin also supports hepcidin regulation independently of its immediate erythroid-delivery role. Mouse and embryonic fish experiments support this branch; the complete receptor-to-transcription sequence is not established by those experiments.
Animal models
Trf hpx/hpx on a BALB/cJ background in the mechanistic study Mouse Mouse partially recapitulates Transferrin stimulates hepatic hepcidin after myeloablation.
gavi transferrin-a splice alleles and transferrin-a morphants Zebrafish Zebrafish partially recapitulates Transferrin-a and TfR2 perturbations lower basal hepcidin RNA.
Downstream
Reduced Hepcidin Production Reduced transferrin-dependent signaling contributes to lower hepcidin expression.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"These results suggest that hepcidin expression in hpx mice is regulated both by Tf-restricted erythropoiesis and by Tf through a mechanism independent of its role in erythropoiesis."
Interpretation of perturbation experiments in hpx mice.
Reduced Hepcidin Production
Hepcidin can remain low despite systemic iron overload. A human longitudinal plasma-transfusion study measured changing urinary hepcidin; it did not directly quantify hepatic transcription or prove a specific receptor interaction.
Downstream
Reduced Ferroportin Downregulation Less hepcidin permits more ferroportin to remain available for iron export.
Show evidence (2 references)
PMID:17768112 SUPPORT PRIMARY RESULT Human Clinical
"Urinary hepcidin increased from zero at baseline, when hemoglobin and serum transferrin was low, to a maximum of 98 ng/mg creatinine on day 60, and subsequently decreased."
Longitudinal urinary-hepcidin measurements in one plasma-treated child.
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"Hepcidin is suppressed due to increased erythropoietic drive (115), which is consistent with the increased iron absorption in spite of iron overload."
Review synthesis of the classic transferrin-deficient iron-loading phenotype.
Reduced Ferroportin Downregulation
Low hepcidin reduces the signal that normally internalizes and degrades ferroportin. This applies established iron-regulatory physiology to atransferrinemia rather than reporting a patient ferroportin assay.
Downstream
Increased Iron Entry into Plasma Failure to downregulate iron export increases plasma iron flux from enterocytes and recycling cells.
Show evidence (1 reference)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption..."
Established hepcidin-ferroportin physiology, interpreted within the disorder.
Increased Iron Entry into Plasma
Persistent ferroportin-mediated export favors dietary iron absorption and release of recycled iron despite parenchymal overload.
Downstream
Non-Transferrin-Bound Iron Accumulation Increased iron flux can exceed the reduced available transferrin-binding capacity.
Show evidence (2 references)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"Hepcidin is suppressed due to increased erythropoietic drive (115), which is consistent with the increased iron absorption in spite of iron overload."
Review synthesis of the classic transferrin-deficient iron-loading phenotype.
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption..."
Established hepcidin-ferroportin physiology, interpreted within the disorder.
Non-Transferrin-Bound Iron Accumulation
Very low transferrin-binding capacity permits non-transferrin-bound iron to circulate. Calculated transferrin saturation can be high or exceed 100% when transferrin is extremely low; it is not a universal low-saturation disorder.
Downstream
Parenchymal Iron Accumulation Non-transferrin iron uptake promotes tissue loading; specific transporter necessity is not established in the human reports.
Show evidence (2 references)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"They exhibit high saturation of residual transferrin with iron and accumulate NTBI."
Clinical review of congenital disease.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L (N:<0.5)."
Measured iron indices in the nonanemic adult sister.
Parenchymal Iron Accumulation
Nonerythroid organs take up iron despite iron-restricted erythropoiesis. Hepatic and myocardial iron can be measured directly; the responsible uptake routes differ by tissue.
Downstream
Iron-Associated Oxidative Injury The labile iron fraction can promote oxidative injury; MRI total iron does not measure that fraction or its molecular flux.
Elevated Hepatic Iron Tissue iron accumulation is associated with this iron-status measurement; ferritin is also influenced by inflammation and other conditions.
Elevated Serum Ferritin Tissue iron accumulation is associated with this iron-status measurement; ferritin is also influenced by inflammation and other conditions.
Diabetes Mellitus Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve a patient-specific causal sequence.
Hypothyroidism Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve a patient-specific causal sequence.
Hypoparathyroidism Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve a patient-specific causal sequence.
Cardiac Arrhythmia Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve a patient-specific causal sequence.
Show evidence (2 references)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and iron overload in parenchymal cells of the liver, heart and pancreas."
Clinical review describes the classic phenotype; later familial observations establish that severe childhood anemia is not universal.
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"T2* quantification estimated a cardiac iron concentration of 5.3 mg/g (normal <1 mg/g) and hepatic iron concentration of 17.8 mg/g (normal 0.8-1.16 mg/g), confirming severe iron overload."
MRI iron quantification in the clinically affected child; its TF allele remains a VUS.
Iron-Associated Oxidative Injury
Redox-active iron can generate reactive species and damage membranes, proteins and nucleic acids. The cited review draws this mechanism from broader iron-overload cardiomyopathy; it was not directly measured in the atransferrinemic child.
Downstream
Myocardial Dysfunction Oxidative injury and altered calcium handling may contribute to dysfunction; human case evidence does not isolate this sequence.
Hepatic Fibrotic Injury Chronic iron-related injury can provoke hepatic fibrogenic repair, although this sequence was not experimentally tested in the reported patients.
Show evidence (1 reference)
PMID:41220266 SUPPORT BACKGROUND Human Clinical
"These radicals cause lipid peroxidation, nucleic acid damage, and protein dysfunction, disrupting cellular antioxidant defenses."
General iron-overload mechanism summarized in the clinical review, not an assay of the reported patient.
Myocardial Dysfunction
Iron-associated injury can impair myocardial function. The relative roles of iron toxicity and anemia-related circulatory demand vary and are not isolated by the case reports.
Downstream
Cardiomyopathy Impaired myocardial function can manifest clinically in this form.
Heart Failure Impaired myocardial function can manifest clinically in this form.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia, and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,..."
Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
Hepatic Fibrotic Injury
Chronic hepatic iron injury can be accompanied by fibrosis and cirrhosis; not every patient with MRI iron has established fibrosis.
Downstream
Hepatic Fibrosis Hepatic fibrotic injury can produce this clinical or pathological finding.
Cirrhosis Hepatic fibrotic injury can produce this clinical or pathological finding.
Show evidence (2 references)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"CT workup revealed cirrhosis with ascites."
Cirrhosis was observed in the adult index case with later documented severe iron overload.
✶

Histopathology

1
Myocardial iron deposition and fibrosis
The explanted heart of the adult index patient showed widespread cardiomyocyte iron and fibrosis. The patient died of primary graft failure; this does not establish that all iron cardiomyopathy is irreversible or that graft iron deposition caused death.
Show evidence (1 reference)
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Pathological examination of the explant ed heart revealed widespread iron overload and fibrosis in the cardiomyocytes."
Primary pathological finding in one adult with homozygous TF p.Glu370Lys.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Atransferrinemia Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

27
Blood 1
Hypochromic Microcytic Anemia HP:0004840 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypochromic microcytic anemia (HP:0004840). HP:0004840 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:19579082 SUPPORT PRIMARY RESULT Human Clinical
"Further evaluations indicate severe hypochromic microcytic anemia with decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient. The serum level of transferrin was decreased."
Directly documents the severe hypochromic microcytic anemia with the characteristic low iron/TIBC and high ferritin laboratory pattern.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
Cardiovascular 6
Cardiomyopathy HP:0001638 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cardiomyopathy (HP:0001638). HP:0001638 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia, and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,..."
Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
Splenomegaly HP:0001744 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Splenomegaly (HP:0001744). HP:0001744 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"Examination revealed pallor and mild hepatosplenomegaly."
Observed in the four-year-old girl, who had no molecular testing or subsequent treatment follow-up.
Heart Failure Congestive heart failure HP:0001635 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Congestive heart failure (HP:0001635). HP:0001635 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia, and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,..."
Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
Cardiac Arrhythmia HP:0011675 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Arrhythmia (HP:0011675). HP:0011675 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
Tachycardia HP:0001649 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tachycardia (HP:0001649). HP:0001649 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Heart Murmur HP:0030148 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Heart murmur (HP:0030148). HP:0030148 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Digestive 5
Elevated Hepatic Iron Elevated hepatic iron concentration HP:0012465 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Elevated hepatic iron concentration (HP:0012465). HP:0012465 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"T2* quantification estimated a cardiac iron concentration of 5.3 mg/g (normal <1 mg/g) and hepatic iron concentration of 17.8 mg/g (normal 0.8-1.16 mg/g), confirming severe iron overload."
MRI iron quantification in the clinically affected child; its TF allele remains a VUS.
Hepatomegaly HP:0002240 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hepatomegaly (HP:0002240). HP:0002240 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"Examination revealed pallor and mild hepatosplenomegaly."
Observed in the four-year-old girl, who had no molecular testing or subsequent treatment follow-up.
Hepatic Fibrosis HP:0001395 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hepatic fibrosis (HP:0001395). HP:0001395 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
Cirrhosis HP:0001394 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cirrhosis (HP:0001394). HP:0001394 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"CT workup revealed cirrhosis with ascites."
Cirrhosis was observed in the adult index case with later documented severe iron overload.
Poor Appetite HP:0004396 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Poor appetite (HP:0004396). HP:0004396 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"A 4-year-old girl, born of non consanguineous marriage was apparently well till 10 months of age, when her parents noticed pallor and lethargy with poor oral intake."
Primary case observation.
Endocrine 3
Diabetes Mellitus HP:0000819 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Diabetes mellitus (HP:0000819). HP:0000819 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia, and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,..."
Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
Hypothyroidism HP:0000821 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypothyroidism (HP:0000821). HP:0000821 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
Hypoparathyroidism HP:0000829 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoparathyroidism (HP:0000829). HP:0000829 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism."
Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory organ sequence is established.
Genitourinary 1
Hypospadias HP:0000047 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypospadias (HP:0000047). HP:0000047 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"Examination revealed pallor and coronal hypospadias (asymptomatic)."
Direct observation in one clinically diagnosed boy.
Immune 1
Recurrent Infections HP:0002719 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent infections (HP:0002719). HP:0002719 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Integument 1
Pallor HP:0000980 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pallor (HP:0000980). HP:0000980 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Metabolism 4
Atransferrinemia HP:0012239 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Atransferrinemia (HP:0012239). HP:0012239 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11920219 SUPPORT PRIMARY RESULT Human Clinical
"At diagnosis the patient had serum Tf levels equal to about 1% of the normal values."
Severe measured transferrin deficiency in a congenital case.
Decreased Serum Iron Decreased circulating iron concentration HP:0040303 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased circulating iron concentration (HP:0040303). HP:0040303 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19579082 SUPPORT PRIMARY RESULT Human Clinical
"decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient"
Documents the low serum iron of the characteristic iron-study pattern.
Decreased Total Iron-Binding Capacity HP:0033211 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased total iron binding capacity (HP:0033211). HP:0033211 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19579082 SUPPORT PRIMARY RESULT Human Clinical
"decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient"
Documents the reduced TIBC that, with low serum iron and high ferritin, forms the disorder's biochemical signature.
Elevated Serum Ferritin Increased circulating ferritin concentration HP:0003281 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Increased circulating ferritin concentration (HP:0003281). HP:0003281 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19579082 SUPPORT PRIMARY RESULT Human Clinical
"decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient"
Documents the elevated serum ferritin reflecting body iron overload despite the concurrent anemia.
Musculoskeletal 1
Osteoporosis HP:0000939 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Osteoporosis (HP:0000939). HP:0000939 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Human Clinical
"skin iron deposition, and sometimes fatal cardiomyopathy. Some patients have osteoporosis."
The guideline identifies this complication; its exact prevalence and mediation are not established.
Nervous System 1
Neurodevelopmental Delay HP:0012758 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neurodevelopmental delay (HP:0012758). HP:0012758 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Human Clinical
"Affected children may show a failure to thrive with occasional retardation in mental development."
Clinical synthesis in the 2014 guideline; developmental assessment methods and a phenotype denominator are not supplied.
Constitutional 1
Fatigue HP:0012378 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fatigue (HP:0012378). HP:0012378 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Growth 2
Growth Delay HP:0001510 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Growth delay (HP:0001510). HP:0001510 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:28824244 SUPPORT BACKGROUND Human Clinical
"Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections."
Background clinical spectrum; these manifestations were not all observed in the two reported children.
Failure to Thrive HP:0001508 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Failure to thrive (HP:0001508). HP:0001508 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Human Clinical
"Affected children may show a failure to thrive with occasional retardation in mental development."
Clinical synthesis in the 2014 guideline; developmental assessment methods and a phenotype denominator are not supplied.
🧬

Genetic Associations

1
TF
Gene: TF hgnc:11740 gene page HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TF (hgnc:11740). hgnc:11740 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (5 references)
PMID:11110675 SUPPORT PRIMARY RESULT Human Clinical
"Hereditary atransferrinemia is a rare but instructive disorder that has previously been reported in only 8 patients in 6 families. It is characterized by microcytic anemia and by iron loading, and can be treated effectively by plasma infusions. We now report the first case known in the United..."
Molecular characterization and familial segregation support two distinct TF alleles; benign polymorphisms described in the same abstract are not causal variants.
PMID:18097132 SUPPORT PRIMARY RESULT Human Clinical
"DNA analysis of the serum transferrin gene in the patient revealed a previously undescribed mutation in exon 4, a G-->A transition at cDNA 410(Cys137Tyr)."
Primary case variant identification.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Genetic analysis revealed homozygous TF variant NM_001063.3:c.1108G>A , p.(Glu370Lys). No other variants were found in the gene panel."
Targeted panel result from one family; does not exclude every modifier outside the tested panel.
+ 2 more references
Variants (4)
TF p.Ala477Pro with a second deletion-insertion allele
The first molecularly characterized US case had two different alleles: p.Ala477Pro and a 10-bp deletion with 9-bp insertion. Segregation and conservation supported causality; the accessible abstract does not report a secretion assay.
TF p.Cys137Tyr
Exon-4 c.410G>A was reported in the Turkish case subsequently followed under plasma plus iron treatment; these publications concern one patient.
TF p.Glu370Lys
Homozygous c.1108G>A in two adult sisters with severe hypotransferrinemia and iron overload; classified as likely pathogenic by the 2025 authors using prediction and segregation, without a reported functional assay.
TF c.2063-11_2063-10del
A homozygous intronic variant in a 13-year-old with anemia, cardiac/hepatic iron and diabetes. The source explicitly classifies it as a variant of uncertain significance; rarity and segregation do not establish a splice defect.
💊

Medical Actions

8
Plasma transferrin replacement
Action: Fresh Frozen Plasma TransfusionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Fresh Frozen Plasma Transfusion (NCIT:C116475). NCIT:C116475 is a clinical intervention from the NCI Thesaurus. NCIT:C116475
Platform: Other
Plasma infusions supply transferrin and can improve iron-restricted erythropoiesis. Dose and interval are individualized to hemoglobin, transferrin and clinical course; a fixed monthly schedule may become insufficient during growth. Case reports do not establish uniform tissue-iron clearance or comparative product efficacy.
Mechanism Target:
RESTORES Reduced Circulating Transferrin — Exogenous plasma supplies the deficient circulating carrier.
Show evidence (1 reference)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine, hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig ervaring)."
The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting limited apotransferrin experience. Its evidence base consists of small case reports.
RESTORES Reduced Erythroid Iron Delivery — Replacement supports erythroid iron delivery and hemoglobin production.
Show evidence (1 reference)
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"The patient has responded to treatment regimen of monthly infusions of fresh frozen plasma (FFP), with an increase of reticulocyte count to 6% at 2 weeks, Hb rise to 12.4 mg/dL at 1 month and decline of serum ferritin to 903 µg/L after 12 months."
Response was documented in the boy only; the girl was lost to follow-up. The quoted hemoglobin unit is the source’s typographical error and is not used as a dose or treatment target.
Show evidence (4 references)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine, hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig ervaring)."
The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting limited apotransferrin experience. Its evidence base consists of small case reports.
PMID:28824244 SUPPORT PRIMARY RESULT Human Clinical
"The patient has responded to treatment regimen of monthly infusions of fresh frozen plasma (FFP), with an increase of reticulocyte count to 6% at 2 weeks, Hb rise to 12.4 mg/dL at 1 month and decline of serum ferritin to 903 µg/L after 12 months."
Response was documented in the boy only; the girl was lost to follow-up. The quoted hemoglobin unit is the source’s typographical error and is not used as a dose or treatment target.
PMID:17768112 SUPPORT PRIMARY RESULT Human Clinical
"Hemoglobin pr ogressively increased reaching normal values during the third month."
Response to intensified plasma replacement in one child; plasma volume and frequency changed together.
+ 1 more reference
Purified apotransferrin replacement
Action: Therapeutic ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Therapeutic Procedure (NCIT:C49236). NCIT:C49236 is a clinical intervention from the NCI Thesaurus. NCIT:C49236
Platform: Protein replacement
Purified transferrin or apotransferrin is an alternative replacement approach described in small historical reports. Availability, optimal dosing and comparative long-term outcomes remain limited. Normalization of hemoglobin does not guarantee removal of accumulated organ iron.
Mechanism Target:
RESTORES Reduced Circulating Transferrin — Replacement provides functional iron-binding protein.
Show evidence (1 reference)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine, hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig ervaring)."
The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting limited apotransferrin experience. Its evidence base consists of small case reports.
Show evidence (4 references)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine, hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig ervaring)."
The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting limited apotransferrin experience. Its evidence base consists of small case reports.
PMID:8317485 SUPPORT PRIMARY RESULT Human Clinical
"The long-term clinical, laboratory, and developmental observations revealed that after 5 years of apo-TF supplementary therapy the patient's anemia gradually disappeared, and he started to grow again without further therapy."
Historical family-specific longitudinal observation; residual transferrin increased, so lasting benefit cannot be assigned solely to a short-term pharmacological effect.
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Other
"Transferrin supplementation by either plasma transfusion or apotransferrin infusion is recommended in patients with hypotransferrinemia due to a TF defect."
Disease-specific recommendation from Donker et al. 2014 (PMID:24665134), whose evidence base is mainly case reports and small series.
+ 1 more reference
Iron chelation
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: desferrioxamine B CHEBI:4356 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses desferrioxamine B (CHEBI:4356). CHEBI:4356 is a therapeutic agent from Chemical Entities of Biological Interest. deferiprone CHEBI:68554 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses deferiprone (CHEBI:68554). CHEBI:68554 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Chelation is considered for documented iron overload according to organ burden and clinical status. Desferrioxamine followed by deferiprone was used in the recent pediatric report, but its planned follow-up MRI result is not supplied. Drug selection, toxicity surveillance and efficacy estimates cannot be inferred from that single exposure.
Mechanism Target:
INHIBITS Parenchymal Iron Accumulation — Chelation aims to lower body and organ iron burden; the cited pediatric case documents use, not a measured response.
Show evidence (2 references)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine en klachten. Als alternatief kan chelatie therapie worden gegeven."
The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation as an alternative; it does not endorse routine blood removal despite severe anemia.
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"The patient was initiated on iron chelation therapy with injectable desferrioxamine, followed by oral deferiprone. A repeat MRI was planned after six months to evaluate treatment efficacy and guide further management."
Observed treatment exposure without reported follow-up efficacy in this case.
Show evidence (3 references)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine en klachten. Als alternatief kan chelatie therapie worden gegeven."
The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation as an alternative; it does not endorse routine blood removal despite severe anemia.
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"The patient was initiated on iron chelation therapy with injectable desferrioxamine, followed by oral deferiprone. A repeat MRI was planned after six months to evaluate treatment efficacy and guide further management."
Observed treatment exposure without reported follow-up efficacy in this case.
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Other
"In case of systemic iron loading, phlebotomies are recommended. If phlebotomies are not tolerated because of decreasing Hb, chelation therapy is rec ommended."
The published guideline explicitly makes chelation an alternative when falling hemoglobin limits phlebotomy; the word break is preserved from the generated PDF.
Therapeutic phlebotomy in selected patients
Action: PhlebotomyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Phlebotomy (NCIT:C28221). NCIT:C28221 is a clinical intervention from the NCI Thesaurus. NCIT:C28221
Platform: Other
Blood removal can lower iron burden when erythropoiesis and hemoglobin permit. The guideline advises adjustment to hemoglobin, ferritin and symptoms. One nonanemic adult sister tolerated monthly phlebotomy without transferrin replacement; this must not be generalized to severely anemic children.
Mechanism Target:
INHIBITS Parenchymal Iron Accumulation — Blood removal lowers stored iron; the cited adult response was measured by ferritin, without a paired follow-up tissue-iron result.
Show evidence (1 reference)
PMID:40112917 SUPPORT INDIRECT PRIMARY RESULT Human Clinical
"Bloodletting (300cc month ly w ithout plasma or purified transferrin supplementation) was well tolerated and efficient ; after one year of treatment, the ferritin level was 115µg/L without anemia."
Observed outcome in the nonanemic adult sister, not evidence of tolerability in patients with profound anemia.
Show evidence (3 references)
url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html SUPPORT REVIEW SYNTHESIS Other
"In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine en klachten. Als alternatief kan chelatie therapie worden gegeven."
The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation as an alternative; it does not endorse routine blood removal despite severe anemia.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Bloodletting (300cc month ly w ithout plasma or purified transferrin supplementation) was well tolerated and efficient ; after one year of treatment, the ferritin level was 115µg/L without anemia."
Observed outcome in the nonanemic adult sister, not evidence of tolerability in patients with profound anemia.
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Other
"In case of systemic iron loading, phlebotomies are recommended. If phlebotomies are not tolerated because of decreasing Hb, chelation therapy is rec ommended."
The published guideline explicitly makes chelation an alternative when falling hemoglobin limits phlebotomy; the word break is preserved from the generated PDF.
Individualized iron supplementation with transferrin replacement
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Platform: Small molecule
Iron alone does not correct carrier deficiency and can aggravate loading. A Turkish patient received oral iron with regular plasma and later an individualized change in duration to maintain hemoglobin. This uncontrolled, overlapping follow-up does not support routine supplementation in iron-overloaded patients or establish superiority over adequate transferrin replacement.
Mechanism Target:
MODULATES Reduced Erythroid Iron Delivery — Iron supplied alongside replacement may alter marrow availability in an individually monitored patient; its independent effect is unresolved.
Show evidence (1 reference)
PMID:34792309 SUPPORT PRIMARY RESULT Human Clinical
"In conclusion, our experience of almost 14 years reveals that fresh frozen plasma plus iron therapy may be advantageous over standard fresh frozen plasma transfusion. With this therapy, the stable Hb control seen in this case in the first decade was re-achieved in the second decade."
Single-patient experience without a randomized comparator; proposed superiority is not established.
Show evidence (2 references)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"Blood transfusions or treatments with iron are ineffective and aggravate iron overload."
General caution about treatment that does not correct transferrin deficiency; paired iron-plus-replacement is considered separately.
PMID:34792309 SUPPORT PRIMARY RESULT Human Clinical
"In conclusion, our experience of almost 14 years reveals that fresh frozen plasma plus iron therapy may be advantageous over standard fresh frozen plasma transfusion. With this therapy, the stable Hb control seen in this case in the first decade was re-achieved in the second decade."
Single-patient experience without a randomized comparator; proposed superiority is not established.
Cardiac and endocrine complication management
Action: Therapeutic ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Therapeutic Procedure (NCIT:C49236). NCIT:C49236 is a clinical intervention from the NCI Thesaurus. NCIT:C49236
Platform: Other
Cardiac failure and diabetes require specialist management alongside iron-directed treatment. The review discusses conventional heart-failure therapy but explicitly lacks atransferrinemia-specific evidence for newer adult HFrEF agents; their adult efficacy is not a pediatric disease-specific recommendation.
Show evidence (2 references)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia, and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,..."
Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
PMID:41220266 SUPPORT BACKGROUND Human Clinical
"Although ARNIs and SGLT2 inhibitors have not been specifically studied in iron overload cardiomyopathies or atransferrinemia, they have shown efficacy in heart failure with reduced ejection fraction (HFrEF) in adults. The treatment should be tailored according to the clinical presentation of the..."
The review explicitly distinguishes adult HFrEF evidence from disease-specific evidence.
Longitudinal iron and organ surveillance
Action: Therapeutic ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Therapeutic Procedure (NCIT:C49236). NCIT:C49236 is a clinical intervention from the NCI Thesaurus. NCIT:C49236
Platform: Other
Follow hemoglobin, transferrin, ferritin and symptoms, with tissue-iron imaging and organ assessment where indicated. Serum ferritin alone does not identify the distribution of cardiac versus hepatic iron. Growth and treatment requirements may change over time.
Show evidence (3 references)
PMID:28824244 SUPPORT REVIEW SYNTHESIS Other
"Our patients need to be in long-term follow-up to monitor the effectiveness of therapy and manage iron overload."
Authors recommend ongoing monitoring; only one of their two patients remained in follow-up.
PMID:41220266 SUPPORT BACKGROUND Human Clinical
"Cardiac MRI T2* remains a unique and reliable modality for diagnosing and quantifying cardiac iron overload and monitoring therapy in iron overload cardiomyopathies, including atransferrinemia."
Review supports the imaging role, without a controlled mortality benefit.
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf SUPPORT REVIEW SYNTHESIS Other
"Iron status should be monitored in patients with hypotransferrinemia due to a TF defect in order to detect toxic iron loading early."
Published disease-specific monitoring recommendation, not an outcome comparison.
Genetic counseling and family evaluation
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Platform: Other
Explain recessive inheritance, variant uncertainty and the variable anemia/iron-overload phenotype. Offer targeted familial testing and iron studies when a relevant variant is established; do not treat every rare variant as pathogenic.
Show evidence (2 references)
PMID:28824244 SUPPORT REVIEW SYNTHESIS Other
"Diagnosis is confirmed by molecular genetic testing for mutation in the TF gene. Genetic counseling is available."
Clinical diagnostic and counseling recommendation.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Family screening revealed her sister (52yo) was homozygous for the same TF variant."
Family investigation identified a nonanemic relative with significant iron overload.
🔬

Biochemical Markers

3
Urinary hepcidin response during plasma replacement
Show evidence (1 reference)
PMID:17768112 SUPPORT PRIMARY RESULT Human Clinical
"Urinary hepcidin increased from zero at baseline, when hemoglobin and serum transferrin was low, to a maximum of 98 ng/mg creatinine on day 60, and subsequently decreased."
Longitudinal urinary-hepcidin measurements in one plasma-treated child.
Non-transferrin-bound iron
Show evidence (1 reference)
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L (N:<0.5)."
Measured iron indices in the nonanemic adult sister.
Abnormal circulating transferrin molecular forms
Show evidence (1 reference)
PMID:11920219 SUPPORT PRIMARY RESULT Human Clinical
"Protein analyses indicate that the proband serum contains two transferrin forms: one of 80 kD analogous to the normal one, and a smaller one of 50 kD, which may arise from a specific degradation or be the gene product of a modified allele."
Observed serum protein forms with explicitly unresolved origin of the smaller species.
🔬

Diagnosis

4
Integrated iron and hematologic assessment
Measure transferrin directly alongside hemoglobin, indices, serum iron, TIBC and ferritin. Severe childhood iron-refractory microcytosis is a classic trigger, but unexplained parenchymal iron overload with very low transferrin also warrants evaluation in adults without anemia. Calculated transferrin saturation is variable and can exceed 100% with a very small denominator; no fixed low-saturation threshold is diagnostic.
Laboratory Procedure NCIT:C25294 NCI Thesaurus (NCIT)
Show evidence (3 references)
PMID:19579082 SUPPORT PRIMARY RESULT Human Clinical
"Further evaluations indicate severe hypochromic microcytic anemia with decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient. The serum level of transferrin was decreased."
Directly documents the severe hypochromic microcytic anemia with the characteristic low iron/TIBC and high ferritin laboratory pattern.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L (N:<0.5)."
Measured iron indices in the nonanemic adult sister.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
TF molecular testing and variant interpretation
Sequence TF and evaluate segregation and variant class in the clinical context. A VUS does not by itself establish the molecular diagnosis or a splice defect; RNA or other appropriate functional analysis may be needed. Clinical reports without testing remain clinically diagnosed.
Genetic Testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:28824244 SUPPORT REVIEW SYNTHESIS Other
"Diagnosis is confirmed by molecular genetic testing for mutation in the TF gene."
Clinical recommendation.
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"Targeted exome sequencing in the proband revealed a novel splice site variant, NC_000003.12:g.133778575_133778576del(NM_001063.3:c.2063-11_2063-10del) in intron 16 of TF in the homozygous state. Segregation analysis in the mother confirmed the variant to be present in the heterozygous state...."
The source explicitly labels the intronic variant uncertain. No RNA or expression experiment proves altered splicing.
Cardiac and hepatic iron assessment
MRI-based tissue-iron assessment and cardiac functional imaging characterize burden and complications. Hepatic and myocardial iron may differ within one patient; iron quantification is not a direct assay of oxidative injury or proof of fibrosis.
Magnetic Resonance Imaging NCIT:C16809 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:41220266 SUPPORT PRIMARY RESULT Human Clinical
"T2* quantification estimated a cardiac iron concentration of 5.3 mg/g (normal <1 mg/g) and hepatic iron concentration of 17.8 mg/g (normal 0.8-1.16 mg/g), confirming severe iron overload."
MRI iron quantification in the clinically affected child; its TF allele remains a VUS.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Cardiac MRI findings were normal, without iron overload."
The adult sister had liver iron overload but normal cardiac MRI, showing tissue-specific heterogeneity.
Exclude acquired hypotransferrinemia
Assess liver disease, inflammation, nutritional status and protein losses. A reversible adult acquired case recovered transferrin after treatment of enteropathy; age alone cannot exclude congenital disease because late-presenting homozygous TF cases are now documented.
Show evidence (2 references)
PMID:36627980 SUPPORT PRIMARY RESULT Human Clinical
"The most convincing argument was the subsequent normalization of serum Tf after the resolution of the acute episode."
Recovery supported an acquired explanation in that patient; its other exclusion arguments should not be universalized.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
📈

Progression

2
Variable childhood or adult presentation
Severe iron-refractory anemia and growth impairment commonly prompt childhood diagnosis. Adult-onset iron loading with mild or absent anemia is documented; therefore anemia onset, organ-failure sequence and untreated mortality cannot be assigned universal ages or frequencies.
Show evidence (2 references)
PMID:30420953 SUPPORT REVIEW SYNTHESIS Human Clinical
"This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and iron overload in parenchymal cells of the liver, heart and pancreas."
Clinical review describes the classic phenotype; later familial observations establish that severe childhood anemia is not universal.
PMID:40112917 SUPPORT PRIMARY RESULT Human Clinical
"Interestingly, although serum transferrin was similar to previously described cases, anemia was mild in the index patient, and was absent in her sister."
Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance estimate.
Treatment and organ burden over time
Replacement can improve hemoglobin, but dose or interval may need reassessment with growth. Ferritin, transferrin and tissue iron are distinct measurements, and established organ injury may persist. Long-term clinical series are small and often repeat the same patients.
Show evidence (1 reference)
PMID:34792309 SUPPORT PRIMARY RESULT Human Clinical
"However, at the start of the second decade, Hb and ferritin began to decline and the therapy was revised."
Within-patient longitudinal change after the first decade of treatment; not proof of treatment failure in every patient.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
The 2018 follow-up cited only 16 published cases at that time. Later families and overlapping follow-up reports preclude treating that historical count as a current total or deriving population prevalence.
Show evidence (1 reference)
PMID:28895280 SUPPORT BACKGROUND Human Clinical
"Since its description in 1961, only 16 cases have been reported."
Historical literature count in a case follow-up, not a population denominator or current cumulative count.
🔬

Clinical Trials

1
NCT01797055 PHASE_II ACTIVE_NOT_RECRUITING
This phase II open-label, single-group study evaluates intravenous human apotransferrin replacement. The official record updated September 16, 2026 lists five actual participants, active-not-recruiting status and estimated completion in January 2028. Outcomes include hemoglobin, transferrin pharmacokinetics, organ iron and adverse reactions. No results are posted; the registry does not establish clinical benefit or the optimal regimen. Its transferrin below 40 mg/dL eligibility threshold is a study criterion, not a universal diagnostic cutoff.
Target Phenotypes: Hypochromic microcytic anemia HP:0004840 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Hypochromic microcytic anemia (HP:0004840). HP:0004840 is a phenotype from the Human Phenotype Ontology. Atransferrinemia HP:0012239 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Atransferrinemia (HP:0012239). HP:0012239 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
clinicaltrials:NCT01797055 SUPPORT BACKGROUND Other
"The objective of this study is to investigate the pharmacokinetics, efficacy and safety of Apotransferrin replacement therapy in atransferrinemia patients."
Registry study objective, not a reported efficacy or safety result.
url:https://clinicaltrials.gov/api/v2/studies/NCT01797055 SUPPORT BACKGROUND Other
"serum transferrin levels measured on several time points before and after infusion"
Prespecified pharmacokinetic outcome in the complete official registry record, not a posted result.
🐁

Animal Models

2
Trf hpx/hpx on a BALB/cJ background in the mechanistic study Mouse
The spontaneous splice-donor allele produces severe transferrin deficiency, anemia and nonhematopoietic iron loading. The 2011 study compared replacement, washed wild-type red-cell transfusion and myeloablation followed by transferrin. Replacement improved hematologic and hepcidin readouts; withdrawal allowed recurrence. Suppression of erythropoiesis and restoration of transferrin make separable contributions. The study does not establish apoptosis of immature erythrocytes, a complete human signaling chain or universal clinical rescue.
Species
Mouse
Genotype
Trf hpx/hpx on a BALB/cJ background in the mechanistic study
Genes
TF hgnc:11740 HUGO Gene Nomenclature Committee (hgnc) Relation: this experimental model concerns this gene This experimental model concerns TF (hgnc:11740). hgnc:11740 is a gene from the HUGO Gene Nomenclature Committee.
Pathograph links
Reduced Circulating Transferrin partially recapitulates fidelity: moderate observes: molecular The hpx splice allele reduces the normal circulating carrier.
Limitations: This postnatal mouse splice defect models severe deficiency, not every human missense allele or the nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation. No specific human receptor or erythroid mediator is isolated.
Readouts
Abnormal Trf splicing
Direction: ALTERED
Interpretation: The hpx splice allele reduces the normal circulating carrier.
Show evidence (1 reference)
PMID:10910930 SUPPORT PRIMARY RESULT Model Organism
"It results from a single point mutation, which alters an invariable nucleotide in the splice donor site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from the hpx allele."
Defined spontaneous mouse splice defect; the accessible source is an abstract.
Show evidence (1 reference)
PMID:10910930 SUPPORT PRIMARY RESULT Model Organism
"It results from a single point mutation, which alters an invariable nucleotide in the splice donor site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from the hpx allele."
Defined spontaneous mouse splice defect; the accessible source is an abstract.
Reduced Hemoglobin Synthesis partially recapitulates fidelity: moderate observes: cellular Replacement improves hematologic readouts of iron-restricted erythropoiesis.
Limitations: This postnatal mouse splice defect models severe deficiency, not every human missense allele or the nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation. No specific human receptor or erythroid mediator is isolated.
Readouts
Hematocrit response
Direction: ALTERED
Interpretation: Replacement improves hematologic readouts of iron-restricted erythropoiesis.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"By the third day of treatment, spleen masses had decreased and hematocrits had normalized; by the sixth day of treatment, hepcidin levels were elevated from baseline to levels similar to those observed in wild-type mice (data not shown). Six weeks after cessation of treatment, hematocrits,..."
Main-body report of rapid response and recurrence after withdrawal; the numerical data are not shown in the paper.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"By the third day of treatment, spleen masses had decreased and hematocrits had normalized; by the sixth day of treatment, hepcidin levels were elevated from baseline to levels similar to those observed in wild-type mice (data not shown). Six weeks after cessation of treatment, hematocrits,..."
Main-body report of rapid response and recurrence after withdrawal; the numerical data are not shown in the paper.
Reduced Transferrin-Dependent Hepcidin Stimulation partially recapitulates fidelity: moderate observes: molecular Transferrin stimulates hepatic hepcidin after myeloablation.
Limitations: This postnatal mouse splice defect models severe deficiency, not every human missense allele or the nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation. No specific human receptor or erythroid mediator is isolated.
Readouts
Hepatic hepcidin RNA after transferrin
Direction: ALTERED
Interpretation: Transferrin stimulates hepatic hepcidin after myeloablation.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by approximately eighty-fold and seventeen-fold, respectively (Figure 6F)."
Transferrin stimulation after myeloablation supports an erythropoiesis-independent component. Different protein doses prevent a human-versus-mouse potency comparison.
Show evidence (1 reference)
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by approximately eighty-fold and seventeen-fold, respectively (Figure 6F)."
Transferrin stimulation after myeloablation supports an erythropoiesis-independent component. Different protein doses prevent a human-versus-mouse potency comparison.
Show evidence (3 references)
PMID:10910930 SUPPORT PRIMARY RESULT Model Organism
"It results from a single point mutation, which alters an invariable nucleotide in the splice donor site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from the hpx allele."
Defined spontaneous mouse splice defect; the accessible source is an abstract.
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"By the third day of treatment, spleen masses had decreased and hematocrits had normalized; by the sixth day of treatment, hepcidin levels were elevated from baseline to levels similar to those observed in wild-type mice (data not shown). Six weeks after cessation of treatment, hematocrits,..."
Main-body report of rapid response and recurrence after withdrawal; the numerical data are not shown in the paper.
PMID:20956801 SUPPORT PRIMARY RESULT Model Organism
"Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by approximately eighty-fold and seventeen-fold, respectively (Figure 6F)."
Transferrin stimulation after myeloablation supports an erythropoiesis-independent component. Different protein doses prevent a human-versus-mouse potency comparison.
gavi transferrin-a splice alleles and transferrin-a morphants Zebrafish
Two recessive gavi splice alleles predict truncated transferrin-a and produce hypochromic anemia with early lethality. Morpholino knockdown reproduced reduced hemoglobin and tissue-iron staining; transferrin-a cRNA partially restored them. TfR2 knockdown reduced hepcidin without anemia, whereas anemia induced outside the transferrin pathway did not lower basal embryonic hepcidin. The complete main body, methods and captions were reviewed; separate supplementary objects were not assessed.
Species
Zebrafish
Genotype
gavi transferrin-a splice alleles and transferrin-a morphants
Genes
TF hgnc:11740 HUGO Gene Nomenclature Committee (hgnc) Relation: this experimental model concerns this gene This experimental model concerns TF (hgnc:11740). hgnc:11740 is a gene from the HUGO Gene Nomenclature Committee.
Pathograph links
Reduced Erythroid Iron Delivery partially recapitulates fidelity: moderate observes: cellular Deficient embryos have reduced hemoglobin staining, improved by partial experimental rescue.
Limitations: Nonfeeding embryos were examined mainly at 48–72 hours after fertilization; reduced somite/proctodeal iron is not adult parenchymal overload. Histochemistry and hepcidin RNA do not directly measure transport flux or protein secretion. Rescue is partial and experimental, not a human treatment comparison. Human HFE circuitry is not established in this fish system.
Readouts
Hemoglobin histochemistry
Direction: DECREASED
Interpretation: Deficient embryos have reduced hemoglobin staining, improved by partial experimental rescue.
Show evidence (1 reference)
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype and decreased somite and terminal gut iron staining, while coinjection of transferrin-a cRNA partially restored these defects."
Embryonic perturbation and partial rescue of histochemical readouts.
Show evidence (1 reference)
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype and decreased somite and terminal gut iron staining, while coinjection of transferrin-a cRNA partially restored these defects."
Embryonic perturbation and partial rescue of histochemical readouts.
Reduced Transferrin-Dependent Hepcidin Stimulation partially recapitulates fidelity: moderate observes: molecular Transferrin-a and TfR2 perturbations lower basal hepcidin RNA.
Limitations: Nonfeeding embryos were examined mainly at 48–72 hours after fertilization; reduced somite/proctodeal iron is not adult parenchymal overload. Histochemistry and hepcidin RNA do not directly measure transport flux or protein secretion. Rescue is partial and experimental, not a human treatment comparison. Human HFE circuitry is not established in this fish system.
Readouts
Embryonic hepcidin expression
Direction: DECREASED
Interpretation: Transferrin-a and TfR2 perturbations lower basal hepcidin RNA.
Show evidence (1 reference)
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway, failed to impair hepcidin expression."
Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
Show evidence (1 reference)
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway, failed to impair hepcidin expression."
Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
Show evidence (3 references)
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype and decreased somite and terminal gut iron staining, while coinjection of transferrin-a cRNA partially restored these defects."
Embryonic perturbation and partial rescue of histochemical readouts.
PMID:19047682 SUPPORT PRIMARY RESULT Model Organism
"Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway, failed to impair hepcidin expression."
Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2661867/ SUPPORT PRIMARY RESULT Model Organism
"both of which exhibit a recessive pattern of inheritance, hypochromic anemia at 48 hpf"
The complete primary Results section describes both gavi alleles; embryonic phenotype timing is not a human onset estimate.
{ }

Source YAML

click to show 
name: Atransferrinemia
creation_date: '2026-08-08T00:00:00Z'
category: Mendelian
disease_term:
  preferred_term: congenital atransferrinemia
  term:
    id: MONDO:0008846
    label: atransferrinemia
parents:
- Disorder of iron metabolism and transport
- Hereditary anemia
- Inborn error of metal metabolism
description: >-
  Congenital atransferrinemia, also called familial hypotransferrinemia, is a rare autosomal recessive TF-related
  disorder with markedly reduced circulating transferrin. Reduced transferrin-mediated iron delivery commonly
  causes microcytic hypochromic anemia in childhood, while disturbed iron sensing and low hepcidin can promote
  non-transferrin-bound iron accumulation in parenchymal organs. Cardiac, hepatic and endocrine injury can
  be severe. The spectrum also includes adult-onset iron overload with mild or absent anemia. Residual transferrin,
  age, treatment and other modifiers complicate genotype-phenotype prediction; neither a universal transferrin
  threshold nor complete clinical penetrance is established. Management replaces transferrin when needed, controls
  iron overload according to anemia tolerance, and monitors organ function.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  expressivity: VARIABLE
  description: >-
    Classic congenital disease is associated with homozygous or compound-heterozygous TF defects. Heterozygous
    relatives may have reduced transferrin without the severe childhood phenotype. Clinical expression varies
    substantially even at very low transferrin concentrations; the available kindreds do not establish complete
    penetrance or exclude modifier effects.
  evidence:
  - reference: PMID:11110675
    reference_title: Molecular characterization of a case of atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Each of the patient's transferrin genes contains one mutation, ie, the patient is a compound heterozygote
      for these mutations, because one was found in each of her parents.
    explanation: >-
      Segregation of the two parental alleles supports recessive transmission.
  - &id001
    reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Interestingly, although serum transferrin was similar to previously described cases, anemia was mild
      in the index patient, and was absent in her sister.
    explanation: >-
      Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance
      estimate.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    The 2018 follow-up cited only 16 published cases at that time. Later families and overlapping follow-up
    reports preclude treating that historical count as a current total or deriving population prevalence.
  evidence:
  - reference: PMID:28895280
    reference_title: 'Addition of oral iron to plasma transfusion in human congenital hypotransferrinemia: A 10-year observational follow-up with the effects on hematological parameters and growth.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Since its description in 1961, only 16 cases have been reported.
    explanation: >-
      Historical literature count in a case follow-up, not a population denominator or current cumulative
      count.
    quote_role: BACKGROUND
genetic:
- name: TF
  gene_term:
    preferred_term: TF
    term:
      id: hgnc:11740
      label: TF
  relationship_type: CAUSATIVE
  notes: >-
    TF encodes the major plasma iron carrier. Recessive defects can markedly lower circulating protein, but
    individual missense alleles should not all be assigned the same folding, secretion or iron-binding mechanism
    without functional evidence. The US compound-heterozygous p.Ala477Pro and deletion-insertion case and
    Turkish p.Cys137Tyr case are reported primary examples. The adult p.Glu370Lys family broadens the clinical
    spectrum. A newly reported intronic deletion remains a VUS despite a compatible phenotype. A broader
    hereditary hypotransferrinemia series also described HFE/HAMP or acquired cofactors; those selected cases
    do not establish that every carrier develops overload.
  variants:
  - name: TF p.Ala477Pro with a second deletion-insertion allele
    description: 'The first molecularly characterized US case had two different alleles: p.Ala477Pro and a 10-bp deletion with 9-bp insertion. Segregation and conservation supported causality; the accessible abstract does not report a secretion assay.'
  - name: TF p.Cys137Tyr
    description: Exon-4 c.410G>A was reported in the Turkish case subsequently followed under plasma plus iron treatment; these publications concern one patient.
  - name: TF p.Glu370Lys
    description: Homozygous c.1108G>A in two adult sisters with severe hypotransferrinemia and iron overload; classified as likely pathogenic by the 2025 authors using prediction and segregation, without a reported functional assay.
  - name: TF c.2063-11_2063-10del
    description: A homozygous intronic variant in a 13-year-old with anemia, cardiac/hepatic iron and diabetes. The source explicitly classifies it as a variant of uncertain significance; rarity and segregation do not establish a splice defect.
  evidence:
  - reference: PMID:11110675
    reference_title: Molecular characterization of a case of atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Hereditary atransferrinemia is a rare but instructive disorder that has previously been reported
      in only 8 patients in 6 families. It is characterized by microcytic anemia and by iron loading, and
      can be treated effectively by plasma infusions. We now report the first case known in the United
      States. We determined the sequences flanking the exons of the human transferrin gene and sequenced
      all of the exons and some of the flanking regions of the patient's DNA and that of her parents. The
      patient's DNA revealed a 10-base pair (bp) deletion, followed by a 9-bp insertion of a duplicated
      sequence. There was also a G-->C transversion at complementary DNA (cDNA) nt 1429, predicting that
      a proline was substituted for the alanine in amino acid position 477 (Ala 477 Pro). The latter mutation
      occurs at an evolutionarily highly conserved site; 704 control alleles were screened and this point
      mutation was not found. Each of the patient's transferrin genes contains one mutation, ie, the patient
      is a compound heterozygote for these mutations, because one was found in each of her parents. In
      addition to these mutations, which we regard to be causative in the patient's atransferrinemia, a
      silent polymorphism at cDNA 1572 G-->C was found in exon 13 as well as 2 previously unreported polymorphisms
      at IVS8 + 62 c-->t and IVS14-4 c-->a. The mutation in nt 1572 and that in intron 8 were common in
      the general population; the intron 14 mutation is rare.
    explanation: >-
      Molecular characterization and familial segregation support two distinct TF alleles; benign polymorphisms
      described in the same abstract are not causal variants.
  - reference: PMID:18097132
    reference_title: A new case of human atransferrinemia with a previously undescribed mutation in the transferrin gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      DNA analysis of the serum transferrin gene in the patient revealed a previously undescribed mutation
      in exon 4, a G-->A transition at cDNA 410(Cys137Tyr).
    explanation: >-
      Primary case variant identification.
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Genetic analysis revealed homozygous TF variant NM_001063.3:c.1108G>A , p.(Glu370Lys). No other variants
      were found in the gene panel.
    explanation: >-
      Targeted panel result from one family; does not exclude every modifier outside the tested panel.
  - &id009
    reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Targeted exome sequencing in the proband revealed a novel splice site variant, NC_000003.12:g.133778575_133778576del(NM_001063.3:c.2063-11_2063-10del)
      in intron 16 of TF in the homozygous state. Segregation analysis in the mother confirmed the variant
      to be present in the heterozygous state. This variant was not observed in population databases and
      in-house whole-exome sequencing (WES) data of 1246 individuals of Indian origin (Fig 7). This variant
      has been classified as a variant of uncertain significance according to the American College of Medical
      Genetics and Genomics (ACMG) guidelines.
    explanation: >-
      The source explicitly labels the intronic variant uncertain. No RNA or expression experiment proves
      altered splicing.
  - reference: PMID:25486930
    reference_title: Hereditary hypotransferrinemia can lead to elevated transferrin saturation and, when associated to HFE or HAMP mutations, to iron overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      We show that, besides increasing serum transferrin saturation without iron overload, hypotransferrinemia,
      when associated to mutations in HFE or HAMP or to acquired factors, can lead to clinically relevant
      iron burden.
    explanation: >-
      Broader hereditary hypotransferrinemia series supports modifier-dependent iron burden; its duplicated
      abstract is the actual available content despite the full_text_html cache label. It does not establish
      the genotype distribution or severe anemia penetrance.
pathophysiology:
- name: Biallelic TF Defect
  biological_scale: MOLECULAR
  description: >-
    Pathogenic TF alleles reduce the availability of functional circulating transferrin through allele-dependent
    mechanisms. Genotype alone does not establish a universal protein-folding defect.
  evidence:
  - reference: PMID:11110675
    reference_title: Molecular characterization of a case of atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Hereditary atransferrinemia is a rare but instructive disorder that has previously been reported
      in only 8 patients in 6 families. It is characterized by microcytic anemia and by iron loading, and
      can be treated effectively by plasma infusions. We now report the first case known in the United
      States. We determined the sequences flanking the exons of the human transferrin gene and sequenced
      all of the exons and some of the flanking regions of the patient's DNA and that of her parents. The
      patient's DNA revealed a 10-base pair (bp) deletion, followed by a 9-bp insertion of a duplicated
      sequence. There was also a G-->C transversion at complementary DNA (cDNA) nt 1429, predicting that
      a proline was substituted for the alanine in amino acid position 477 (Ala 477 Pro). The latter mutation
      occurs at an evolutionarily highly conserved site; 704 control alleles were screened and this point
      mutation was not found. Each of the patient's transferrin genes contains one mutation, ie, the patient
      is a compound heterozygote for these mutations, because one was found in each of her parents. In
      addition to these mutations, which we regard to be causative in the patient's atransferrinemia, a
      silent polymorphism at cDNA 1572 G-->C was found in exon 13 as well as 2 previously unreported polymorphisms
      at IVS8 + 62 c-->t and IVS14-4 c-->a. The mutation in nt 1572 and that in intron 8 were common in
      the general population; the intron 14 mutation is rare.
    explanation: >-
      Molecular characterization and familial segregation support two distinct TF alleles; benign polymorphisms
      described in the same abstract are not causal variants.
  - reference: PMID:18097132
    reference_title: A new case of human atransferrinemia with a previously undescribed mutation in the transferrin gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      DNA analysis of the serum transferrin gene in the patient revealed a previously undescribed mutation
      in exon 4, a G-->A transition at cDNA 410(Cys137Tyr).
    explanation: >-
      Primary case variant identification.
  role: trigger
  downstream:
  - target: Reduced Circulating Transferrin
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Recessive TF defects can markedly reduce circulating protein; the precise expression or processing
      defect varies by allele.
    evidence:
    - reference: PMID:11110675
      reference_title: Molecular characterization of a case of atransferrinemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        Hereditary atransferrinemia is a rare but instructive disorder that has previously been reported
        in only 8 patients in 6 families. It is characterized by microcytic anemia and by iron loading,
        and can be treated effectively by plasma infusions. We now report the first case known in the
        United States. We determined the sequences flanking the exons of the human transferrin gene and
        sequenced all of the exons and some of the flanking regions of the patient's DNA and that of
        her parents. The patient's DNA revealed a 10-base pair (bp) deletion, followed by a 9-bp insertion
        of a duplicated sequence. There was also a G-->C transversion at complementary DNA (cDNA) nt
        1429, predicting that a proline was substituted for the alanine in amino acid position 477 (Ala
        477 Pro). The latter mutation occurs at an evolutionarily highly conserved site; 704 control
        alleles were screened and this point mutation was not found. Each of the patient's transferrin
        genes contains one mutation, ie, the patient is a compound heterozygote for these mutations,
        because one was found in each of her parents. In addition to these mutations, which we regard
        to be causative in the patient's atransferrinemia, a silent polymorphism at cDNA 1572 G-->C was
        found in exon 13 as well as 2 previously unreported polymorphisms at IVS8 + 62 c-->t and IVS14-4
        c-->a. The mutation in nt 1572 and that in intron 8 were common in the general population; the
        intron 14 mutation is rare.
      explanation: >-
        Molecular characterization and familial segregation support two distinct TF alleles; benign polymorphisms
        described in the same abstract are not causal variants.
      directness: INDIRECT
- name: Reduced Circulating Transferrin
  biological_scale: MOLECULAR
  description: >-
    Severely reduced plasma transferrin limits iron-binding capacity and iron delivery, although trace protein
    and clinical expression vary.
  evidence:
  - reference: PMID:11920219
    reference_title: Biochemical and genetic defects underlying human congenital hypotransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      At diagnosis the patient had serum Tf levels equal to about 1% of the normal values.
    explanation: >-
      Biochemical measurement in a single congenital case.
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Interestingly, although serum transferrin was similar to previously described cases, anemia was mild
      in the index patient, and was absent in her sister.
    explanation: >-
      Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance
      estimate.
  downstream:
  - target: Reduced Erythroid Iron Delivery
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Lower transferrin availability reduces receptor-mediated erythroid iron supply; this is not absolute
      cessation of all erythroid iron uptake.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency
        of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral
        tissues (secondary hemochromatosis) [4].
      explanation: >-
        Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific
        transport assay.
      directness: INDIRECT
  - target: Reduced Transferrin-Dependent Hepcidin Stimulation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Loss of circulating transferrin can weaken the iron-sensing input to hepatic hepcidin regulation.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        These results suggest that hepcidin expression in hpx mice is regulated both by Tf-restricted
        erythropoiesis and by Tf through a mechanism independent of its role in erythropoiesis.
      explanation: >-
        Interpretation of perturbation experiments in hpx mice.
      directness: INDIRECT
  - target: Non-Transferrin-Bound Iron Accumulation
    causal_link_type: DIRECT
    description: >-
      Reduced binding capacity limits safe carriage of circulating iron.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        They exhibit high saturation of residual transferrin with iron and accumulate NTBI.
      explanation: >-
        Clinical review of congenital disease.
      directness: DIRECT
    - reference: PMID:40112917
      reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L
        (N:<0.5).
      explanation: >-
        Measured iron indices in the nonanemic adult sister.
      directness: DIRECT
  - target: Atransferrinemia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reduced circulating transferrin manifests in this laboratory measurement.
    evidence:
    - reference: PMID:11920219
      reference_title: Biochemical and genetic defects underlying human congenital hypotransferrinemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        At diagnosis the patient had serum Tf levels equal to about 1% of the normal values.
      explanation: >-
        Severe measured transferrin deficiency in a congenital case.
      directness: INDIRECT
  - target: Decreased Total Iron-Binding Capacity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reduced circulating transferrin manifests in this laboratory measurement.
    evidence:
    - reference: PMID:19579082
      reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient
      explanation: Documents the reduced TIBC that, with low serum iron and high ferritin, forms the disorder's biochemical signature.
      quote_role: PRIMARY_RESULT
      directness: INDIRECT
- name: Reduced Erythroid Iron Delivery
  biological_scale: CELLULAR
  description: >-
    Loss of transferrin-mediated delivery restricts iron available to erythroid precursors in the classic
    anemic phenotype. Alternative uptake or residual transferrin may sustain erythropoiesis in some patients.
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency
      of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral
      tissues (secondary hemochromatosis) [4].
    explanation: >-
      Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific
      transport assay.
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Interestingly, although serum transferrin was similar to previously described cases, anemia was mild
      in the index patient, and was absent in her sister.
    explanation: >-
      Two adult sisters with homozygous TF p.Glu370Lys had different anemia expression; this is not a penetrance
      estimate.
  cell_types:
  - preferred_term: erythroblast
    term:
      id: CL:0000765
      label: erythroblast
  downstream:
  - target: Reduced Hemoglobin Synthesis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Iron is required for heme and hemoglobin synthesis; reduced supply limits production.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency
        of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral
        tissues (secondary hemochromatosis) [4].
      explanation: >-
        Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific
        transport assay.
      directness: INDIRECT
- name: Reduced Hemoglobin Synthesis
  biological_scale: CELLULAR
  description: >-
    Iron restriction impairs hemoglobin production, accounting for hypochromic microcytosis in many childhood
    cases.
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      TF binds and delivers trivalent iron to erythroid precursors for synthesis of hemoglobin. Deficiency
      of TF leads to reduced hemoglobin synthesis and anemia, but with excess iron stored in peripheral
      tissues (secondary hemochromatosis) [4].
    explanation: >-
      Clinical background explains iron-restricted hemoglobin production; this is not a patient-specific
      transport assay.
  downstream:
  - target: Hypochromic Microcytic Anemia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Reduced hemoglobin production produces the classic anemia phenotype, with variable expression across
      the TF-related spectrum.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and
        iron overload in parenchymal cells of the liver, heart and pancreas.
      explanation: >-
        Clinical review describes the classic phenotype; later familial observations establish that severe
        childhood anemia is not universal.
      directness: INDIRECT
  - target: Increased Erythropoietic Drive
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Anemia can increase erythropoietic drive through systemic compensatory signals; this branch is not
      present in every nonanemic patient.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        Transfusion of hpx animals with wild-type red blood cells led to increased hepcidin expression,
        while hepcidin expression in myeloablated hpx mice increased only if Tf was administered postablation.
      explanation: >-
        Mouse perturbations distinguish erythropoietic and transferrin-dependent contributions; they
        do not identify a single human mediator.
      directness: INDIRECT
  - target: Pallor
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The classic iron-restricted anemia can contribute to this finding, without establishing universal
      occurrence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue,
        anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent
        infections.
      explanation: >-
        Background clinical spectrum; these manifestations were not all observed in the two reported
        children.
      directness: INDIRECT
  - target: Fatigue
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The classic iron-restricted anemia can contribute to this finding, without establishing universal
      occurrence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue,
        anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent
        infections.
      explanation: >-
        Background clinical spectrum; these manifestations were not all observed in the two reported
        children.
      directness: INDIRECT
  - target: Growth Delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The classic iron-restricted anemia can contribute to this finding, without establishing universal
      occurrence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue,
        anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent
        infections.
      explanation: >-
        Background clinical spectrum; these manifestations were not all observed in the two reported
        children.
      directness: INDIRECT
  - target: Tachycardia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The classic iron-restricted anemia can contribute to this finding, without establishing universal
      occurrence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue,
        anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent
        infections.
      explanation: >-
        Background clinical spectrum; these manifestations were not all observed in the two reported
        children.
      directness: INDIRECT
  - target: Heart Murmur
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The classic iron-restricted anemia can contribute to this finding, without establishing universal
      occurrence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue,
        anorexia, irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent
        infections.
      explanation: >-
        Background clinical spectrum; these manifestations were not all observed in the two reported
        children.
      directness: INDIRECT
- name: Increased Erythropoietic Drive
  biological_scale: CELLULAR
  description: >-
    Anemic transferrin-deficient patients and mice can increase erythroid demand. This does not by itself
    prove apoptotic ineffective erythropoiesis, and embryonic fish regulate hepcidin differently.
  evidence:
  - reference: PMID:20956801
    reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      Transfusion of hpx animals with wild-type red blood cells led to increased hepcidin expression, while
      hepcidin expression in myeloablated hpx mice increased only if Tf was administered postablation.
    explanation: >-
      Mouse perturbations distinguish erythropoietic and transferrin-dependent contributions; they do not
      identify a single human mediator.
  downstream:
  - target: Reduced Hepcidin Production
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Erythropoietic demand can suppress hepcidin in the postnatal mammalian setting; the cited experiments
      do not identify erythroferrone as the necessary mediator.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        Transfusion of hpx animals with wild-type red blood cells led to increased hepcidin expression,
        while hepcidin expression in myeloablated hpx mice increased only if Tf was administered postablation.
      explanation: >-
        Mouse perturbations distinguish erythropoietic and transferrin-dependent contributions; they
        do not identify a single human mediator.
      directness: INDIRECT
- name: Reduced Transferrin-Dependent Hepcidin Stimulation
  biological_scale: MOLECULAR
  description: >-
    Transferrin also supports hepcidin regulation independently of its immediate erythroid-delivery role.
    Mouse and embryonic fish experiments support this branch; the complete receptor-to-transcription sequence
    is not established by those experiments.
  evidence:
  - &id011
    reference: PMID:20956801
    reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      These results suggest that hepcidin expression in hpx mice is regulated both by Tf-restricted erythropoiesis
      and by Tf through a mechanism independent of its role in erythropoiesis.
    explanation: >-
      Interpretation of perturbation experiments in hpx mice.
  downstream:
  - target: Reduced Hepcidin Production
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reduced transferrin-dependent signaling contributes to lower hepcidin expression.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        These results suggest that hepcidin expression in hpx mice is regulated both by Tf-restricted
        erythropoiesis and by Tf through a mechanism independent of its role in erythropoiesis.
      explanation: >-
        Interpretation of perturbation experiments in hpx mice.
      directness: INDIRECT
- name: Reduced Hepcidin Production
  biological_scale: MOLECULAR
  description: >-
    Hepcidin can remain low despite systemic iron overload. A human longitudinal plasma-transfusion study
    measured changing urinary hepcidin; it did not directly quantify hepatic transcription or prove a specific
    receptor interaction.
  evidence:
  - &id010
    reference: PMID:17768112
    reference_title: Effects of plasma transfusion on hepcidin production in human congenital hypotransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Urinary hepcidin increased from zero at baseline, when hemoglobin and serum transferrin was low,
      to a maximum of 98 ng/mg creatinine on day 60, and subsequently decreased.
    explanation: >-
      Longitudinal urinary-hepcidin measurements in one plasma-treated child.
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Hepcidin is suppressed due to increased erythropoietic drive (115), which is consistent with the
      increased iron absorption in spite of iron overload.
    explanation: >-
      Review synthesis of the classic transferrin-deficient iron-loading phenotype.
  downstream:
  - target: Reduced Ferroportin Downregulation
    causal_link_type: DIRECT
    description: >-
      Less hepcidin permits more ferroportin to remain available for iron export.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other
        target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin
        in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption
        is inhibited, and plasma iron levels drop.
      explanation: >-
        Established hepcidin-ferroportin physiology, interpreted within the disorder.
      directness: DIRECT
- name: Reduced Ferroportin Downregulation
  biological_scale: MOLECULAR
  description: >-
    Low hepcidin reduces the signal that normally internalizes and degrades ferroportin. This applies established
    iron-regulatory physiology to atransferrinemia rather than reporting a patient ferroportin assay.
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other
      target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin
      in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption is
      inhibited, and plasma iron levels drop.
    explanation: >-
      Established hepcidin-ferroportin physiology, interpreted within the disorder.
  downstream:
  - target: Increased Iron Entry into Plasma
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Failure to downregulate iron export increases plasma iron flux from enterocytes and recycling cells.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other
        target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin
        in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption
        is inhibited, and plasma iron levels drop.
      explanation: >-
        Established hepcidin-ferroportin physiology, interpreted within the disorder.
      directness: INDIRECT
- name: Increased Iron Entry into Plasma
  biological_scale: CELLULAR
  description: >-
    Persistent ferroportin-mediated export favors dietary iron absorption and release of recycled iron despite
    parenchymal overload.
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Hepcidin is suppressed due to increased erythropoietic drive (115), which is consistent with the
      increased iron absorption in spite of iron overload.
    explanation: >-
      Review synthesis of the classic transferrin-deficient iron-loading phenotype.
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Hepcidin operates by binding to ferroportin in tissue macrophages, duodenal enterocytes and other
      target cells (Figure 1). This triggers ubiquitination, internalization and degradation of ferroportin
      in lysosomes (5). As a result, iron is sequestered within macrophages, dietary iron absorption is
      inhibited, and plasma iron levels drop.
    explanation: >-
      Established hepcidin-ferroportin physiology, interpreted within the disorder.
  downstream:
  - target: Non-Transferrin-Bound Iron Accumulation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Increased iron flux can exceed the reduced available transferrin-binding capacity.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        They exhibit high saturation of residual transferrin with iron and accumulate NTBI.
      explanation: >-
        Clinical review of congenital disease.
      directness: INDIRECT
    - reference: PMID:40112917
      reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L
        (N:<0.5).
      explanation: >-
        Measured iron indices in the nonanemic adult sister.
      directness: INDIRECT
- name: Non-Transferrin-Bound Iron Accumulation
  biological_scale: MOLECULAR
  description: >-
    Very low transferrin-binding capacity permits non-transferrin-bound iron to circulate. Calculated transferrin
    saturation can be high or exceed 100% when transferrin is extremely low; it is not a universal low-saturation
    disorder.
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      They exhibit high saturation of residual transferrin with iron and accumulate NTBI.
    explanation: >-
      Clinical review of congenital disease.
  - &id008
    reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Her ferritin was 1408µg/L, transferrin saturation 100%, serum transferrin 0.3 g/L, and NTBI 1.3µmol/L
      (N:<0.5).
    explanation: >-
      Measured iron indices in the nonanemic adult sister.
  downstream:
  - target: Parenchymal Iron Accumulation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Non-transferrin iron uptake promotes tissue loading; specific transporter necessity is not established
      in the human reports.
    evidence:
    - reference: PMID:30420953
      reference_title: Inherited Disorders of Iron Overload.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and
        iron overload in parenchymal cells of the liver, heart and pancreas.
      explanation: >-
        Clinical review describes the classic phenotype; later familial observations establish that severe
        childhood anemia is not universal.
      directness: INDIRECT
- name: Parenchymal Iron Accumulation
  biological_scale: TISSUE
  description: >-
    Nonerythroid organs take up iron despite iron-restricted erythropoiesis. Hepatic and myocardial iron
    can be measured directly; the responsible uptake routes differ by tissue.
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and iron
      overload in parenchymal cells of the liver, heart and pancreas.
    explanation: >-
      Clinical review describes the classic phenotype; later familial observations establish that severe
      childhood anemia is not universal.
  - &id002
    reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      T2* quantification estimated a cardiac iron concentration of 5.3 mg/g (normal <1 mg/g) and hepatic
      iron concentration of 17.8 mg/g (normal 0.8-1.16 mg/g), confirming severe iron overload.
    explanation: >-
      MRI iron quantification in the clinically affected child; its TF allele remains a VUS.
  downstream:
  - target: Iron-Associated Oxidative Injury
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      The labile iron fraction can promote oxidative injury; MRI total iron does not measure that fraction
      or its molecular flux.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        These radicals cause lipid peroxidation, nucleic acid damage, and protein dysfunction, disrupting
        cellular antioxidant defenses.
      explanation: >-
        General iron-overload mechanism summarized in the clinical review, not an assay of the reported
        patient.
      directness: INDIRECT
  - target: Elevated Hepatic Iron
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Tissue iron accumulation is associated with this iron-status measurement; ferritin is also influenced
      by inflammation and other conditions.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        T2* quantification estimated a cardiac iron concentration of 5.3 mg/g (normal <1 mg/g) and hepatic
        iron concentration of 17.8 mg/g (normal 0.8-1.16 mg/g), confirming severe iron overload.
      explanation: >-
        MRI iron quantification in the clinically affected child; its TF allele remains a VUS.
      directness: INDIRECT
  - target: Elevated Serum Ferritin
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Tissue iron accumulation is associated with this iron-status measurement; ferritin is also influenced
      by inflammation and other conditions.
    evidence:
    - reference: PMID:19579082
      reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient
      explanation: Documents the elevated serum ferritin reflecting body iron overload despite the concurrent anemia.
      quote_role: PRIMARY_RESULT
      directness: INDIRECT
  - target: Diabetes Mellitus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve
      a patient-specific causal sequence.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
        and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at
        age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated
        ferritin, low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography
        showed severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA
        (Fig. 4). As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed
        myocardial iron overload, and genetic testing identified a novel mutation, confirming the diagnosis.
        This highlights the importance of early recognition and genetic analysis in hereditary atransferrinemia.
      explanation: >-
        Primary clinical case embedded in a review. Its intronic TF variant is later classified as a
        VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
      directness: INDIRECT
  - target: Hypothyroidism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve
      a patient-specific causal sequence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
  - target: Hypoparathyroidism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve
      a patient-specific causal sequence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
  - target: Cardiac Arrhythmia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Organ iron injury can contribute to this complication, but the cited clinical sources do not resolve
      a patient-specific causal sequence.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
- name: Iron-Associated Oxidative Injury
  biological_scale: CELLULAR
  description: >-
    Redox-active iron can generate reactive species and damage membranes, proteins and nucleic acids. The
    cited review draws this mechanism from broader iron-overload cardiomyopathy; it was not directly measured
    in the atransferrinemic child.
  evidence:
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      These radicals cause lipid peroxidation, nucleic acid damage, and protein dysfunction, disrupting
      cellular antioxidant defenses.
    explanation: >-
      General iron-overload mechanism summarized in the clinical review, not an assay of the reported patient.
  downstream:
  - target: Myocardial Dysfunction
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Oxidative injury and altered calcium handling may contribute to dysfunction; human case evidence
      does not isolate this sequence.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        These radicals cause lipid peroxidation, nucleic acid damage, and protein dysfunction, disrupting
        cellular antioxidant defenses.
      explanation: >-
        General iron-overload mechanism summarized in the clinical review, not an assay of the reported
        patient.
      directness: INDIRECT
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
        and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at
        age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated
        ferritin, low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography
        showed severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA
        (Fig. 4). As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed
        myocardial iron overload, and genetic testing identified a novel mutation, confirming the diagnosis.
        This highlights the importance of early recognition and genetic analysis in hereditary atransferrinemia.
      explanation: >-
        Primary clinical case embedded in a review. Its intronic TF variant is later classified as a
        VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
      directness: INDIRECT
  - target: Hepatic Fibrotic Injury
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Chronic iron-related injury can provoke hepatic fibrogenic repair, although this sequence was not
      experimentally tested in the reported patients.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
- name: Myocardial Dysfunction
  biological_scale: TISSUE
  description: >-
    Iron-associated injury can impair myocardial function. The relative roles of iron toxicity and anemia-related
    circulatory demand vary and are not isolated by the case reports.
  evidence:
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
      and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age
      seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,
      low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography showed
      severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA (Fig. 4).
      As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed myocardial
      iron overload, and genetic testing identified a novel mutation, confirming the diagnosis. This highlights
      the importance of early recognition and genetic analysis in hereditary atransferrinemia.
    explanation: >-
      Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS,
      so the phenotype is clinically consistent but the allele is not functionally confirmed.
  downstream:
  - target: Cardiomyopathy
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Impaired myocardial function can manifest clinically in this form.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
        and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at
        age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated
        ferritin, low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography
        showed severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA
        (Fig. 4). As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed
        myocardial iron overload, and genetic testing identified a novel mutation, confirming the diagnosis.
        This highlights the importance of early recognition and genetic analysis in hereditary atransferrinemia.
      explanation: >-
        Primary clinical case embedded in a review. Its intronic TF variant is later classified as a
        VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
      directness: INDIRECT
  - target: Heart Failure
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Impaired myocardial function can manifest clinically in this form.
    evidence:
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
        and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at
        age seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated
        ferritin, low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography
        showed severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA
        (Fig. 4). As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed
        myocardial iron overload, and genetic testing identified a novel mutation, confirming the diagnosis.
        This highlights the importance of early recognition and genetic analysis in hereditary atransferrinemia.
      explanation: >-
        Primary clinical case embedded in a review. Its intronic TF variant is later classified as a
        VUS, so the phenotype is clinically consistent but the allele is not functionally confirmed.
      directness: INDIRECT
- name: Hepatic Fibrotic Injury
  biological_scale: TISSUE
  description: >-
    Chronic hepatic iron injury can be accompanied by fibrosis and cirrhosis; not every patient with MRI
    iron has established fibrosis.
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
  - &id003
    reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      CT workup revealed cirrhosis with ascites.
    explanation: >-
      Cirrhosis was observed in the adult index case with later documented severe iron overload.
  downstream:
  - target: Hepatic Fibrosis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Hepatic fibrotic injury can produce this clinical or pathological finding.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
  - target: Cirrhosis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Hepatic fibrotic injury can produce this clinical or pathological finding.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: >-
        Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
        like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
      explanation: >-
        Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
        organ sequence is established.
      directness: INDIRECT
    - reference: PMID:40112917
      reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        CT workup revealed cirrhosis with ascites.
      explanation: >-
        Cirrhosis was observed in the adult index case with later documented severe iron overload.
      directness: INDIRECT
phenotypes:
- name: Hypochromic Microcytic Anemia
  category: Laboratory
  description: >-
    The classic childhood presentation is iron-refractory hypochromic microcytic anemia. Adult relatives
    with profound hypotransferrinemia may have mild normocytic anemia or no anemia; age and anemia severity
    are not obligatory.
  phenotype_term:
    preferred_term: Hypochromic microcytic anemia
    term:
      id: HP:0004840
      label: Hypochromic microcytic anemia
  evidence:
  - &id007
    reference: PMID:19579082
    reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Further evaluations indicate severe hypochromic microcytic anemia with decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient. The serum level of transferrin was decreased.
    explanation: Directly documents the severe hypochromic microcytic anemia with the characteristic low iron/TIBC and high ferritin laboratory pattern.
    quote_role: PRIMARY_RESULT
  - *id001
- name: Atransferrinemia
  category: Laboratory
  description: >-
    Markedly reduced circulating transferrin; apparently undetectable immunoassay results do not establish
    absolute protein absence.
  phenotype_term:
    preferred_term: Atransferrinemia
    term:
      id: HP:0012239
      label: Atransferrinemia
  evidence:
  - reference: PMID:11920219
    reference_title: Biochemical and genetic defects underlying human congenital hypotransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      At diagnosis the patient had serum Tf levels equal to about 1% of the normal values.
    explanation: >-
      Severe measured transferrin deficiency in a congenital case.
- name: Decreased Serum Iron
  category: Laboratory
  description: Low serum iron with reduced total iron-binding capacity.
  phenotype_term:
    preferred_term: Decreased circulating iron concentration
    term:
      id: HP:0040303
      label: Decreased circulating iron concentration
  evidence:
  - reference: PMID:19579082
    reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient
    explanation: Documents the low serum iron of the characteristic iron-study pattern.
    quote_role: PRIMARY_RESULT
- name: Decreased Total Iron-Binding Capacity
  category: Laboratory
  description: Reduced total iron-binding capacity, reflecting the near-absence of circulating transferrin (its principal determinant).
  phenotype_term:
    preferred_term: Decreased total iron binding capacity
    term:
      id: HP:0033211
      label: Decreased total iron binding capacity
  evidence:
  - reference: PMID:19579082
    reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient
    explanation: Documents the reduced TIBC that, with low serum iron and high ferritin, forms the disorder's biochemical signature.
    quote_role: PRIMARY_RESULT
- name: Elevated Serum Ferritin
  category: Laboratory
  description: Elevated serum ferritin reflecting tissue iron overload.
  phenotype_term:
    preferred_term: Increased circulating ferritin concentration
    term:
      id: HP:0003281
      label: Increased circulating ferritin concentration
  evidence:
  - reference: PMID:19579082
    reference_title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: decreased serum levels of iron, TIBC, and increased serum level of ferritin in this patient
    explanation: Documents the elevated serum ferritin reflecting body iron overload despite the concurrent anemia.
    quote_role: PRIMARY_RESULT
- name: Elevated Hepatic Iron
  category: Laboratory
  phenotype_term:
    preferred_term: Elevated hepatic iron concentration
    term:
      id: HP:0012465
      label: Elevated hepatic iron concentration
  description: >-
    Hepatic iron overload measured by MRI or other validated tissue-iron methods; normal liver enzymes do
    not exclude it.
  evidence:
  - *id002
- name: Pallor
  category: Clinical
  phenotype_term:
    preferred_term: Pallor
    term:
      id: HP:0000980
      label: Pallor
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Fatigue
  category: Clinical
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Growth Delay
  category: Clinical
  description: >-
    Growth delay is reported in the childhood spectrum; adequate growth is also described under treatment.
  phenotype_term:
    preferred_term: Growth delay
    term:
      id: HP:0001510
      label: Growth delay
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Recurrent Infections
  category: Clinical
  description: >-
    Recurrent infections are reported in clinical background summaries, without a reliable frequency or proof
    of a specific immune defect.
  phenotype_term:
    preferred_term: Recurrent infections
    term:
      id: HP:0002719
      label: Recurrent infections
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Cardiomyopathy
  category: Clinical
  description: Cardiac dysfunction from myocardial iron deposition.
  phenotype_term:
    preferred_term: Cardiomyopathy
    term:
      id: HP:0001638
      label: Cardiomyopathy
  evidence:
  - &id004
    reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
      and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age
      seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,
      low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography showed
      severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA (Fig. 4).
      As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed myocardial
      iron overload, and genetic testing identified a novel mutation, confirming the diagnosis. This highlights
      the importance of early recognition and genetic analysis in hereditary atransferrinemia.
    explanation: >-
      Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS,
      so the phenotype is clinically consistent but the allele is not functionally confirmed.
- name: Hepatomegaly
  category: Clinical
  phenotype_term:
    preferred_term: Hepatomegaly
    term:
      id: HP:0002240
      label: Hepatomegaly
  description: >-
    Observed in a clinically diagnosed child; the report does not establish the individual contribution of
    iron deposition versus other mechanisms.
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Examination revealed pallor and mild hepatosplenomegaly.
    explanation: >-
      Observed in the four-year-old girl, who had no molecular testing or subsequent treatment follow-up.
- name: Hepatic Fibrosis
  category: Clinical
  description: Late hepatic iron-overload complication.
  phenotype_term:
    preferred_term: Hepatic fibrosis
    term:
      id: HP:0001395
      label: Hepatic fibrosis
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
- name: Cirrhosis
  category: Clinical
  description: Advanced hepatic iron-overload complication.
  phenotype_term:
    preferred_term: Cirrhosis
    term:
      id: HP:0001394
      label: Cirrhosis
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
  - *id003
- name: Diabetes Mellitus
  category: Clinical
  description: Endocrine iron-overload complication (pancreatic iron deposition).
  phenotype_term:
    preferred_term: Diabetes mellitus
    term:
      id: HP:0000819
      label: Diabetes mellitus
  evidence:
  - *id004
- name: Hypothyroidism
  category: Clinical
  description: Endocrine iron-overload complication (thyroid iron deposition).
  phenotype_term:
    preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
- name: Splenomegaly
  category: Clinical
  phenotype_term:
    preferred_term: Splenomegaly
    term:
      id: HP:0001744
      label: Splenomegaly
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Examination revealed pallor and mild hepatosplenomegaly.
    explanation: >-
      Observed in the four-year-old girl, who had no molecular testing or subsequent treatment follow-up.
  description: >-
    Observed in a clinically diagnosed child; the report does not establish the individual contribution of
    iron deposition versus other mechanisms.
- name: Heart Failure
  category: Clinical
  description: >-
    Severe cardiac failure has occurred in children and in a late-presenting adult; no age-specific incidence
    is available.
  phenotype_term:
    preferred_term: Congestive heart failure
    term:
      id: HP:0001635
      label: Congestive heart failure
  evidence:
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
      and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age
      seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,
      low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography showed
      severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA (Fig. 4).
      As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed myocardial
      iron overload, and genetic testing identified a novel mutation, confirming the diagnosis. This highlights
      the importance of early recognition and genetic analysis in hereditary atransferrinemia.
    explanation: >-
      Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS,
      so the phenotype is clinically consistent but the allele is not functionally confirmed.
- name: Hypospadias
  category: Clinical
  description: >-
    A reported congenital finding in selected cases. Fetal hypoxia has been proposed, but a causal TF-to-genital-development
    mechanism is unproven.
  phenotype_term:
    preferred_term: Hypospadias
    term:
      id: HP:0000047
      label: Hypospadias
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Examination revealed pallor and coronal hypospadias (asymptomatic).
    explanation: >-
      Direct observation in one clinically diagnosed boy.
- name: Cardiac Arrhythmia
  category: Clinical
  description: >-
    Listed among possible iron-overload sequelae; no disease-specific denominator is available.
  phenotype_term:
    preferred_term: Arrhythmia
    term:
      id: HP:0011675
      label: Arrhythmia
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
- name: Hypoparathyroidism
  category: Clinical
  description: >-
    Secondary hypoparathyroidism is listed in clinical summaries of iron-overload complications.
  phenotype_term:
    preferred_term: Hypoparathyroidism
    term:
      id: HP:0000829
      label: Hypoparathyroidism
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Iron overload can lead to hepatic fibrosis, cirrhosis, arrhythmias, heart failure, and endocrinopathies
      like diabetes mellitus, secondary hypoparathyroidism and hypothyroidism.
    explanation: >-
      Background synthesis lists possible iron-overload complications; no cohort frequency or obligatory
      organ sequence is established.
- name: Tachycardia
  category: Clinical
  description: >-
    Reported with severe anemia; it is not specific to myocardial iron injury.
  phenotype_term:
    preferred_term: Tachycardia
    term:
      id: HP:0001649
      label: Tachycardia
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Heart Murmur
  category: Clinical
  description: >-
    Systolic murmur is described with severe anemia; the source does not establish structural valve disease.
  phenotype_term:
    preferred_term: Heart murmur
    term:
      id: HP:0030148
      label: Heart murmur
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Manifestations of severe anemia develop in infancy or early childhood, i.e. pallor, fatigue, anorexia,
      irritability, tachycardia, systolic murmur, hepatomegaly, growth retardation and recurrent infections.
    explanation: >-
      Background clinical spectrum; these manifestations were not all observed in the two reported children.
- name: Poor Appetite
  category: Clinical
  description: >-
    Poor oral intake or anorexia can accompany childhood presentation.
  phenotype_term:
    preferred_term: Poor appetite
    term:
      id: HP:0004396
      label: Poor appetite
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      A 4-year-old girl, born of non consanguineous marriage was apparently well till 10 months of age,
      when her parents noticed pallor and lethargy with poor oral intake.
    explanation: >-
      Primary case observation.
- name: Failure to Thrive
  category: Clinical
  description: >-
    Reported in the childhood spectrum; treatment can support subsequent growth and this is not obligatory
    in adult presentations.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Affected children may show a failure to thrive with occasional retardation in mental development.
    explanation: >-
      Clinical synthesis in the 2014 guideline; developmental assessment methods and a phenotype denominator
      are not supplied.
- name: Neurodevelopmental Delay
  category: Clinical
  description: >-
    The guideline describes delayed mental development in some children without formal domain or IQ details;
    intellectual disability is not inferred from that wording.
  phenotype_term:
    preferred_term: Neurodevelopmental delay
    term:
      id: HP:0012758
      label: Neurodevelopmental delay
  evidence:
  - reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Affected children may show a failure to thrive with occasional retardation in mental development.
    explanation: >-
      Clinical synthesis in the 2014 guideline; developmental assessment methods and a phenotype denominator
      are not supplied.
- name: Osteoporosis
  category: Clinical
  description: >-
    Reported in some patients in clinical synthesis, without a reliable frequency or an established single
    mechanism.
  phenotype_term:
    preferred_term: Osteoporosis
    term:
      id: HP:0000939
      label: Osteoporosis
  evidence:
  - reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      skin iron deposition, and sometimes fatal cardiomyopathy. Some patients have osteoporosis.
    explanation: >-
      The guideline identifies this complication; its exact prevalence and mediation are not established.
treatments:
- name: Plasma transferrin replacement
  description: >-
    Plasma infusions supply transferrin and can improve iron-restricted erythropoiesis. Dose and interval
    are individualized to hemoglobin, transferrin and clinical course; a fixed monthly schedule may become
    insufficient during growth. Case reports do not establish uniform tissue-iron clearance or comparative
    product efficacy.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Fresh Frozen Plasma Transfusion
    term:
      id: NCIT:C116475
      label: Fresh Frozen Plasma Transfusion
  evidence:
  - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
    reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine,
      hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig
      ervaring).
    explanation: >-
      The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting
      limited apotransferrin experience. Its evidence base consists of small case reports.
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The patient has responded to treatment regimen of monthly infusions of fresh frozen plasma (FFP),
      with an increase of reticulocyte count to 6% at 2 weeks, Hb rise to 12.4 mg/dL at 1 month and decline
      of serum ferritin to 903 µg/L after 12 months.
    explanation: >-
      Response was documented in the boy only; the girl was lost to follow-up. The quoted hemoglobin unit
      is the source’s typographical error and is not used as a dose or treatment target.
  - reference: PMID:17768112
    reference_title: Effects of plasma transfusion on hepcidin production in human congenital hypotransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Hemoglobin pr ogressively increased reaching normal values during the third month.
    explanation: >-
      Response to intensified plasma replacement in one child; plasma volume and frequency changed together.
  - &id005
    reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Transferrin supplementation by either plasma transfusion or apotransferrin infusion is recommended
      in patients with hypotransferrinemia due to a TF defect.
    explanation: >-
      Disease-specific recommendation from Donker et al. 2014 (PMID:24665134), whose evidence base is mainly
      case reports and small series.
  target_mechanisms:
  - target: Reduced Circulating Transferrin
    treatment_effect: RESTORES
    description: >-
      Exogenous plasma supplies the deficient circulating carrier.
    evidence:
    - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
      reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine,
        hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig
        ervaring).
      explanation: >-
        The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while
        noting limited apotransferrin experience. Its evidence base consists of small case reports.
  - target: Reduced Erythroid Iron Delivery
    treatment_effect: RESTORES
    description: >-
      Replacement supports erythroid iron delivery and hemoglobin production.
    evidence:
    - reference: PMID:28824244
      reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        The patient has responded to treatment regimen of monthly infusions of fresh frozen plasma (FFP),
        with an increase of reticulocyte count to 6% at 2 weeks, Hb rise to 12.4 mg/dL at 1 month and
        decline of serum ferritin to 903 µg/L after 12 months.
      explanation: >-
        Response was documented in the boy only; the girl was lost to follow-up. The quoted hemoglobin
        unit is the source’s typographical error and is not used as a dose or treatment target.
- name: Purified apotransferrin replacement
  description: >-
    Purified transferrin or apotransferrin is an alternative replacement approach described in small historical
    reports. Availability, optimal dosing and comparative long-term outcomes remain limited. Normalization
    of hemoglobin does not guarantee removal of accumulated organ iron.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
    reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine,
      hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig
      ervaring).
    explanation: >-
      The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while noting
      limited apotransferrin experience. Its evidence base consists of small case reports.
  - reference: PMID:8317485
    reference_title: 'Studies on familial hypotransferrinemia: unique clinical course and molecular pathology.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The long-term clinical, laboratory, and developmental observations revealed that after 5 years of
      apo-TF supplementary therapy the patient's anemia gradually disappeared, and he started to grow again
      without further therapy.
    explanation: >-
      Historical family-specific longitudinal observation; residual transferrin increased, so lasting benefit
      cannot be assigned solely to a short-term pharmacological effect.
  - *id005
  - &id013
    reference: clinicaltrials:NCT01797055
    reference_title: Dose Escalating Study to Evaluate Pharmacokinetics, Efficacy and Safety of Apotransferrin in Atransferrinemia Patients
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: >-
      The objective of this study is to investigate the pharmacokinetics, efficacy and safety of Apotransferrin
      replacement therapy in atransferrinemia patients.
    explanation: >-
      Registry study objective, not a reported efficacy or safety result.
  target_mechanisms:
  - target: Reduced Circulating Transferrin
    treatment_effect: RESTORES
    description: >-
      Replacement provides functional iron-binding protein.
    evidence:
    - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
      reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        De expert groep is van mening dat een pati&euml;nt bij voorkeur moet worden behandeld met transferrine,
        hiervoor zijn twee mogelijkheden: plasma of apo-transferrine (met apo- transferrine is nog weinig
        ervaring).
      explanation: >-
        The 2014 Dutch guideline recommends transferrin replacement via plasma or apotransferrin, while
        noting limited apotransferrin experience. Its evidence base consists of small case reports.
- name: Iron chelation
  description: >-
    Chelation is considered for documented iron overload according to organ burden and clinical status. Desferrioxamine
    followed by deferiprone was used in the recent pediatric report, but its planned follow-up MRI result
    is not supplied. Drug selection, toxicity surveillance and efficacy estimates cannot be inferred from
    that single exposure.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: desferrioxamine B
      term:
        id: CHEBI:4356
        label: desferrioxamine B
    - preferred_term: deferiprone
      term:
        id: CHEBI:68554
        label: deferiprone
  evidence:
  - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
    reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine en
      klachten. Als alternatief kan chelatie therapie worden gegeven.
    explanation: >-
      The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation as
      an alternative; it does not endorse routine blood removal despite severe anemia.
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The patient was initiated on iron chelation therapy with injectable desferrioxamine, followed by
      oral deferiprone. A repeat MRI was planned after six months to evaluate treatment efficacy and guide
      further management.
    explanation: >-
      Observed treatment exposure without reported follow-up efficacy in this case.
  - &id006
    reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      In case of systemic iron loading, phlebotomies are recommended. If phlebotomies are not tolerated
      because of decreasing Hb, chelation therapy is rec ommended.
    explanation: >-
      The published guideline explicitly makes chelation an alternative when falling hemoglobin limits
      phlebotomy; the word break is preserved from the generated PDF.
  target_mechanisms:
  - target: Parenchymal Iron Accumulation
    treatment_effect: INHIBITS
    description: >-
      Chelation aims to lower body and organ iron burden; the cited pediatric case documents use, not a
      measured response.
    evidence:
    - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
      reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine
        en klachten. Als alternatief kan chelatie therapie worden gegeven.
      explanation: >-
        The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation
        as an alternative; it does not endorse routine blood removal despite severe anemia.
    - reference: PMID:41220266
      reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        The patient was initiated on iron chelation therapy with injectable desferrioxamine, followed
        by oral deferiprone. A repeat MRI was planned after six months to evaluate treatment efficacy
        and guide further management.
      explanation: >-
        Observed treatment exposure without reported follow-up efficacy in this case.
- name: Therapeutic phlebotomy in selected patients
  description: >-
    Blood removal can lower iron burden when erythropoiesis and hemoglobin permit. The guideline advises
    adjustment to hemoglobin, ferritin and symptoms. One nonanemic adult sister tolerated monthly phlebotomy
    without transferrin replacement; this must not be generalized to severely anemic children.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Phlebotomy
    term:
      id: NCIT:C28221
      label: Phlebotomy
  evidence:
  - reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
    reference_title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      In geval van ijzerstapeling, adviseert de werkgroep aderlatingen op geleide van Hb, ferritine en
      klachten. Als alternatief kan chelatie therapie worden gegeven.
    explanation: >-
      The guideline conditions phlebotomy on hemoglobin, ferritin and symptoms and offers chelation as
      an alternative; it does not endorse routine blood removal despite severe anemia.
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Bloodletting (300cc month ly w ithout plasma or purified transferrin supplementation) was well tolerated
      and efficient ; after one year of treatment, the ferritin level was 115µg/L without anemia.
    explanation: >-
      Observed outcome in the nonanemic adult sister, not evidence of tolerability in patients with profound
      anemia.
  - *id006
  target_mechanisms:
  - target: Parenchymal Iron Accumulation
    treatment_effect: INHIBITS
    description: >-
      Blood removal lowers stored iron; the cited adult response was measured by ferritin, without a paired
      follow-up tissue-iron result.
    evidence:
    - reference: PMID:40112917
      reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        Bloodletting (300cc month ly w ithout plasma or purified transferrin supplementation) was well
        tolerated and efficient ; after one year of treatment, the ferritin level was 115µg/L without
        anemia.
      explanation: >-
        Observed outcome in the nonanemic adult sister, not evidence of tolerability in patients with
        profound anemia.
      directness: INDIRECT
- name: Individualized iron supplementation with transferrin replacement
  description: >-
    Iron alone does not correct carrier deficiency and can aggravate loading. A Turkish patient received
    oral iron with regular plasma and later an individualized change in duration to maintain hemoglobin.
    This uncontrolled, overlapping follow-up does not support routine supplementation in iron-overloaded
    patients or establish superiority over adequate transferrin replacement.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Blood transfusions or treatments with iron are ineffective and aggravate iron overload.
    explanation: >-
      General caution about treatment that does not correct transferrin deficiency; paired iron-plus-replacement
      is considered separately.
  - reference: PMID:34792309
    reference_title: 'Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade: A Dynamic Approach to Maintaining Hematological Stability.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      In conclusion, our experience of almost 14 years reveals that fresh frozen plasma plus iron therapy
      may be advantageous over standard fresh frozen plasma transfusion. With this therapy, the stable
      Hb control seen in this case in the first decade was re-achieved in the second decade.
    explanation: >-
      Single-patient experience without a randomized comparator; proposed superiority is not established.
  target_mechanisms:
  - target: Reduced Erythroid Iron Delivery
    treatment_effect: MODULATES
    description: >-
      Iron supplied alongside replacement may alter marrow availability in an individually monitored patient;
      its independent effect is unresolved.
    evidence:
    - reference: PMID:34792309
      reference_title: 'Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade: A Dynamic Approach to Maintaining Hematological Stability.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: >-
        In conclusion, our experience of almost 14 years reveals that fresh frozen plasma plus iron therapy
        may be advantageous over standard fresh frozen plasma transfusion. With this therapy, the stable
        Hb control seen in this case in the first decade was re-achieved in the second decade.
      explanation: >-
        Single-patient experience without a randomized comparator; proposed superiority is not established.
- name: Cardiac and endocrine complication management
  description: >-
    Cardiac failure and diabetes require specialist management alongside iron-directed treatment. The review
    discusses conventional heart-failure therapy but explicitly lacks atransferrinemia-specific evidence
    for newer adult HFrEF agents; their adult efficacy is not a pediatric disease-specific recommendation.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      A 13-year-old girl born of second-degree consanguinity presented with heart failure, severe anemia,
      and diabetes mellitus. Her clinical course included heart failure at six months, diabetes at age
      seven, and progressive LV systolic dysfunction. Iron studies revealed low TIBC, elevated ferritin,
      low transferrin saturation, and undetectable transferrin levels (<75 mg/dL). Echocardiography showed
      severe biventricular systolic dysfunction. There was an incidentally detected 4 mm PDA (Fig. 4).
      As the age advanced, heart failure worsened disproportionately. Cardiac MRI confirmed myocardial
      iron overload, and genetic testing identified a novel mutation, confirming the diagnosis. This highlights
      the importance of early recognition and genetic analysis in hereditary atransferrinemia.
    explanation: >-
      Primary clinical case embedded in a review. Its intronic TF variant is later classified as a VUS,
      so the phenotype is clinically consistent but the allele is not functionally confirmed.
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Although ARNIs and SGLT2 inhibitors have not been specifically studied in iron overload cardiomyopathies
      or atransferrinemia, they have shown efficacy in heart failure with reduced ejection fraction (HFrEF)
      in adults. The treatment should be tailored according to the clinical presentation of the patient
      [25].
    explanation: >-
      The review explicitly distinguishes adult HFrEF evidence from disease-specific evidence.
- name: Longitudinal iron and organ surveillance
  description: >-
    Follow hemoglobin, transferrin, ferritin and symptoms, with tissue-iron imaging and organ assessment
    where indicated. Serum ferritin alone does not identify the distribution of cardiac versus hepatic iron.
    Growth and treatment requirements may change over time.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Our patients need to be in long-term follow-up to monitor the effectiveness of therapy and manage
      iron overload.
    explanation: >-
      Authors recommend ongoing monitoring; only one of their two patients remained in follow-up.
  - reference: PMID:41220266
    reference_title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Cardiac MRI T2* remains a unique and reliable modality for diagnosing and quantifying cardiac iron
      overload and monitoring therapy in iron overload cardiomyopathies, including atransferrinemia.
    explanation: >-
      Review supports the imaging role, without a controlled mortality benefit.
  - reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    reference_title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Iron status should be monitored in patients with hypotransferrinemia due to a TF defect in order
      to detect toxic iron loading early.
    explanation: >-
      Published disease-specific monitoring recommendation, not an outcome comparison.
- name: Genetic counseling and family evaluation
  description: >-
    Explain recessive inheritance, variant uncertainty and the variable anemia/iron-overload phenotype. Offer
    targeted familial testing and iron studies when a relevant variant is established; do not treat every
    rare variant as pathogenic.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Diagnosis is confirmed by molecular genetic testing for mutation in the TF gene. Genetic counseling
      is available.
    explanation: >-
      Clinical diagnostic and counseling recommendation.
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Family screening revealed her sister (52yo) was homozygous for the same TF variant.
    explanation: >-
      Family investigation identified a nonanemic relative with significant iron overload.
diagnosis:
- name: Integrated iron and hematologic assessment
  description: >-
    Measure transferrin directly alongside hemoglobin, indices, serum iron, TIBC and ferritin. Severe childhood
    iron-refractory microcytosis is a classic trigger, but unexplained parenchymal iron overload with very
    low transferrin also warrants evaluation in adults without anemia. Calculated transferrin saturation
    is variable and can exceed 100% with a very small denominator; no fixed low-saturation threshold is diagnostic.
  diagnosis_term:
    preferred_term: Laboratory Procedure
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  evidence:
  - *id007
  - *id008
  - *id001
- name: TF molecular testing and variant interpretation
  description: >-
    Sequence TF and evaluate segregation and variant class in the clinical context. A VUS does not by itself
    establish the molecular diagnosis or a splice defect; RNA or other appropriate functional analysis may
    be needed. Clinical reports without testing remain clinically diagnosed.
  diagnosis_term:
    preferred_term: Genetic Testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:28824244
    reference_title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Diagnosis is confirmed by molecular genetic testing for mutation in the TF gene.
    explanation: >-
      Clinical recommendation.
  - *id009
- name: Cardiac and hepatic iron assessment
  description: >-
    MRI-based tissue-iron assessment and cardiac functional imaging characterize burden and complications.
    Hepatic and myocardial iron may differ within one patient; iron quantification is not a direct assay
    of oxidative injury or proof of fibrosis.
  diagnosis_term:
    preferred_term: Magnetic Resonance Imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging
  evidence:
  - *id002
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Cardiac MRI findings were normal, without iron overload.
    explanation: >-
      The adult sister had liver iron overload but normal cardiac MRI, showing tissue-specific heterogeneity.
- name: Exclude acquired hypotransferrinemia
  description: >-
    Assess liver disease, inflammation, nutritional status and protein losses. A reversible adult acquired
    case recovered transferrin after treatment of enteropathy; age alone cannot exclude congenital disease
    because late-presenting homozygous TF cases are now documented.
  evidence:
  - reference: PMID:36627980
    reference_title: 'Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport?'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The most convincing argument was the subsequent normalization of serum Tf after the resolution of
      the acute episode.
    explanation: >-
      Recovery supported an acquired explanation in that patient; its other exclusion arguments should
      not be universalized.
  - *id001
animal_models:
- species: Mouse
  genotype: Trf hpx/hpx on a BALB/cJ background in the mechanistic study
  description: >-
    The spontaneous splice-donor allele produces severe transferrin deficiency, anemia and nonhematopoietic
    iron loading. The 2011 study compared replacement, washed wild-type red-cell transfusion and myeloablation
    followed by transferrin. Replacement improved hematologic and hepcidin readouts; withdrawal allowed recurrence.
    Suppression of erythropoiesis and restoration of transferrin make separable contributions. The study
    does not establish apoptosis of immature erythrocytes, a complete human signaling chain or universal
    clinical rescue.
  genes:
  - preferred_term: TF
    term:
      id: hgnc:11740
      label: TF
  evidence:
  - reference: PMID:10910930
    reference_title: The molecular defect in hypotransferrinemic mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      It results from a single point mutation, which alters an invariable nucleotide in the splice donor
      site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from the hpx allele.
    explanation: >-
      Defined spontaneous mouse splice defect; the accessible source is an abstract.
  - reference: PMID:20956801
    reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      By the third day of treatment, spleen masses had decreased and hematocrits had normalized; by the
      sixth day of treatment, hepcidin levels were elevated from baseline to levels similar to those observed
      in wild-type mice (data not shown). Six weeks after cessation of treatment, hematocrits, spleen masses,
      and hepcidin levels reverted to pretreatment or near-pretreatment levels (data not shown).
    explanation: >-
      Main-body report of rapid response and recurrence after withdrawal; the numerical data are not shown
      in the paper.
  - reference: PMID:20956801
    reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by approximately
      eighty-fold and seventeen-fold, respectively (Figure 6F).
    explanation: >-
      Transferrin stimulation after myeloablation supports an erythropoiesis-independent component. Different
      protein doses prevent a human-versus-mouse potency comparison.
  modeled_mechanisms:
  - target: Reduced Circulating Transferrin
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      The hpx splice allele reduces the normal circulating carrier.
    limitations: >-
      This postnatal mouse splice defect models severe deficiency, not every human missense allele or the
      nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and
      iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation.
      No specific human receptor or erythroid mediator is isolated.
    evidence:
    - reference: PMID:10910930
      reference_title: The molecular defect in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        It results from a single point mutation, which alters an invariable nucleotide in the splice
        donor site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from the
        hpx allele.
      explanation: >-
        Defined spontaneous mouse splice defect; the accessible source is an abstract.
    readouts:
    - name: Abnormal Trf splicing
      target: Reduced Circulating Transferrin
      direction: ALTERED
      interpretation: >-
        The hpx splice allele reduces the normal circulating carrier.
      evidence:
      - reference: PMID:10910930
        reference_title: The molecular defect in hypotransferrinemic mice.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: >-
          It results from a single point mutation, which alters an invariable nucleotide in the splice
          donor site after exon 16 of the Trf gene. No normal Trf messenger RNA (mRNA) is made from
          the hpx allele.
        explanation: >-
          Defined spontaneous mouse splice defect; the accessible source is an abstract.
  - target: Reduced Hemoglobin Synthesis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Replacement improves hematologic readouts of iron-restricted erythropoiesis.
    limitations: >-
      This postnatal mouse splice defect models severe deficiency, not every human missense allele or the
      nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and
      iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation.
      No specific human receptor or erythroid mediator is isolated.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        By the third day of treatment, spleen masses had decreased and hematocrits had normalized; by
        the sixth day of treatment, hepcidin levels were elevated from baseline to levels similar to
        those observed in wild-type mice (data not shown). Six weeks after cessation of treatment, hematocrits,
        spleen masses, and hepcidin levels reverted to pretreatment or near-pretreatment levels (data
        not shown).
      explanation: >-
        Main-body report of rapid response and recurrence after withdrawal; the numerical data are not
        shown in the paper.
    readouts:
    - name: Hematocrit response
      target: Reduced Hemoglobin Synthesis
      direction: ALTERED
      interpretation: >-
        Replacement improves hematologic readouts of iron-restricted erythropoiesis.
      evidence:
      - reference: PMID:20956801
        reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: >-
          By the third day of treatment, spleen masses had decreased and hematocrits had normalized;
          by the sixth day of treatment, hepcidin levels were elevated from baseline to levels similar
          to those observed in wild-type mice (data not shown). Six weeks after cessation of treatment,
          hematocrits, spleen masses, and hepcidin levels reverted to pretreatment or near-pretreatment
          levels (data not shown).
        explanation: >-
          Main-body report of rapid response and recurrence after withdrawal; the numerical data are
          not shown in the paper.
  - target: Reduced Transferrin-Dependent Hepcidin Stimulation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Transferrin stimulates hepatic hepcidin after myeloablation.
    limitations: >-
      This postnatal mouse splice defect models severe deficiency, not every human missense allele or the
      nonanemic adult spectrum. Early survival support, strain-dependent drug responses, myelotoxic and
      iron-chelating effects of doxorubicin, and different transferrin doses constrain causal interpretation.
      No specific human receptor or erythroid mediator is isolated.
    evidence:
    - reference: PMID:20956801
      reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by approximately
        eighty-fold and seventeen-fold, respectively (Figure 6F).
      explanation: >-
        Transferrin stimulation after myeloablation supports an erythropoiesis-independent component.
        Different protein doses prevent a human-versus-mouse potency comparison.
    readouts:
    - name: Hepatic hepcidin RNA after transferrin
      target: Reduced Transferrin-Dependent Hepcidin Stimulation
      direction: ALTERED
      interpretation: >-
        Transferrin stimulates hepatic hepcidin after myeloablation.
      evidence:
      - reference: PMID:20956801
        reference_title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: >-
          Hepcidin expression increased in mice treated with doxorubicin and human or murine Tf by
          approximately eighty-fold and seventeen-fold, respectively (Figure 6F).
        explanation: >-
          Transferrin stimulation after myeloablation supports an erythropoiesis-independent component.
          Different protein doses prevent a human-versus-mouse potency comparison.
- species: Zebrafish
  genotype: gavi transferrin-a splice alleles and transferrin-a morphants
  description: >-
    Two recessive gavi splice alleles predict truncated transferrin-a and produce hypochromic anemia with
    early lethality. Morpholino knockdown reproduced reduced hemoglobin and tissue-iron staining; transferrin-a
    cRNA partially restored them. TfR2 knockdown reduced hepcidin without anemia, whereas anemia induced
    outside the transferrin pathway did not lower basal embryonic hepcidin. The complete main body, methods
    and captions were reviewed; separate supplementary objects were not assessed.
  genes:
  - preferred_term: TF
    term:
      id: hgnc:11740
      label: TF
  evidence:
  - reference: PMID:19047682
    reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype and decreased
      somite and terminal gut iron staining, while coinjection of transferrin-a cRNA partially restored
      these defects.
    explanation: >-
      Embryonic perturbation and partial rescue of histochemical readouts.
  - &id012
    reference: PMID:19047682
    reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of hepcidin
      expression, however anemia, in the absence of a defect in the transferrin pathway, failed to impair
      hepcidin expression.
    explanation: >-
      Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2661867/
    reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos - PMC
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: >-
      both of which exhibit a recessive pattern of inheritance, hypochromic anemia at 48 hpf
    explanation: >-
      The complete primary Results section describes both gavi alleles; embryonic phenotype timing is not
      a human onset estimate.
  modeled_mechanisms:
  - target: Reduced Erythroid Iron Delivery
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Deficient embryos have reduced hemoglobin staining, improved by partial experimental rescue.
    limitations: >-
      Nonfeeding embryos were examined mainly at 48–72 hours after fertilization; reduced somite/proctodeal
      iron is not adult parenchymal overload. Histochemistry and hepcidin RNA do not directly measure transport
      flux or protein secretion. Rescue is partial and experimental, not a human treatment comparison.
      Human HFE circuitry is not established in this fish system.
    evidence:
    - reference: PMID:19047682
      reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype and
        decreased somite and terminal gut iron staining, while coinjection of transferrin-a cRNA partially
        restored these defects.
      explanation: >-
        Embryonic perturbation and partial rescue of histochemical readouts.
    readouts:
    - name: Hemoglobin histochemistry
      target: Reduced Erythroid Iron Delivery
      direction: DECREASED
      interpretation: >-
        Deficient embryos have reduced hemoglobin staining, improved by partial experimental rescue.
      evidence:
      - reference: PMID:19047682
        reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: >-
          Morpholino knockdown of transferrin-a in wild-type embryos reproduced the anemia phenotype
          and decreased somite and terminal gut iron staining, while coinjection of transferrin-a cRNA
          partially restored these defects.
        explanation: >-
          Embryonic perturbation and partial rescue of histochemical readouts.
  - target: Reduced Transferrin-Dependent Hepcidin Stimulation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Transferrin-a and TfR2 perturbations lower basal hepcidin RNA.
    limitations: >-
      Nonfeeding embryos were examined mainly at 48–72 hours after fertilization; reduced somite/proctodeal
      iron is not adult parenchymal overload. Histochemistry and hepcidin RNA do not directly measure transport
      flux or protein secretion. Rescue is partial and experimental, not a human treatment comparison.
      Human HFE circuitry is not established in this fish system.
    evidence:
    - reference: PMID:19047682
      reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: >-
        Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels of
        hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway, failed
        to impair hepcidin expression.
      explanation: >-
        Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin response.
    readouts:
    - name: Embryonic hepcidin expression
      target: Reduced Transferrin-Dependent Hepcidin Stimulation
      direction: DECREASED
      interpretation: >-
        Transferrin-a and TfR2 perturbations lower basal hepcidin RNA.
      evidence:
      - reference: PMID:19047682
        reference_title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        quote_role: PRIMARY_RESULT
        snippet: >-
          Embryos with transferrin-a or transferrin receptor 2 (TfR2) deficiency exhibited low levels
          of hepcidin expression, however anemia, in the absence of a defect in the transferrin pathway,
          failed to impair hepcidin expression.
        explanation: >-
          Embryonic transferrin-pathway dependence differs from the general mammalian anemia-hepcidin
          response.
review_notes: >-
  No disease-specific GeneReviews or StatPearls chapter was identified. The complete matching research and
  original references were assessed. Unsupported phenotype frequencies, complete penetrance, obligatory childhood
  anemia and uniformly low transferrin saturation were removed. The two-case 2017 abstract claims both children
  responded to FFP, but its body says the girl was lost to follow-up; only the boy has a documented response.
  The 2007, 2018 and 2022 Turkish reports overlap. The 2026 review embeds one case whose novel intronic TF
  deletion is explicitly a VUS despite earlier diagnostic wording. A 2025 adult family establishes mild or
  absent anemia with severe iron overload, without proving an alternative erythroid transport route. The research
  citation PMID10654962 concerns a different neonatal iron-overload syndrome and was not used as TF-disease
  evidence. PMID39081172 has no accessible abstract or full body after normal retrieval attempts; its title
  alone does not establish functional results. Full text was used wherever actually recovered, irrespective
  of cache content-type labels. The primary 2014 microcytic-anemia guideline (PMID:24665134) supplies disease-specific
  replacement, hemoglobin-guided phlebotomy/chelation and monitoring recommendations; it is not presented as
  new guidance. Skin iron deposition is mentioned there without a sufficiently precise phenotype binding and
  remains an uncoded source observation. NCT01797055 was recovered from the live registry and is represented
  as a design-only study with no posted results. Author-thesis retrieval for the unavailable 2024 functional
  study failed through the original repository and its alternate public domain; no findings were reconstructed
  from its title.
progression:
- phase: Variable childhood or adult presentation
  notes: >-
    Severe iron-refractory anemia and growth impairment commonly prompt childhood diagnosis. Adult-onset
    iron loading with mild or absent anemia is documented; therefore anemia onset, organ-failure sequence
    and untreated mortality cannot be assigned universal ages or frequencies.
  evidence:
  - reference: PMID:30420953
    reference_title: Inherited Disorders of Iron Overload.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      This leads to impaired erythropoiesis, microcytic hypochromic anemia, growth retardation and iron
      overload in parenchymal cells of the liver, heart and pancreas.
    explanation: >-
      Clinical review describes the classic phenotype; later familial observations establish that severe
      childhood anemia is not universal.
  - *id001
- phase: Treatment and organ burden over time
  notes: >-
    Replacement can improve hemoglobin, but dose or interval may need reassessment with growth. Ferritin,
    transferrin and tissue iron are distinct measurements, and established organ injury may persist. Long-term
    clinical series are small and often repeat the same patients.
  evidence:
  - reference: PMID:34792309
    reference_title: 'Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade: A Dynamic Approach to Maintaining Hematological Stability.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      However, at the start of the second decade, Hb and ferritin began to decline and the therapy was
      revised.
    explanation: >-
      Within-patient longitudinal change after the first decade of treatment; not proof of treatment failure
      in every patient.
biochemical:
- name: Urinary hepcidin response during plasma replacement
  notes: >-
    In one child, urinary hepcidin rose during intensified transferrin replacement and subsequently fell
    as infusions became less frequent. This is a dynamic research observation, not a universally absent hormone
    or a stand-alone diagnostic threshold.
  evidence:
  - *id010
- name: Non-transferrin-bound iron
  notes: >-
    The nonanemic adult sister had measurable excess NTBI. Assay-specific NTBI is distinct from serum iron
    and calculated transferrin saturation.
  evidence:
  - *id008
- name: Abnormal circulating transferrin molecular forms
  notes: >-
    In the Italian child, serum protein analysis found approximately 80-kDa and 50-kDa transferrin forms.
    The authors considered degradation or an altered allele product as alternatives; the accessible abstract
    does not resolve the origin of the smaller form.
  evidence:
  - reference: PMID:11920219
    reference_title: Biochemical and genetic defects underlying human congenital hypotransferrinemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Protein analyses indicate that the proband serum contains two transferrin forms: one of 80 kD analogous
      to the normal one, and a smaller one of 50 kD, which may arise from a specific degradation or be
      the gene product of a modified allele.
    explanation: >-
      Observed serum protein forms with explicitly unresolved origin of the smaller species.
histopathology:
- name: Myocardial iron deposition and fibrosis
  description: >-
    The explanted heart of the adult index patient showed widespread cardiomyocyte iron and fibrosis. The
    patient died of primary graft failure; this does not establish that all iron cardiomyopathy is irreversible
    or that graft iron deposition caused death.
  evidence:
  - reference: PMID:40112917
    reference_title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Pathological examination of the explant ed heart revealed widespread iron overload and fibrosis in
      the cardiomyocytes.
    explanation: >-
      Primary pathological finding in one adult with homozygous TF p.Glu370Lys.
discussions:
- discussion_id: gap_variable_erythropoiesis
  kind: KNOWLEDGE_GAP
  prompt: What permits preserved erythropoiesis in some patients with profound transferrin deficiency?
  rationale: >-
    Adult sisters and a historical family have mild or absent anemia at very low transferrin levels. Residual
    carrier availability, other inherited factors and alternative uptake routes are plausible but not resolved.
    The acquired enteropathy case had trace transferrin and transfusion exposure. None of these clinical
    observations proves a specific compensatory transporter or a universal safe transferrin threshold.
  attaches_to:
  - pathophysiology#Reduced Erythroid Iron Delivery
  evidence:
  - *id001
  - reference: PMID:36627980
    reference_title: 'Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport?'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The mildness of the clinical and haematological manifestations raises questions on possible compensatory
      mechanisms for erythroblastic iron supply, which remain to be investigated.
    explanation: >-
      The acquired-case authors explicitly frame compensation as an unresolved question.
- discussion_id: gap_human_hepcidin_signals
  kind: KNOWLEDGE_GAP
  prompt: How do transferrin-dependent sensing and erythroid demand combine to regulate human hepcidin?
  rationale: >-
    The mouse perturbations support separable contributions but do not isolate the complete molecular pathway.
    Human urinary-hepcidin observations are sparse and treatment-linked; embryonic fish anemia does not reproduce
    the postnatal mammalian suppression pattern. GDF15/TWSG1 transcripts, proposed ERFE signaling and receptor
    models should not be promoted into proven necessary human intermediates.
  attaches_to:
  - pathophysiology#Reduced Transferrin-Dependent Hepcidin Stimulation
  - pathophysiology#Increased Erythropoietic Drive
  evidence:
  - *id011
  - *id010
  - *id012
- discussion_id: gap_intronic_variant_function
  kind: KNOWLEDGE_GAP
  prompt: Does the newly reported intronic TF deletion alter splicing or protein expression?
  rationale: >-
    The 2026 review describes a homozygous intronic deletion, a heterozygous mother and absent population
    observations, but explicitly classifies the allele as VUS. A compatible severe iron-loading phenotype
    is not a functional splice assay or sufficient evidence to reclassify the allele.
  attaches_to:
  - pathophysiology#Biallelic TF Defect
  evidence:
  - *id009
references:
- reference: PMID:10910930
  title: The molecular defect in hypotransferrinemic mice.
- reference: PMID:11110675
  title: Molecular characterization of a case of atransferrinemia.
- reference: PMID:11920219
  title: Biochemical and genetic defects underlying human congenital hypotransferrinemia.
- reference: PMID:17768112
  title: Effects of plasma transfusion on hepcidin production in human congenital hypotransferrinemia.
- reference: PMID:18097132
  title: A new case of human atransferrinemia with a previously undescribed mutation in the transferrin gene.
- reference: PMID:19047682
  title: Transferrin-a modulates hepcidin expression in zebrafish embryos.
- reference: PMID:19579082
  title: Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
- reference: PMID:20956801
  title: Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
- reference: PMID:24665134
  title: Practice guidelines for the diagnosis and management of microcytic anemias due to genetic disorders of iron metabolism or heme synthesis.
- reference: PMID:25486930
  title: Hereditary hypotransferrinemia can lead to elevated transferrin saturation and, when associated to HFE or HAMP mutations, to iron overload.
- reference: PMID:28824244
  title: 'Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.'
- reference: PMID:28895280
  title: 'Addition of oral iron to plasma transfusion in human congenital hypotransferrinemia: A 10-year observational follow-up with the effects on hematological parameters and growth.'
- reference: PMID:30420953
  title: Inherited Disorders of Iron Overload.
- reference: PMID:34792309
  title: 'Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade: A Dynamic Approach to Maintaining Hematological Stability.'
- reference: PMID:36627980
  title: 'Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport?'
- reference: PMID:40112917
  title: Hypotransferrinemia leading to fatal hemochromatosis without anemia.
- reference: PMID:41220266
  title: 'Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.'
- reference: PMID:8317485
  title: 'Studies on familial hypotransferrinemia: unique clinical course and molecular pathology.'
- reference: clinicaltrials:NCT01797055
  title: Dose Escalating Study to Evaluate Pharmacokinetics, Efficacy and Safety of Apotransferrin in Atransferrinemia Patients
- reference: url:https://clinicaltrials.gov/api/v2/studies/NCT01797055
  title: https://clinicaltrials.gov/api/v2/studies/NCT01797055
- reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2661867/
  title: Transferrin-a modulates hepcidin expression in zebrafish embryos - PMC
- reference: url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
  title: https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
- reference: url:https://richtlijnendatabase.nl/richtlijn/anemie_door_aangeboren_stoornissen/atransferrinemie_anemie_door_tf/behandeling_atransferrinemie_anemie.html
  title: Behandeling atransferrinemie (anemie) - Richtlijn - Richtlijnendatabase
clinical_trials:
- name: NCT01797055
  phase: PHASE_II
  status: ACTIVE_NOT_RECRUITING
  description: >-
    This phase II open-label, single-group study evaluates intravenous human apotransferrin replacement.
    The official record updated September 16, 2026 lists five actual participants, active-not-recruiting
    status and estimated completion in January 2028. Outcomes include hemoglobin, transferrin pharmacokinetics,
    organ iron and adverse reactions. No results are posted; the registry does not establish clinical benefit
    or the optimal regimen. Its transferrin below 40 mg/dL eligibility threshold is a study criterion, not
    a universal diagnostic cutoff.
  target_phenotypes:
  - preferred_term: Hypochromic microcytic anemia
    term:
      id: HP:0004840
      label: Hypochromic microcytic anemia
  - preferred_term: Atransferrinemia
    term:
      id: HP:0012239
      label: Atransferrinemia
  evidence:
  - *id013
  - reference: url:https://clinicaltrials.gov/api/v2/studies/NCT01797055
    reference_title: https://clinicaltrials.gov/api/v2/studies/NCT01797055
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: >-
      serum transferrin levels measured on several time points before and after infusion
    explanation: >-
      Prespecified pharmacokinetic outcome in the complete official registry record, not a posted result.
📚

References & Deep Research

References

23
PMID:10910930
The molecular defect in hypotransferrinemic mice.
No top-level findings curated for this source.
PMID:11110675
Molecular characterization of a case of atransferrinemia.
No top-level findings curated for this source.
PMID:11920219
Biochemical and genetic defects underlying human congenital hypotransferrinemia.
No top-level findings curated for this source.
PMID:17768112
Effects of plasma transfusion on hepcidin production in human congenital hypotransferrinemia.
No top-level findings curated for this source.
PMID:18097132
A new case of human atransferrinemia with a previously undescribed mutation in the transferrin gene.
No top-level findings curated for this source.
PMID:19047682
Transferrin-a modulates hepcidin expression in zebrafish embryos.
No top-level findings curated for this source.
PMID:19579082
Severe hypochromic microcytic anemia in a patient with congenital atransferrinemia.
No top-level findings curated for this source.
PMID:20956801
Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice.
No top-level findings curated for this source.
PMID:24665134
Practice guidelines for the diagnosis and management of microcytic anemias due to genetic disorders of iron metabolism or heme synthesis.
No top-level findings curated for this source.
PMID:25486930
Hereditary hypotransferrinemia can lead to elevated transferrin saturation and, when associated to HFE or HAMP mutations, to iron overload.
No top-level findings curated for this source.
PMID:28824244
Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases.
No top-level findings curated for this source.
PMID:28895280
Addition of oral iron to plasma transfusion in human congenital hypotransferrinemia: A 10-year observational follow-up with the effects on hematological parameters and growth.
No top-level findings curated for this source.
PMID:30420953
Inherited Disorders of Iron Overload.
No top-level findings curated for this source.
PMID:34792309
Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade: A Dynamic Approach to Maintaining Hematological Stability.
No top-level findings curated for this source.
PMID:36627980
Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport?
No top-level findings curated for this source.
PMID:40112917
Hypotransferrinemia leading to fatal hemochromatosis without anemia.
No top-level findings curated for this source.
PMID:41220266
Revisiting Congenital Atransferrinemia: A Rare but Treatable Cause of Pediatric Heart Failure.
No top-level findings curated for this source.
PMID:8317485
Studies on familial hypotransferrinemia: unique clinical course and molecular pathology.
No top-level findings curated for this source.
clinicaltrials:NCT01797055
Dose Escalating Study to Evaluate Pharmacokinetics, Efficacy and Safety of Apotransferrin in Atransferrinemia Patients
No top-level findings curated for this source.
url:https://clinicaltrials.gov/api/v2/studies/NCT01797055
https://clinicaltrials.gov/api/v2/studies/NCT01797055
No top-level findings curated for this source.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2661867/
Transferrin-a modulates hepcidin expression in zebrafish embryos - PMC
No top-level findings curated for this source.
url:https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
https://richtlijnendatabase.nl/gerelateerde_documenten/file/5656/1/Donker%20Guidelines%20anemia%20Blood%202014.pdf
No top-level findings curated for this source.
No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Review Atransferrinemia mechanisms, clinical spectrum and care · 2026-09-21T12:23:10Z · View source

Reviewed the complete matching deep-research report, citation inventory, all originally cited abstracts and actual cached full bodies, and newly recovered primary and guideline sources. Rebuilt 14 atomic mechanisms separating transferrin-dependent erythroid iron delivery from the independently supported hepcidin-regulatory contribution, then established iron-export, NTBI and organ-injury processes. Preserved model-species, neonatal survival support, transcript-versus-peptide, experimental rescue and unresolved receptor/erythroid-mediator limits. Independent full-source and integrated care audits were incorporated. Expanded to 27 supported phenotypes, four diagnostic approaches, eight care records, two animal models, biochemical/histopathology findings and three explicit knowledge gaps. Removed unsupported frequency/penetrance assignments and universal childhood anemia, transferrin threshold and low-saturation claims. Added the nonanemic adult iron-overload spectrum, selected phlebotomy response, guideline-supported replacement and hemoglobin-guided chelation, surveillance and family evaluation. Distinguished acquired enteropathy-associated deficiency from congenital TF disease. Added the live phase II NCT01797055 design and actual enrollment without inferring unpublished efficacy. Recorded source-internal conflicts and availability limits: only the boy in the 2017 two-case report has documented treatment follow-up; Turkish reports overlap; the 2026 intronic allele remains a VUS; adult E370K classification is attributed to the authors. PMID10654962 is a different neonatal syndrome and was excluded. The unavailable 2024 functional paper supplies no reconstructed findings. No disease-specific GeneReviews or StatPearls chapter was identified. Full bodies were actually read where recovered, including canonical fish full text, the mouse study, current adult/cardiac cases and the disease-applicable 2014 guideline sections. Generated caches were obtained only through fetch-reference; the frozen dataset-accession blob was not accessed. Authoritative validation passes schema, live ontology labels and all 166 evidence snippets. Whole-KB node-class verification resolves all 2189 examples; remaining repository guards and formatting are checked before publication. The review records source provenance, directness, exact excerpts, current reference titles and precise clinical/experimental scope.

Create: Atransferrinemia · 2026-08-08T14:50:23Z · View source

Created a greenfield entry for congenital atransferrinemia MONDO:0008846, causal gene TF hgnc:11740, OMIM 209300, autosomal recessive. Modeled the dual pathomechanism: transferrin deficiency to impaired iron delivery to erythroid precursors to microcytic hypochromic anemia, and in parallel non-transferrin-bound iron accumulation to parenchymal iron overload and hemosiderosis, connected with downstream causal edges into a single pathograph joined to phenotypes and to both treatments via target_mechanisms. Added inheritance with penetrance COMPLETE and expressivity VARIABLE, a variant summary p.Ala477Pro p.Asp77Asn p.Cys137Tyr, prevalence ULTRA_RARE CASES_IN_LITERATURE, 12 phenotypes, treatments apotransferrin/plasma replacement with iron-supplementation contraindication caveat and iron chelation, plus hpx mouse and zebrafish gavi animal models. Deep research provider claude_code, the only available provider since no external API keys are set. GeneReviews search returned no article so the GR baseline is N/A. Validation: just validate passes schema and terms, 22/22 evidence snippets verified against cached references, and just validate-disorders CI-equivalent batched sweep passes.

Claude Code ▸
Atransferrinemia (Congenital Hypotransferrinemia): Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 25 citations 2026-08-08T14:30:56.134219

Atransferrinemia (Congenital Hypotransferrinemia): Comprehensive Research Report

1. Disease Information

Overview. Atransferrinemia (also called congenital atransferrinemia, hereditary hypotransferrinemia, or familial hypotransferrinemia) is an extremely rare autosomal recessive metal-metabolism disorder caused by absent or severely reduced synthesis of transferrin, the principal plasma iron-transport glycoprotein. The disorder produces a paradoxical dual phenotype: severe microcytic, hypochromic anemia due to failure to deliver iron to erythroid precursors, together with progressive systemic (secondary) iron overload/hemosiderosis because absorbed dietary iron cannot be carried in a regulated, transferrin-bound form and instead accumulates as non-transferrin-bound iron (NTBI) in parenchymal tissues. It was first described by Heilmeyer et al. in 1961 (PMID:13906009) and remains one of the rarest inherited disorders of iron metabolism, with only ~16–20 genetically or clinically documented cases from ~14–16 families reported to date.

Key identifiers: - OMIM: #209300 (Atransferrinemia) — phenotype entry; 190000 — TF (Transferrin), the causal gene - Orphanet: ORPHA:1195 (Congenital atransferrinemia) - Gene: TF; HGNC:11740; chromosome 3q22.1 (some sources cite 3q21); 24 exons - Mondo Disease Ontology: integrates the OMIM/Orphanet records above (Mondo unifies OMIM:209300 and ORPHA:1195 into a single congenital-atransferrinemia disease concept) - MeSH/GTR: listed as "Atransferrinemia," concept C0521802 in NCBI's Genetic Testing Registry - ICD-10-CM: falls under E83.19 (Disorders of iron metabolism, other) — no dedicated code exists - Synonyms:* Congenital hypotransferrinemia; hereditary hypotransferrinemia; familial idiopathic hypotransferrinemia; transferrin deficiency

Source of information. Because the condition has been reported in fewer than 20 kindreds worldwide, essentially all available data derive from aggregated case reports and case series (individual-patient-level literature) rather than large disease registries or EHR-based cohorts — there is no population-level epidemiological database for this disease.

2. Etiology

Disease causal factors. Atransferrinemia is a monogenic, purely genetic disorder — there is no known infectious or primarily environmental cause of the congenital form. It results from homozygous or compound heterozygous loss-of-function mutations in the TF gene (OMIM *190000), which encodes the 679-amino-acid transferrin glycoprotein synthesized predominantly in hepatocytes. Loss of functional transferrin protein removes the principal iron chaperone from plasma, producing the combined anemia/iron-overload phenotype (OMIM #209300; PMID:11110675, PMID:15466165, PMID:18097132).

Genetic risk factors. - Causal variants (biallelic, TF gene): - c.[10bp del + 9bp dup ins] / c.1429G>C (p.Ala477Pro) — compound heterozygous, first reported U.S. case (PMID:11110675) - c.229G>A (p.Asp77Asn, D77N) — homozygous, third reported case (PMID:15466165) - c.410G>A (p.Cys137Tyr) — homozygous, first Turkish case, 11th reported patient (PMID:18097132) - c.1765C>T (p.Pro589Ser) — listed pathogenic in ClinVar for Atransferrinemia - c.-117G>A (5′ regulatory region variant) — reported in ClinVar associated with Atransferrinemia - More than 30 TF structural polymorphisms exist in the general population (the common TF C, especially TF C1, variant), but these are population variants distinct from the rare disease-causing null/hypomorphic alleles. - Susceptibility/modifier genes: none well established; disease severity appears to correlate with residual transferrin synthesis (complete absence vs. detectable low levels) rather than with variation at a second locus. - Consanguinity: several reported kindreds (e.g., the Turkish and other homozygous cases) involve consanguineous parents, consistent with autosomal recessive inheritance and founder-type homozygosity in small/isolated populations.

Environmental risk factors. Not applicable to the congenital form (purely genetic). However, an acquired ("secondary") atransferrinemia phenocopy can occur in adults from severe chronic undernutrition, systemic inflammation, protein-losing enteropathy, and liver failure, which suppress hepatic transferrin synthesis or increase its loss/consumption (PMC9807235). This acquired form is reversible with correction of the underlying nutritional/inflammatory/hepatic disease and — notably — a case report found that even with undetectable serum transferrin, a patient maintained near-normal hemoglobin, suggesting compensatory non-transferrin iron-delivery pathways can partially substitute in adults (see Mechanism section).

Protective factors. None specific to the germline disease are described in the literature; heterozygous (carrier) TF mutation carriers are asymptomatic, indicating that a single functional TF allele is sufficient for normal iron transport and provides protection against clinical disease.

Gene-environment interactions. No formal GxE data exist for congenital atransferrinemia given its rarity. The clearest interaction in the literature is disease-modifying: iron supplementation is contraindicated in congenital atransferrinemia because it does not correct the anemia (erythroid precursors cannot use free/NTBI iron efficiently for hemoglobin synthesis) and instead worsens secondary hemosiderosis — i.e., a therapeutic environmental exposure (dietary/parenteral iron) interacts adversely with the genetic lesion.

3. Phenotypes

Onset is typically in infancy to early childhood (some case series document presentation from birth to ~7–20 years, with most patients recognized before age 10). The clinical picture combines anemia-related symptoms with iron-overload-related organ dysfunction.

Phenotype Type HPO suggestion Frequency/Notes
Pallor Sign HP:0000980 (Pallor) Nearly universal presenting sign
Fatigue/lethargy Symptom HP:0012378 (Fatigue) Common presenting complaint
Failure to thrive / growth retardation Sign HP:0001508 (Failure to thrive) / HP:0001510 (Growth delay) Frequently reported
Microcytic anemia Lab abnormality HP:0001935 (Microcytic anemia) Defining feature; Hb as low as 5–6 g/dL reported
Hypochromic anemia Lab abnormality HP:0001931 (Hypochromic microcytic anemia — combined term) Co-occurs with microcytosis
Elevated serum ferritin Lab abnormality HP:0003281 (Elevated serum ferritin) Markedly elevated (e.g., 1413–2072 µg/L in one case series vs. normal 45–160) despite low serum iron in some reports, or elevated serum iron/transferrin saturation in others depending on tissue iron redistribution
Low/absent serum transferrin Lab abnormality (suggest verifying exact HPO term, e.g., "Decreased circulating transferrin concentration") Diagnostic hallmark; typically <35 mg/dL (severely reduced total iron-binding capacity)
Elevated transferrin saturation Lab abnormality HP:0032120 (Increased transferrin saturation) — verify Despite low/absent transferrin, % saturation is paradoxically elevated because the small pool present is fully iron-loaded
Hepatomegaly Sign HP:0002240 (Hepatomegaly) Common
Hepatic fibrosis/cirrhosis Complication HP:0001395 (Hepatic fibrosis) / HP:0001394 (Cirrhosis) Late complication of iron overload
Splenomegaly Sign HP:0001744 (Splenomegaly) Reported in some cases
Cardiomyopathy / heart failure Complication HP:0001638 (Cardiomyopathy) From cardiac iron deposition; can be fatal if untreated
Tachycardia / systolic ejection murmur Sign HP:0001649 (Tachycardia) / HP:0031650 (Systolic murmur) Attributed to chronic anemia (high-output state)
Recurrent infections Symptom HP:0002719 (Recurrent infections) Reported, possibly related to iron's effect on immune function
Anorexia / irritability Symptom HP:0002039 (Anorexia) / HP:0000737 (Irritability) Infantile presentation
Arthritis / joint involvement Sign HP:0001369 (Arthritis) Reported in a subset (iron-related arthropathy, akin to hemochromatotic arthropathy)
Hypothyroidism Complication HP:0000821 (Hypothyroidism) Endocrine iron-overload complication
Diabetes mellitus Complication HP:0000819 (Diabetes mellitus) Endocrine (pancreatic) iron-overload complication
Pancreatic iron deposition Sign (suggest UBERON/GO annotation rather than HPO) Iron accumulates preferentially in liver, heart, pancreas, thyroid, kidney
Hypospadias Congenital anomaly HP:0000047 (Hypospadias) Reported in one case, hypothesized secondary to fetal hypoxia from severe anemia rather than a direct TF effect
Intrauterine growth retardation, lactic acidosis, aminoaciduria (severe neonatal form) Sign cluster HP:0001511 / HP:0003128 / HP:0003355 Described in a severe neonatal presentation treated with apotransferrin/exchange transfusion (PMID:10654962); both infants ultimately died at 8–10 weeks

Severity/progression: Variable but generally progressive if untreated — from mild anemia recognized incidentally to life-threatening cardiac and hepatic iron deposition. Disease course is chronic/lifelong, punctuated by episodes requiring transfusion or plasma/transferrin infusion.

Quality of life impact: Chronic transfusion dependence, recurrent infusion visits, growth impairment, and risk of endocrine and cardiac complications substantially affect pediatric development and long-term quality of life; no disease-specific QOL instrument data were identified in the literature (consistent with its ultra-rarity).

4. Genetic/Molecular Information

Causal gene: TF (Transferrin), OMIM *190000, HGNC:11740, chromosome 3q22.1 (GRCh38: 3:133,661,998–133,796,641), 24 exons, encoding a bilobed 679-amino-acid iron-binding glycoprotein with two homologous iron-binding domains (N-lobe and C-lobe), each coordinating one Fe³⁺ ion together with a synergistic carbonate anion.

Pathogenic variants identified in confirmed atransferrinemia cases: | Variant (cDNA/protein) | Zygosity | Location | Case | Reference | |---|---|---|---|---| | 10-bp deletion + 9-bp duplicated-sequence insertion / c.1429G>C (p.Ala477Pro) | Compound heterozygous | — | First U.S. case | Beutler et al. 2000, Blood 96:4071–4074, PMID:11110675 | | c.229G>A (p.Asp77Asn, D77N), exon 3 | Homozygous | Exon 3 | Third reported case (parents/sibling heterozygous carriers) | Knisely, Gelbart, Beutler 2004, Blood 104:2607, PMID:15466165 | | c.410G>A (p.Cys137Tyr), exon 4 | Homozygous | Exon 4 | First Turkish case, 11th reported patient | PMID:18097132 | | c.1765C>T (p.Pro589Ser) | — | — | Listed in ClinVar under "Atransferrinemia" | ClinVar RCV000376325 | | c.-117G>A | — | 5′ regulatory | Listed in ClinVar under "Atransferrinemia" | ClinVar RCV000338348 |

Variant classification: Per ACMG/AMP framework as reflected in ClinVar, the confirmed causal alleles above are classified Pathogenic/Likely pathogenic for Atransferrinemia; numerous additional TF missense variants in ClinVar/dbSNP are classified as benign population polymorphisms (the >30 known TF structural variants, e.g., the common TF C1/C2/C3/B/D variant system used historically in population genetics/paternity testing) and are not disease-causing.

Allele frequency: No dedicated population allele frequency has been established for the rare pathogenic null alleles (consistent with an ultra-rare recessive disease); gnomAD/ExAC would be the appropriate resource to query per-variant frequencies, but published case reports do not cite population frequency data, reflecting the extreme rarity of biallelic loss-of-function TF genotypes.

Somatic vs. germline: Congenital atransferrinemia is strictly germline. Somatic/COSMIC-type data are not applicable (TF is not classically an oncogene/tumor suppressor in this context, though transferrin/transferrin receptor biology intersects with some cancer iron-dependency research unrelated to this Mendelian disease).

Functional consequences: The known variants produce loss of function — either through frameshift/deletion-insertion events that likely abolish protein production, or through missense substitutions (D77N, C137Y, A477P, P589S) that are presumed to destabilize the folded iron-binding lobes or impair secretion, resulting in absent-to-trace circulating transferrin. No gain-of-function or dominant-negative TF alleles have been reported for this disease.

Modifier genes: None specifically validated; clinical variability across cases (severity of anemia, degree of iron overload, response to therapy) likely reflects the amount of residual transferrin synthesized (complete absence vs. very low but detectable levels) rather than a distinct modifier locus.

Epigenetic information: No disease-specific DNA methylation or histone-modification studies of TF in atransferrinemia were identified; TF hepatic transcription is known generally to be regulated by inflammatory cytokines (as an acute-phase reactant that is down-regulated in inflammation) and by iron status via HNF and STAT pathways, which is relevant to the acquired form (see below) but has not been studied epigenetically in the congenital disease.

Chromosomal abnormalities: Not applicable — atransferrinemia is caused by point mutations/small indels within TF, not by large structural chromosomal rearrangements, aneuploidy, or copy-number changes.

5. Environmental Information

  • Environmental factors: None cause the congenital genetic disease; however, exogenous iron (dietary or parenteral) is a clinically important modifying exposure — iron supplementation is explicitly contraindicated because unbound iron cannot be used for erythropoiesis and instead exacerbates secondary hemosiderosis/hemochromatosis in liver, heart, pancreas, thyroid, and kidney.
  • Lifestyle factors: No specific dietary, smoking, exercise, or alcohol association data exist for this ultra-rare Mendelian disease.
  • Infectious agents: Not causal for the congenital form. Recurrent infections are a downstream consequence of the disease (possibly related to iron dysregulation impairing innate immune function, and/or to general debility), not a trigger of it.
  • Acquired ("secondary") atransferrinemia — a clinically distinct, non-genetic phenocopy — is triggered environmentally by severe chronic malnutrition, systemic inflammation, protein-losing/short-bowel enteropathy, and hepatic failure suppressing hepatic transferrin synthesis; it is reversible with treatment of the underlying condition (PMC9807235).

6. Mechanism / Pathophysiology

Causal chain (congenital form): 1. Trigger: Biallelic TF loss-of-function mutation → absent or near-absent hepatocyte-synthesized, secreted transferrin protein. 2. Molecular consequence: Failure of the normal transferrin–transferrin receptor 1 (TFRC/TfR1, OMIM 190010) cycle: without transferrin, iron cannot be delivered in its physiological, receptor-mediated, endocytosed form to erythroid precursors in the bone marrow. 3. Cellular consequence (erythroid): Erythroblasts are starved of iron for heme/hemoglobin synthesis despite whole-body iron sufficiency or excess → ineffective erythropoiesis → microcytic, hypochromic anemia. 4. Systemic consequence (iron handling): Dietary iron absorbed via duodenal enterocytes (via DMT1/ferroportin) has no transferrin "sink" to bind to in plasma; unbound iron circulates as non-transferrin-bound iron (NTBI). Intestinal DMT1 expression is paradoxically upregulated at the villus brush border in hypotransferrinemic states (mouse data), further increasing iron absorption despite tissue iron excess — an inappropriate absorption response driven by low circulating (rather than tissue) iron sensing and low hepcidin. 5. Tissue uptake of NTBI: NTBI is taken up avidly by parenchymal cells via ZIP14 (SLC39A14) in hepatocytes and pancreatic acinar cells, and via other transporters (e.g., L-type/T-type calcium channels in cardiomyocytes), producing secondary iron overload/hemosiderosis concentrated in liver, heart, pancreas, thyroid, and kidney — clinically the mirror image of primary hereditary hemochromatosis but occurring with concurrent severe anemia rather than normal hemoglobin. 6. Regulatory consequence: Transferrin is itself a major positive determinant of hepatic hepcidin expression (via holo-transferrin–driven TfR1/TfR2/HFE signaling); in its absence, hepcidin is inappropriately low, further permitting unchecked intestinal iron absorption and cellular iron efflux via ferroportin — a feed-forward loop that worsens tissue iron loading (PMID cluster on "Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice"). 7. End-organ damage: Chronic iron deposition in liver → fibrosis/cirrhosis; in heart → cardiomyopathy, arrhythmia, high-output failure (compounded by chronic anemia); in pancreas/thyroid → diabetes mellitus and hypothyroidism (a hemochromatosis-like endocrinopathy pattern). 8. Compensatory/alternative iron-delivery pathways* (relevant especially to milder/acquired cases): erythroid precursors and other cells can partially acquire iron independent of classical transferrin–TfR1 via ferritin-receptor pathways (TIM-1/HAVCR1, SCARA5, CXCR4), NTBI transporters (ZIP14, CD44), and direct macrophage-to-erythroblast iron transfer through the erythroblastic island "nurse macrophage" ferroportin-mediated route — explaining why some acquired-atransferrinemia patients maintain near-normal hemoglobin despite undetectable serum transferrin (PMC9807235).

Molecular pathways: Transferrin/transferrin receptor cycling (clathrin-mediated endocytosis pathway); hepcidin–ferroportin axis (systemic iron regulation, KEGG "Mineral absorption"/Reactome "Iron uptake and transport"); erythropoiesis and heme biosynthesis pathways (impaired due to iron-restricted erythropoiesis); NTBI uptake pathways (ZIP14/SLC39A14, L-type calcium channels).

Cellular processes: Ineffective erythropoiesis; iron-restricted heme synthesis; cellular iron overload–induced oxidative stress (Fenton-chemistry-driven reactive oxygen species) in hepatocytes, cardiomyocytes, and pancreatic acinar cells, leading to organelle damage, fibrogenesis, and eventual cell death/fibrosis (feeding into a fibrotic-response-type cascade in liver and heart).

Protein dysfunction: Loss of transferrin protein function — either failure of synthesis/secretion (frameshift/deletion-insertion alleles) or structural destabilization of the iron-binding lobes (missense alleles such as D77N, C137Y, A477P) impairing iron coordination or folding/secretion competence.

Metabolic changes: Iron metabolism is the central axis — low/absent plasma iron-transport capacity paired with tissue iron accumulation; secondary metabolic derangements can include impaired mitochondrial function in iron-overloaded hepatocytes and cardiomyocytes and, in the most severe neonatal-onset cases, associated lactic acidosis and aminoaciduria (PMID:10654962), suggesting broader mitochondrial/metabolic stress in profound neonatal presentations.

Immune system involvement: Recurrent infections are reported clinically; iron overload is known generally to impair neutrophil and lymphocyte function and to favor growth of siderophilic pathogens, though disease-specific immunology studies in atransferrinemia are lacking.

Tissue damage mechanisms: Oxidative stress from labile/catalytic tissue iron (Fenton chemistry generating hydroxyl radicals) driving hepatic fibrosis/cirrhosis and cardiomyopathy; anemia-driven tissue hypoxia (proposed mechanism for the hypospadias reported in one case, via fetal hypoxic insult to genital tubercle development).

Biochemical abnormalities: Absent/markedly reduced serum transferrin (<35 mg/dL vs. normal ~200–360 mg/dL), reduced total iron-binding capacity (TIBC), variably low serum iron in classic pediatric presentations (with markedly elevated ferritin reflecting tissue stores) or elevated serum iron with high transferrin saturation in others — the precise lab pattern differing somewhat across reported cases but always featuring a markedly abnormal iron/ferritin/transferrin triad.

Molecular profiling / advanced technologies: No transcriptomic, proteomic, metabolomic, single-cell, or spatial-transcriptomic studies specific to human atransferrinemia patient tissue were identified in the literature search — consistent with the extreme rarity of the disease and paucity of available biosamples. Model-organism work (mouse hpx, zebrafish gav) has substituted for human -omics data (see Model Organisms section).

Suggested GO terms: GO:0006826 (iron ion transport), GO:0033212 (iron assimilation), GO:0006879 (cellular iron ion homeostasis), GO:0055072 (iron ion homeostasis), GO:0034755 (iron ion transmembrane transport), GO:0033212 (iron uptake); GO Cellular Component: GO:0005576 (extracellular region, for secreted transferrin), GO:0031252 (cell leading edge, for TfR endocytosis machinery — verify applicability). Suggested CL terms: CL:0000765 (erythroblast), CL:0000037 (hematopoietic stem cell), CL:0000182 (hepatocyte), CL:0000138 (chondrocyte — n/a here), CL:0002496 (pancreatic acinar cell), CL:0000746 (cardiac muscle cell / cardiomyocyte).

7. Anatomical Structures Affected

Organ level: - Primary: Bone marrow (erythropoiesis failure) and liver (site of transferrin synthesis and major iron-overload target) - Secondary (iron deposition/complications): heart (cardiomyopathy, arrhythmia), pancreas (endocrine — diabetes), thyroid (hypothyroidism), kidney, joints (arthritis) - Body systems involved: hematologic/immune, hepatic/digestive, cardiovascular, endocrine, musculoskeletal

Tissue and cell level: - Erythroid precursor cells in bone marrow (CL:0000765 erythroblast) — primary site of the functional iron-deficiency lesion - Hepatocytes (CL:0000182) — site of transferrin synthesis (loss of function) and iron accumulation (hemosiderosis, fibrosis) - Pancreatic acinar/islet cells — NTBI uptake via ZIP14, leading to islet iron deposition and diabetes - Cardiomyocytes (CL:0000746) — NTBI uptake causing iron-overload cardiomyopathy - Reticuloendothelial (macrophage) system — normally receives senescent-RBC iron via transferrin-independent routes; may partially buffer NTBI

Subcellular level: Mitochondria (site of heme synthesis, impaired by iron-restricted erythropoiesis, and site of oxidative damage in iron-overloaded cells); lysosomes/endosomes (site of the normal transferrin–TfR1 endocytic iron-release cycle, which is absent given no transferrin cargo); cytosol/ferritin stores (site of accumulated iron in overloaded tissues).

Localization: Systemic/multi-organ rather than lateralized; no laterality pattern described.

Suggested UBERON terms: UBERON:0002106 (spleen), UBERON:0002107 (liver), UBERON:0000948 (heart), UBERON:0001264 (pancreas), UBERON:0002046 (thyroid gland), UBERON:0002371 (bone marrow), UBERON:0001021 (bone/joint — for arthritis).

8. Temporal Development

  • Onset: Typically infancy to early childhood; some cases present as early as birth (severe neonatal form with IUGR, lactic acidosis) and others are recognized incidentally later in childhood or even in the second decade (a 2021 report describes management "in the second decade" — PMID:34792309). Onset pattern is generally insidious (gradual anemia/pallor) rather than acute, though severe neonatal presentations can be fulminant.
  • Progression: Chronic and, without treatment, progressive — worsening anemia and accumulating tissue iron burden over years, with eventual hepatic fibrosis/cirrhosis and cardiac decompensation. With regular plasma/transferrin replacement therapy, disease course can be stabilized long-term (cases followed into the second decade of life under a "dynamic" fresh-frozen-plasma-plus-chelation approach).
  • Disease course pattern: Chronic and relapsing (dependent on regularity of plasma/transferrin infusions); if infusions lapse, anemia and iron indices worsen again. In the most severe neonatal cases, the course has been rapidly fatal (death at 8–10 weeks despite apotransferrin/exchange-transfusion therapy).
  • Critical periods: Early infancy appears to be the highest-risk window for mortality in the most severe genotypes; early diagnosis and initiation of plasma/apotransferrin therapy is critical to prevent irreversible cardiac and hepatic iron deposition.
  • Remission: No spontaneous remission described for the congenital form (it is a fixed genetic lesion); the reversible acquired form can fully normalize once the precipitating nutritional/inflammatory/hepatic condition resolves (PMC9807235).

9. Inheritance and Population

  • Inheritance pattern: Autosomal recessive (OMIM #209300); disease requires homozygous or compound heterozygous TF mutations. Heterozygous carriers are clinically asymptomatic.
  • Penetrance: Appears complete for biallelic loss-of-function genotypes, though severity varies (see below).
  • Expressivity: Variable — ranging from mild, incidentally discovered hypotransferrinemia with manageable anemia, to severe neonatal disease with multi-organ involvement and early death; likely correlates with residual transferrin synthetic capacity of the specific allele combination.
  • Genetic anticipation: Not described (not a repeat-expansion disorder).
  • Germline mosaicism: Not specifically reported in the literature reviewed.
  • Founder effects: Plausible given reported consanguineous kindreds (e.g., Turkish case) but no specific founder haplotype has been characterized in the literature surveyed.
  • Consanguinity: Documented in at least some reported families, consistent with autosomal recessive inheritance in an ultra-rare disease.
  • Carrier frequency: Not established; given fewer than ~20 kindreds reported worldwide, the disease is far rarer than can support a meaningful population carrier-frequency estimate from current data.

Epidemiology: - Prevalence: Unknown/not calculable; Orphanet lists prevalence as unknown. Cumulative literature reports approximately 16–20 cases from ~14–16 families worldwide since the first 1961 description, making this one of the rarest known inherited disorders of iron metabolism. - Incidence: Not established. - Affected populations: Cases reported across diverse populations/geographies, including the United States, Japan, Turkey, and other countries — no clear ethnic predilection has been established, though consanguinity in some reported families suggests regional clustering tied to specific consanguineous kindreds rather than a broad ethnic association. - Geographic distribution: Sporadic, worldwide case reports rather than an endemic pattern. - Sex ratio: No clear sex predilection reported (autosomal recessive, both male and female cases documented, e.g., hypospadias case is male, other reported cases are female). - Age distribution: Predominantly diagnosed in infancy/childhood, though later presentations (up to the second decade and beyond) have been documented.

10. Diagnostics

Clinical/laboratory tests: - Serum transferrin level: hallmark test; diagnostic threshold cited as serum TF <35 mg/dL (vs. normal ~200–360 mg/dL) - Complete blood count: severe microcytic, hypochromic anemia (hemoglobin as low as 5–6 g/dL in reported cases; MCV markedly reduced, e.g., 58–61 fL) - Serum iron: variably low or normal/elevated depending on case and disease stage - Total iron-binding capacity (TIBC): markedly reduced (reflecting absent transferrin) in most reports, though paradoxically some case series show TIBC within/near normal range with very low transferrin — likely reflecting assay/methodology differences and residual iron-binding proteins - Transferrin saturation (%): elevated/near-100% despite low absolute transferrin, because the small circulating pool is fully iron-saturated - Serum ferritin: markedly elevated (reported values of 1413–2072 µg/L against a normal range of ~45–160 µg/L), reflecting tissue iron stores - Imaging: liver/cardiac MRI (T2) can quantify tissue iron burden, analogous to its use in other iron-overload disorders (e.g., thalassemia, hemochromatosis) — not specifically detailed in the atransferrinemia literature reviewed but standard practice by extrapolation - Biopsy findings:* hepatic biopsy in affected patients would be expected to show iron deposition (hemosiderosis) with variable fibrosis; specific histopathology descriptions were not detailed in the sources reviewed here beyond general hemosiderosis references

Genetic testing: - Recommended approach: TF gene sequencing (single-gene test) is the diagnostic confirmatory test once biochemical findings (undetectable/very low transferrin with anemia and iron overload) raise suspicion; also available via targeted gene panels for inherited anemias/iron-overload disorders and via NCBI GTR-listed laboratory tests (GTR gene ID for TF: 7018) - Orphanet-listed diagnostic test: "Molecular diagnosis of atransferrinemia (TF gene)" (Orphanet test ID 367407) - WES/WGS: would be expected to detect TF variants but are not specifically required given the well-defined single-gene etiology; useful when initial targeted testing is uninformative or phenotype is atypical - Chromosomal microarray/karyotyping/FISH: not indicated — disease is due to intragenic point mutations/small indels, not large structural variants

Clinical criteria: No formal consensus diagnostic criteria/society guideline exists given the disease's rarity; diagnosis is based on the combination of (1) microcytic hypochromic anemia, (2) markedly low/absent serum transferrin with low TIBC, (3) elevated ferritin/tissue iron overload, and (4) confirmatory TF gene sequencing.

Differential diagnosis: Iron-deficiency anemia (distinguished by low, not high, ferritin); hemolytic anemias; congenital dyserythropoietic anemia; aceruloplasminemia (a differential also involving iron-transport dysfunction, but due to CP gene mutations affecting ferroxidase activity rather than transferrin itself); G6PD deficiency; hereditary hemochromatosis (distinguished by normal-to-high hemoglobin rather than severe anemia); acquired/secondary hypotransferrinemia from malnutrition, inflammation, or liver/enteric protein loss.

Screening: No newborn screening or population carrier-screening program exists for this ultra-rare disease; case-finding is via clinical recognition of the unusual anemia + iron-overload biochemical pattern, followed by targeted genetic confirmation and cascade testing of relatives.

11. Outcome/Prognosis

  • Survival/mortality: No formal survival statistics (5-year/10-year) exist given the extreme rarity of the disease; individual case outcomes vary widely. Severe neonatal-onset disease has been fatal within weeks (two infants died at 8 and 10 weeks of age despite apotransferrin and exchange-transfusion therapy in one report — PMID:10654962), whereas milder/later-onset cases treated with regular plasma or transferrin replacement have been followed successfully into the second decade of life and beyond (PMID:34792309).
  • Life expectancy: Historically, untreated disease "can be fatal" from cardiac and hepatic iron-overload complications; with modern plasma-infusion/chelation management, long-term survival into adulthood appears achievable, though comprehensive long-term outcome data are lacking.
  • Morbidity/functional outcomes: Chronic anemia-related fatigue and growth impairment in childhood; risk of hepatic fibrosis/cirrhosis, cardiomyopathy/arrhythmia, diabetes mellitus, and hypothyroidism as iron-overload sequelae if inadequately treated.
  • Complications: Secondary hemochromatosis-type organ damage (liver, heart, pancreas, thyroid); recurrent infections; possible developmental anomalies from fetal hypoxia in severe prenatal-onset disease (hypospadias case).
  • Recovery potential: With treatment (regular plasma/transferrin infusion ± chelation/phlebotomy), anemia and iron overload can be substantially improved (e.g., hemoglobin rising from 6.4 g/dL to >10 g/dL after apotransferrin dosing; ferritin declining from 1413 to 903 µg/L over 12 months of FFP therapy in one case). Without treatment, the disease is progressive and can be fatal.
  • Prognostic factors: Genotype/residual transferrin synthetic capacity, age at diagnosis/treatment initiation, adherence to regular infusion therapy, and degree of cardiac/hepatic iron deposition at the time treatment begins.

12. Treatment

Pharmacotherapy / plasma-based replacement (mainstay of treatment): - Fresh frozen plasma (FFP) infusion: Standard, most widely used therapy; provides exogenous transferrin. In one case series, monthly FFP produced reticulocytosis (6% at 2 weeks), hemoglobin rise to 12.4 g/dL at 1 month, and ferritin decline to 903 µg/L by 12 months (PMC5544637). - Apotransferrin (purified/iron-free transferrin) infusion: Used in several reported cases; an 8-year-old boy given 2 g apotransferrin (9.8% protein in normal saline) over three doses across 16 days had hemoglobin rise from 6.4 g/dL to >10 g/dL. Intravenous apotransferrin combined with exchange transfusion has also been trialed in severe neonatal-onset disease to normalize transferrin saturation, and was reported as "safe" though not lifesaving in that specific severe cohort (PMID:10654962). - Recombinant human transferrin: Mentioned in the literature as a treatment modality alongside plasma-derived transferrin, though clinical experience is limited given disease rarity. - Iron chelation therapy: Used adjunctively to manage secondary iron overload (e.g., deferoxamine/deferasirox-class agents), particularly in a "dynamic approach" combining FFP with iron-directed therapy described for maintaining hematologic stability into the second decade of life (PMID:34792309). - Phlebotomy: Mentioned as an adjunct to reduce iron burden in some management approaches, analogous to hemochromatosis management, though must be balanced against the patient's underlying anemia.

Contraindicated therapy: Direct iron supplementation is contraindicated — it does not correct the anemia (because erythroid iron utilization requires transferrin-mediated delivery) and instead worsens secondary hemosiderosis.

Surgical/interventional: No disease-specific surgical intervention beyond standard management of iron-overload complications (e.g., addressing hypospadias surgically if present as a congenital anomaly, unrelated to the core iron pathway).

Supportive/rehabilitative care: Management of growth, nutrition, and infection risk in affected children; endocrine management (thyroid hormone replacement, diabetes management) if hypothyroidism/diabetes develop from iron overload.

Experimental/investigational: No registered clinical trials specific to atransferrinemia were identified (consistent with its ultra-rarity precluding formal trial recruitment); management is based on case-report-level evidence and extrapolation from broader iron-overload/transfusion-dependent anemia management principles.

Treatment outcomes: Response to plasma/apotransferrin infusion is generally favorable for correcting anemia acutely, but the very severe neonatal genotype cohort described above did not survive despite treatment, indicating that genotype/disease severity and timing of intervention are critical determinants of outcome.

Suggested NCIT terms for treatment annotation: - NCIT:C15986 (Pharmacotherapy) — generic parent for plasma/transferrin/chelator administration - NCIT:C15747 (Supportive Care) - Blood product/plasma infusion does not have a precise dedicated NCIT clinical-action term in the standard set used here; would need specific lookup (e.g., "Fresh Frozen Plasma Transfusion" or "Plasma Exchange" terms) via NCIT search - Iron chelation therapy would be annotated under NCIT:C15986 (Pharmacotherapy) with therapeutic_agent bound to the specific chelator (e.g., CHEBI term for deferoxamine/deferasirox)

Treatment strategy: No formal treatment algorithm/guideline exists; management follows individualized case-based protocols combining regular transferrin/plasma replacement with iron-overload monitoring and adjunctive chelation, titrated to hemoglobin and ferritin/iron-saturation response.

13. Prevention

  • Primary prevention: Not applicable in the traditional sense (a fixed germline genetic disease); the only "primary prevention" avenue is genetic counseling and reproductive options (see below) for known carrier couples.
  • Secondary prevention: Early recognition of the anemia + iron-overload biochemical pattern to initiate transferrin/plasma replacement before irreversible cardiac/hepatic damage accrues; regular monitoring of ferritin, transferrin saturation, and cardiac/hepatic iron burden (e.g., T2* MRI) in known patients.
  • Tertiary prevention: Chelation therapy and dose-titrated plasma/transferrin replacement to prevent progression of established organ iron overload to fibrosis/cirrhosis and cardiomyopathy; endocrine surveillance (thyroid function, glucose tolerance) to catch and treat iron-overload endocrinopathy early.
  • Immunization: No disease-specific vaccine strategy; standard-of-care immunizations remain appropriate, and given the reported susceptibility to recurrent infections, timely routine vaccination and prompt treatment of infections are reasonable general measures (not disease-specific literature-supported recommendations).
  • Screening/early detection: No population or newborn screening program exists; case detection currently relies on clinical suspicion triggered by unexplained microcytic anemia with a disproportionately elevated ferritin/undetectable transferrin.
  • Genetic screening/counseling: For families with a known affected child or confirmed carrier status, genetic counseling regarding autosomal recessive recurrence risk (25% for future pregnancies of two carrier parents), carrier testing of at-risk relatives, and prenatal or preimplantation genetic testing options (where a familial pathogenic variant has been identified) are the standard reproductive-risk-management tools, by extrapolation from general recessive-disease practice (no atransferrinemia-specific prenatal testing literature was identified).
  • Risk stratification: Not formally developed for this disease.
  • Public health / environmental / prophylactic interventions: Not applicable to the congenital genetic form; for the acquired form, addressing underlying malnutrition, inflammatory disease, and hepatic dysfunction is itself the "preventive" strategy, since correcting those drivers reverses the acquired hypotransferrinemia.

14. Other Species / Natural Disease

  • Taxonomy: Mouse (Mus musculus, NCBITaxon:10090) and zebrafish (Danio rerio, NCBITaxon:7955) are the two species with well-characterized naturally occurring or induced Tf-deficiency models; no confirmed spontaneously occurring veterinary (companion animal/livestock) cases of atransferrinemia were identified in this search.
  • Gene orthologs: Mouse Trf (ortholog of human TF); zebrafish tfa (transferrin-a; zebrafish carry a teleost-specific duplicate, tfa/tfb, arising from genome duplication).
  • Natural disease:
  • Mouse hpx (hypotransferrinemic) strain: A spontaneous mutation originating in the BALB/cJ strain decades ago; Trf^hpx/hpx mice have <1% of normal plasma transferrin. The molecular defect is a point mutation at the exon 16 splice-donor site, abolishing normal Trf mRNA splicing (with only low-level aberrant transcripts produced via cryptic splice sites, including a predominant 27-bp in-frame deletion transcript) (PMID:10910930; original strain description PMID:3681112, "Hereditary hypotransferrinemia with hemosiderosis, a murine disorder resembling human atransferrinemia").
  • Zebrafish gavi (gav) mutant: Identified in a large-scale forward-genetic screen for hypochromic-anemia phenotypes; caused by mutations (alleles gav^IT029 and gav^HE067) producing aberrant splicing of the transferrin-a (tfa) transcript, closely phenocopying human congenital hypotransferrinemia including hypochromic anemia and, in the fish, embryonic lethality by ~14 days post-fertilization if untreated (PMID:19047682).
  • Veterinary relevance: No specific reports of naturally occurring atransferrinemia in companion animals or livestock were found in this search; the disease's veterinary significance is therefore primarily as a research model concept (mouse, zebrafish) rather than a recognized spontaneous veterinary disease entity.
  • Comparative biology/evolutionary conservation: The transferrin–TfR1 iron-delivery mechanism and the hepcidin–ferroportin regulatory axis are highly conserved across vertebrates, which is why both mouse and zebrafish models recapitulate the core human phenotype (anemia + iron mismanagement) faithfully, supporting cross-species mechanistic inference.
  • Transmission/zoonotic potential: Not applicable — a non-communicable, monogenic disorder.

15. Model Organisms

Model Type Genetic lesion Phenotype recapitulation Limitations Key reference
Mouse hpx (Trf^hpx/hpx), BALB/cJ background Spontaneous point mutation (induced/naturally arising model organism) Splice-donor site mutation after exon 16 of Trf, abolishing normal splicing; residual mRNA via cryptic splicing (27-bp in-frame deletion transcript) Severe anemia and tissue iron overload; mice die before weaning unless treated with exogenous transferrin or RBC transfusion — closely mirrors human disease severity and dual anemia/iron-overload phenotype; also shows compensatory intestinal DMT1 upregulation, informative for the human NTBI-absorption mechanism Neonatal lethality without intervention makes long-term/adult study harder without rescue treatment; species differences in iron physiology (e.g., placental iron transfer, dietary patterns) may limit some translational inferences PMID:3681112 (original description); PMID:10910930 (molecular defect); additional hepcidin/DMT1 mechanistic studies in hpx mice
Zebrafish gavi (gav) mutant, alleles gav^IT029/gav^HE067 Induced/naturally arising mutant (forward genetic screen) Mutations causing aberrant splicing of transferrin-a (tfa) Hypochromic anemia and (if untreated) embryonic/larval lethality by ~14 dpf; morpholino knockdown of tfa reproduces the anemia and reduced tissue iron staining phenotype, and this is rescued by tfa cRNA co-injection — a strong causality/rescue demonstration Zebrafish possess a duplicated transferrin gene (tfa/tfb) from teleost genome duplication, an evolutionary difference from the single human TF gene; external embryonic development and high fecundity make it excellent for early-development and high-throughput screening studies but less suited to modeling adult-onset organ complications (cardiomyopathy, cirrhosis, endocrinopathy) seen in human patients PMID:19047682

Applications: Both models have been used to dissect (1) the erythropoiesis defect caused by iron-restricted heme synthesis, (2) the compensatory/dysregulated intestinal iron absorption response (DMT1 upregulation in mouse), and (3) the hepcidin-suppression mechanism that drives secondary iron overload — directly informing the pathophysiological model described in Section 6. The zebrafish model in particular has been leveraged for genetic and morpholino-based mechanistic dissection given the ease of embryonic manipulation and imaging.

Resources: Mouse Genome Informatics (MGI) for the Trf^hpx allele; ZFIN for the zebrafish gav mutant allele records.

Summary for Knowledge-Base Curation

Atransferrinemia is a well-bounded, single-gene (TF, chromosome 3q22.1), autosomal recessive disorder (OMIM #209300 / ORPHA:1195) with a clear, well-documented causal chain: TF loss-of-function mutation → absent/low plasma transferrin → failure of transferrin-receptor–mediated iron delivery to erythroid precursors (microcytic/hypochromic anemia) in parallel with unregulated NTBI uptake via ZIP14 and low hepcidin → secondary iron overload in liver, heart, pancreas, thyroid, and kidney. It has strong, cross-species mechanistic validation from both the classical mouse hpx strain and the zebrafish gavi mutant, several molecularly characterized human cases with specific pathogenic TF variants (D77N, C137Y, A477P, and a deletion-insertion allele), and an established (if evidence-limited, given disease rarity) treatment paradigm centered on plasma/apotransferrin replacement plus iron chelation, with iron supplementation specifically contraindicated. A distinct, environmentally triggered and reversible "acquired atransferrinemia" phenocopy (malnutrition/inflammation/liver failure) should be modeled or annotated separately from the congenital genetic disease, and its physiology (near-normal hemoglobin despite absent transferrin) offers useful mechanistic contrast highlighting non-canonical/compensatory iron-delivery pathways.

Sources: - Entry - #209300 - ATRANSFERRINEMIA - OMIM - Entry - *190000 - TRANSFERRIN; TF - OMIM - Orphanet: Congenital atransferrinemia (ORPHA:1195) - Orphanet: TF-transferrin - Atransferrinemia - Symptoms, Causes, Treatment | NORD - Atransferrinemia | About the Disease | GARD - Atransferrinemia - Wikipedia - Atransferrinemia - an overview | ScienceDirect Topics - Congenital Hypotransferrinemia, an Unusual Cause of Iron Deficiency Anemia: Report of Two Cases - PMC (PMID:28824244) - A Rare Case of Congenital Atransferrinemia: International Collaboration for Genetic Diagnosis | Blood - Molecular characterization of a case of atransferrinemia | Blood (PMID:11110675) - Molecular characterization of a third case of human atransferrinemia | Blood (PMID:15466165) - A new case of human atransferrinemia with a previously undescribed mutation in the transferrin gene - PubMed (PMID:18097132) - Exogenous apotransferrin and exchange transfusions in hereditary iron overload disease - PubMed (PMID:10654962) - Fresh Frozen Plasma Plus Iron Therapy in Congenital Hypotransferrinemia in the Second Decade - PubMed (PMID:34792309) - Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport? - PMC (PMID:9807235 article) - Transferrin-a modulates hepcidin expression in zebrafish embryos - PubMed (PMID:19047682) - The molecular defect in hypotransferrinemic mice - PubMed (PMID:10910930) - Hereditary hypotransferrinemia with hemosiderosis, a murine disorder resembling human atransferrinemia - PubMed (PMID:3681112) - Transferrin is a major determinant of hepcidin expression in hypotransferrinemic mice | Blood - Zip14 (Slc39a14) mediates non-transferrin-bound iron uptake into cells | PNAS - TF transferrin - NIH Genetic Testing Registry (GTR) - NCBI - NM_001063.4(TF):c.1765C>T (p.Pro589Ser) AND Atransferrinemia - ClinVar - NM_001063.3(TF):c.-117G>A AND Atransferrinemia - ClinVar - NM_001063.4(TF):c.229G>A (p.Asp77Asn) AND Atransferrinemia - ClinVar