👪

Inheritance

1

Autosomal recessive inheritance HP:0000007

Hereditary intrinsic factor deficiency is caused by recessive CBLIF/GIF variants, with affected individuals carrying biallelic pathogenic alleles.

Autosomal recessive inheritance

Show evidence (1 reference)

DOI:10.1073/pnas.0500517102 SUPPORT Human Clinical

"The gastric IF ( GIF ) gene located in this region harbored homozygous nonsense and missense mutations in these four families and in three additional families."

The family series identified homozygous GIF variants in multiple affected kindreds, supporting recessive inheritance of intrinsic factor deficiency.

⚙

Pathophysiology

4

CBLIF-related intrinsic factor loss

Pathogenic CBLIF/GIF variation reduces or abolishes functional gastric intrinsic factor, preventing normal binding and intestinal uptake of dietary cobalamin.

gastric parietal cell link

CBLIF link

cobalamin transport link ↓ DECREASED

Downstream

Impaired intrinsic factor-dependent cobalamin absorption Loss of functional intrinsic factor prevents effective absorption of dietary cobalamin.

Show evidence (2 references)

DOI:10.1182/blood-2003-07-2239 SUPPORT Human Clinical

"A 4-base deletion has been identified in the coding region of the gene for gastric intrinsic factor (IF) in an 11-year-old girl with severe anemia and cobalamin (Cbl) deficiency."

This case report directly links an intrinsic factor gene deletion to severe anemia and cobalamin deficiency.

PMID:25308559 SUPPORT Human Clinical

"Intrinsic factor deficiency (OMIM #261000, IFD) is a rare inherited disorder of vitamin B12 metabolism due to mutations in the gastric intrinsic factor (GIF) gene."

The Old Order Mennonite case series supports GIF mutation as the upstream cause of inherited intrinsic factor deficiency.

Impaired intrinsic factor-dependent cobalamin absorption

Intrinsic-factor-dependent cobalamin transport failure depletes systemic vitamin B12 and disrupts downstream one-carbon and methylmalonic acid metabolism.

ileal enterocyte link

cobalamin transport link ↓ DECREASED one-carbon metabolic process link ⚠ ABNORMAL

Downstream

Biochemical cobalamin deficiency pattern Defective cobalamin absorption lowers serum vitamin B12 and can increase methylmalonic acid and homocysteine.

Megaloblastic erythropoietic failure Cobalamin depletion impairs DNA synthesis during erythropoiesis, producing megaloblastic anemia.

Show evidence (2 references)

PMID:22929189 SUPPORT Human Clinical

"Recessive mutations in CUBN or AMN cause Imerslund-Gräsbeck Syndrome (IGS), while recessive mutations in GIF cause Intrinsic Factor Deficiency (IFD)."

The large hereditary cobalamin malabsorption cohort separates GIF-caused intrinsic factor deficiency from receptor-mediated IGS.

DOI:10.3390/ijms25158021 PARTIAL Other

"Thus, this review aims to compile current knowledge about the crucial proteins necessary to efficiently accumulate and process vitamin B12 in humans, presenting these systems as a multi-protein network."

The 2024 review provides a current pathway synthesis for vitamin B12 absorption and processing; the Falcon artifact image directly illustrates the intrinsic-factor-dependent absorption pathway.

Biochemical cobalamin deficiency pattern

Impaired intrinsic factor-dependent absorption lowers serum cobalamin and produces the downstream biochemical pattern of methylmalonic acid and homocysteine accumulation.

cobalamin metabolic process link ⚠ ABNORMAL one-carbon metabolic process link ⚠ ABNORMAL

Downstream

Megaloblastic erythropoietic failure Cobalamin-dependent biochemical disruption impairs bone marrow erythropoiesis.

Gastrointestinal symptoms Systemic cobalamin deficiency from congenital absorption disorders can manifest with gastrointestinal symptoms.

Neurological abnormalities Inherited cobalamin malabsorption can produce neurologic manifestations through downstream effects of cobalamin deficiency.

Show evidence (2 references)

PMID:25308559 SUPPORT Human Clinical

"Serum B12 was 61 (198-615 pmol/L)."

The low serum B12 measurement supports systemic cobalamin deficiency downstream of intrinsic factor loss.

PMID:22854512 SUPPORT Human Clinical

"These disorders lead to intracellular Cbl depletion which in turn causes megaloblastic bone marrow failure, accumulation of homocysteine and methylmalonic acid (MMA), and methionine depletion."

The inherited B12 absorption-disorder cohort supports the biochemical pattern linking cobalamin depletion to homocysteine and methylmalonic acid accumulation.

Megaloblastic erythropoietic failure

Vitamin B12 depletion disrupts erythroblast maturation, causing macrocytic or megaloblastic anemia and sometimes broader marrow failure.

erythroblast link

erythrocyte differentiation link ⚠ ABNORMAL

Downstream

Megaloblastic anemia Megaloblastic erythropoietic failure produces the hallmark megaloblastic anemia phenotype.

Macrocytic anemia Megaloblastic cobalamin-deficiency anemia falls within the macrocytic-anemia spectrum.

Pancytopenia Severe cobalamin-related marrow failure can broaden beyond anemia to pancytopenia.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"He had pancytopenia with megaloblastic anemia."

This patient-level observation supports megaloblastic erythropoietic failure as a downstream manifestation of intrinsic factor deficiency.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

5

Blood 3

Megaloblastic anemia Megaloblastic anemia (HP:0001889)

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"A high index of suspicion should be maintained if children present with megaloblastic anemia since GIF deficiency is a treatable disorder and newborn screening may not be able to detect this condition."

The case series explicitly identifies megaloblastic anemia as a key presentation requiring suspicion for GIF deficiency.

Macrocytic anemia Macrocytic anemia (HP:0001972)

Show evidence (1 reference)

DOI:10.1073/pnas.0500517102 SUPPORT Human Clinical

"Hereditary juvenile megaloblastic anemia due to vitamin B 12 (cobalamin) deficiency is caused by intestinal malabsorption of cobalamin."

This supports the cobalamin-malabsorption anemia phenotype that maps to the macrocytic/megaloblastic anemia spectrum.

Pancytopenia Pancytopenia (HP:0001876)

Show evidence (1 reference)

PMID:22854512 SUPPORT Human Clinical

"The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia."

The treatment cohort review supports pancytopenia as part of the clinical presentation of inborn errors of vitamin B12 absorption including HIFD.

Nervous System 1

Neurological abnormalities Abnormality of the nervous system (HP:0000707)

Show evidence (1 reference)

PMID:22929189 SUPPORT Human Clinical

"Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal."

The hereditary cobalamin malabsorption cohort supports neurologic abnormalities as part of the disease spectrum when cobalamin absorption is genetically impaired.

Other 1

Gastrointestinal symptoms Abdominal symptom (HP:0011458)

Show evidence (1 reference)

PMID:22854512 SUPPORT Human Clinical

"The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia."

The inherited B12 absorption-disorder cohort directly identifies gastrointestinal symptoms among the clinical manifestations.

🧬

Genetic Associations

1

CBLIF/GIF pathogenic variants

Autosomal recessive

Show evidence (1 reference)

PMID:22929189 SUPPORT Human Clinical

"We identified mutations in 126/154 unrelated cases (82%). Fifty-three of 126 cases (42%) were mutated in CUBN, 45/126 (36%) were mutated in AMN, and 28/126 (22%) had mutations in GIF."

The large molecular screening cohort supports GIF as one of the three causal genes for inherited cobalamin malabsorption.

💊

Treatments

1

Lifelong vitamin B12 replacement

Action: vitamin supplementation MAXO:0001129

Agent: hydroxocobalamin ↗

Lifelong vitamin B12 replacement bypasses defective intrinsic factor availability and prevents or reverses hematologic and biochemical consequences of cobalamin malabsorption. Published cases include response to oral as well as parenteral vitamin B12, consistent with the treatment bypassing intrinsic factor-dependent absorption when sufficiently dosed.

Mechanism Target:

BYPASSES Impaired intrinsic factor-dependent cobalamin absorption — Pharmacologic vitamin B12 replacement bypasses the defective intrinsic-factor-dependent absorption step, especially when delivered parenterally.

Show evidence (1 reference)

PMID:22854512 SUPPORT Human Clinical

"Accurate diagnosis is always an emergency because early detection and treatment with life-long parenteral pharmacological doses of hydroxocobalamin are life saving and prevent further deterioration."

The cobalamin-absorption-disorder cohort supports parenteral hydroxocobalamin as a disease-modifying route that bypasses the absorption defect.

RESTORES Biochemical cobalamin deficiency pattern — Vitamin B12 replacement restores cobalamin availability and normalizes hematologic and metabolic markers with appropriate follow-up.

Show evidence (1 reference)

PMID:22854512 SUPPORT Human Clinical

"Unlike previous recommendations, we showed that a maintenance dosage of 1 mg cobalamin twice a year was enough to ensure a normal clinical status and keep the hematological and metabolic parameters in the normal range."

The maintenance-therapy cohort supports cobalamin replacement as sufficient to maintain normal clinical, hematologic, and metabolic parameters in inherited B12 absorption disorders.

RESTORES Megaloblastic erythropoietic failure — Vitamin B12 replacement restores hematologic output when anemia is driven by inherited intrinsic factor deficiency.

Show evidence (1 reference)

DOI:10.1186/s12881-020-01158-z SUPPORT Human Clinical

"The hemoglobin level normalized each time after intramuscular vitamin B12 injection."

This HIFD case report supports vitamin B12 replacement as restoring the downstream anemia caused by cobalamin malabsorption.

Show evidence (2 references)

PMID:25308559 SUPPORT Human Clinical

"Oral or parenteral vitamin B12 has led to complete recovery of clinical parameters and vitamin B12 levels."

The GIF-deficiency case series supports vitamin B12 replacement as an effective treatment.

PMID:22854512 SUPPORT Human Clinical

"Accurate diagnosis is always an emergency because early detection and treatment with life-long parenteral pharmacological doses of hydroxocobalamin are life saving and prevent further deterioration."

The inherited absorption-disorder treatment cohort supports lifelong parenteral hydroxocobalamin as disease-modifying therapy.

🔬

Biochemical Markers

3

Serum cobalamin (DECREASED)

Context: Low serum vitamin B12 is the proximal biochemical abnormality caused by intrinsic-factor-dependent absorption failure.

Pathograph Readouts

Readout Of Impaired intrinsic factor-dependent cobalamin absorption Negative Diagnostic

Low serum cobalamin reports failure of intrinsic-factor-dependent cobalamin absorption.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Serum B12 was 61 (198-615 pmol/L)."

The low serum B12 measurement supports serum cobalamin as a diagnostic readout of the absorption-failure mechanism.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Serum B12 was 61 (198-615 pmol/L)."

The reported serum B12 value supports decreased circulating cobalamin in GIF deficiency.

Methylmalonic acid (INCREASED)

Context: Methylmalonic aciduria reflects downstream disruption of vitamin B12-dependent metabolism.

Pathograph Readouts

Readout Of Biochemical cobalamin deficiency pattern Positive Diagnostic

Increased methylmalonic acid reports impaired cobalamin-dependent metabolism in the biochemical deficiency state.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Methylmalonic aciduria was present."

The case series documents methylmalonic aciduria as a positive diagnostic readout of the biochemical cobalamin-deficiency pattern.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Methylmalonic aciduria was present."

The case series documents methylmalonic aciduria as a biochemical consequence of intrinsic factor deficiency.

Homocysteine (INCREASED)

Context: Hyperhomocysteinemia is a downstream marker of impaired cobalamin-dependent one-carbon metabolism.

Pathograph Readouts

Readout Of Biochemical cobalamin deficiency pattern Positive Diagnostic

Elevated homocysteine reports impaired cobalamin-dependent one-carbon metabolism in the biochemical deficiency state.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Homocysteine was high at 16.7 (5.0-12.0 umol/L)."

The reported hyperhomocysteinemia supports homocysteine as a positive diagnostic readout of the biochemical cobalamin-deficiency pattern.

Show evidence (1 reference)

PMID:25308559 SUPPORT Human Clinical

"Homocysteine was high at 16.7 (5.0-12.0 umol/L)."

The reported elevated homocysteine supports abnormal cobalamin-dependent one-carbon metabolism.

🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Hereditary intrinsic factor deficiency:

Imerslund-Gräsbeck syndrome

Overlapping Features Imerslund-Gräsbeck syndrome causes inherited cobalamin malabsorption through CUBN or AMN receptor defects rather than intrinsic factor deficiency.

Distinguishing Features

Proteinuria is typical of Imerslund-Gräsbeck syndrome and is usually absent in intrinsic factor deficiency.
Receptor-gene defects in CUBN or AMN distinguish IGS from CBLIF/GIF-related intrinsic factor deficiency.

Show evidence (1 reference)

PMID:22929189 SUPPORT Human Clinical

"IGS and IFD differ in that IGS usually presents with proteinuria, which is not observed in IFD."

The hereditary cobalamin malabsorption cohort directly supports proteinuria as a distinguishing feature between IGS and intrinsic factor deficiency.

{ }

Source YAML

click to show

name: Hereditary intrinsic factor deficiency
creation_date: "2026-05-14T18:22:33Z"
updated_date: "2026-05-19T06:28:48Z"
synonyms:
- congenital intrinsic factor deficiency
- inherited intrinsic factor deficiency
- congenital pernicious anemia
- gastric intrinsic factor deficiency
- hereditary juvenile megaloblastic anemia due to intrinsic factor deficiency
description: >-
  Hereditary intrinsic factor deficiency is a rare autosomal recessive disorder
  of selective cobalamin absorption caused by pathogenic variants in CBLIF
  (historically GIF), the gastric intrinsic factor gene. Deficient intrinsic
  factor prevents normal vitamin B12 uptake, leading to low cobalamin,
  methylmalonic aciduria and hyperhomocysteinemia, megaloblastic anemia, and
  risk of neurologic injury if treatment is delayed. Lifelong vitamin B12
  replacement is disease modifying and can normalize clinical, hematologic, and
  biochemical parameters.
category: Mendelian
parents:
- hereditary anemia
- inborn disorder of cobalamin metabolism and transport
disease_term:
  preferred_term: hereditary intrinsic factor deficiency
  term:
    id: MONDO:0009852
    label: hereditary intrinsic factor deficiency
inheritance:
- name: Autosomal recessive inheritance
  description: >-
    Hereditary intrinsic factor deficiency is caused by recessive CBLIF/GIF
    variants, with affected individuals carrying biallelic pathogenic alleles.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: DOI:10.1073/pnas.0500517102
    reference_title: "Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The gastric IF (
                          GIF
                          ) gene located in this region harbored homozygous nonsense and missense mutations in these four families and in three additional families.
    explanation: >-
      The family series identified homozygous GIF variants in multiple affected
      kindreds, supporting recessive inheritance of intrinsic factor deficiency.
pathophysiology:
- name: CBLIF-related intrinsic factor loss
  description: >-
    Pathogenic CBLIF/GIF variation reduces or abolishes functional gastric
    intrinsic factor, preventing normal binding and intestinal uptake of dietary
    cobalamin.
  genes:
  - preferred_term: CBLIF
    term:
      id: hgnc:4268
      label: CBLIF
  cell_types:
  - preferred_term: gastric parietal cell
    term:
      id: CL:0000162
      label: parietal cell
  biological_processes:
  - preferred_term: cobalamin transport
    modifier: DECREASED
    term:
      id: GO:0015889
      label: cobalamin transport
  evidence:
  - reference: DOI:10.1182/blood-2003-07-2239
    reference_title: "Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A 4-base deletion has been identified in the coding region of the gene for gastric intrinsic factor (IF) in an 11-year-old girl with severe anemia and cobalamin (Cbl) deficiency.
    explanation: >-
      This case report directly links an intrinsic factor gene deletion to
      severe anemia and cobalamin deficiency.
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Intrinsic factor deficiency (OMIM #261000, IFD) is a rare inherited disorder of vitamin B12 metabolism due to mutations in the gastric intrinsic factor (GIF) gene."
    explanation: >-
      The Old Order Mennonite case series supports GIF mutation as the upstream
      cause of inherited intrinsic factor deficiency.
  downstream:
  - target: Impaired intrinsic factor-dependent cobalamin absorption
    description: >-
      Loss of functional intrinsic factor prevents effective absorption of
      dietary cobalamin.
    causal_link_type: DIRECT
    evidence:
    - reference: DOI:10.1182/blood-2003-07-2239
      reference_title: "Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The bone marrow showed frank megaloblastic morphology, and the Schilling test indicated a failure to absorb Cbl that was corrected by coadministration of IF.
      explanation: >-
        Correction of cobalamin absorption by intrinsic factor supports the
        direct causal link from IF loss to impaired absorption.
- name: Impaired intrinsic factor-dependent cobalamin absorption
  description: >-
    Intrinsic-factor-dependent cobalamin transport failure depletes systemic
    vitamin B12 and disrupts downstream one-carbon and methylmalonic acid
    metabolism.
  cell_types:
  - preferred_term: ileal enterocyte
    term:
      id: CL:0000584
      label: enterocyte
  biological_processes:
  - preferred_term: cobalamin transport
    modifier: DECREASED
    term:
      id: GO:0015889
      label: cobalamin transport
  - preferred_term: one-carbon metabolic process
    modifier: ABNORMAL
    term:
      id: GO:0006730
      label: one-carbon metabolic process
  evidence:
  - reference: PMID:22929189
    reference_title: "Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recessive mutations in CUBN or AMN cause Imerslund-Gräsbeck Syndrome (IGS), while recessive mutations in GIF cause Intrinsic Factor Deficiency (IFD).
    explanation: >-
      The large hereditary cobalamin malabsorption cohort separates GIF-caused
      intrinsic factor deficiency from receptor-mediated IGS.
  - reference: DOI:10.3390/ijms25158021
    reference_title: "Vitamin B12 Metabolism: A Network of Multi-Protein Mediated Processes"
    supports: PARTIAL
    evidence_source: OTHER
    snippet: >-
      Thus, this review aims to compile current knowledge about the crucial proteins necessary to efficiently accumulate and process vitamin B12 in humans, presenting these systems as a multi-protein network.
    explanation: >-
      The 2024 review provides a current pathway synthesis for vitamin B12
      absorption and processing; the Falcon artifact image directly illustrates
      the intrinsic-factor-dependent absorption pathway.
    images:
    - Hereditary_Intrinsic_Factor_Deficiency-deep-research-falcon_artifacts/image-1.png
  downstream:
  - target: Biochemical cobalamin deficiency pattern
    description: >-
      Defective cobalamin absorption lowers serum vitamin B12 and can increase
      methylmalonic acid and homocysteine.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Serum B12 was 61 (198-615 pmol/L). Methylmalonic aciduria was present. C3 was elevated on acylcarnitine profile. Homocysteine was high at 16.7 (5.0-12.0 umol/L).
      explanation: >-
        The GIF-deficiency case series documents the low serum B12,
        methylmalonic aciduria, and hyperhomocysteinemia pattern downstream of
        inherited intrinsic-factor-dependent absorption failure.
  - target: Megaloblastic erythropoietic failure
    description: >-
      Cobalamin depletion impairs DNA synthesis during erythropoiesis, producing
      megaloblastic anemia.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22854512
      reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These disorders lead to intracellular Cbl depletion which in turn causes megaloblastic bone marrow failure, accumulation of homocysteine and methylmalonic acid (MMA), and methionine depletion.
      explanation: >-
        The inherited cobalamin-absorption cohort directly links Cbl depletion
        from absorption disorders to megaloblastic bone marrow failure.
- name: Biochemical cobalamin deficiency pattern
  description: >-
    Impaired intrinsic factor-dependent absorption lowers serum cobalamin and
    produces the downstream biochemical pattern of methylmalonic acid and
    homocysteine accumulation.
  biological_processes:
  - preferred_term: cobalamin metabolic process
    modifier: ABNORMAL
    term:
      id: GO:0009235
      label: cobalamin metabolic process
  - preferred_term: one-carbon metabolic process
    modifier: ABNORMAL
    term:
      id: GO:0006730
      label: one-carbon metabolic process
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serum B12 was 61 (198-615
      pmol/L).
    explanation: >-
      The low serum B12 measurement supports systemic cobalamin deficiency
      downstream of intrinsic factor loss.
  - reference: PMID:22854512
    reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These disorders lead to intracellular Cbl depletion which in
      turn causes megaloblastic bone marrow failure, accumulation of homocysteine and
      methylmalonic acid (MMA), and methionine depletion.
    explanation: >-
      The inherited B12 absorption-disorder cohort supports the biochemical
      pattern linking cobalamin depletion to homocysteine and methylmalonic acid
      accumulation.
  downstream:
  - target: Megaloblastic erythropoietic failure
    description: >-
      Cobalamin-dependent biochemical disruption impairs bone marrow
      erythropoiesis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22854512
      reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These disorders lead to intracellular Cbl depletion which in turn causes megaloblastic bone marrow failure, accumulation of homocysteine and methylmalonic acid (MMA), and methionine depletion.
      explanation: >-
        This supports megaloblastic marrow failure as a downstream consequence
        of the intracellular cobalamin-depletion biochemical state.
  - target: Gastrointestinal symptoms
    description: >-
      Systemic cobalamin deficiency from congenital absorption disorders can
      manifest with gastrointestinal symptoms.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22854512
      reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia.
      explanation: >-
        The cohort summary states that gastrointestinal symptoms reflect the
        underlying cobalamin-deficiency state.
  - target: Neurological abnormalities
    description: >-
      Inherited cobalamin malabsorption can produce neurologic manifestations
      through downstream effects of cobalamin deficiency.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22929189
      reference_title: "Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal.
      explanation: >-
        The hereditary cobalamin-malabsorption cohort links the inherited
        absorption defect to neurologic abnormalities.
- name: Megaloblastic erythropoietic failure
  description: >-
    Vitamin B12 depletion disrupts erythroblast maturation, causing macrocytic
    or megaloblastic anemia and sometimes broader marrow failure.
  cell_types:
  - preferred_term: erythroblast
    term:
      id: CL:0000765
      label: erythroblast
  biological_processes:
  - preferred_term: erythrocyte differentiation
    modifier: ABNORMAL
    term:
      id: GO:0030218
      label: erythrocyte differentiation
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      He had pancytopenia with megaloblastic anemia.
    explanation: >-
      This patient-level observation supports megaloblastic erythropoietic
      failure as a downstream manifestation of intrinsic factor deficiency.
  downstream:
  - target: Megaloblastic anemia
    description: >-
      Megaloblastic erythropoietic failure produces the hallmark
      megaloblastic anemia phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        He had pancytopenia with megaloblastic anemia.
      explanation: >-
        The patient-level observation directly supports megaloblastic anemia as
        the clinical expression of the erythropoietic failure node.
  - target: Macrocytic anemia
    description: >-
      Megaloblastic cobalamin-deficiency anemia falls within the
      macrocytic-anemia spectrum.
    causal_link_type: DIRECT
    evidence:
    - reference: DOI:10.1073/pnas.0500517102
      reference_title: "Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Hereditary juvenile megaloblastic anemia due to vitamin B 12 (cobalamin) deficiency is caused by intestinal malabsorption of cobalamin.
      explanation: >-
        The family study supports cobalamin-malabsorption megaloblastic anemia,
        which is the macrocytic anemia pattern represented by this phenotype.
  - target: Pancytopenia
    description: >-
      Severe cobalamin-related marrow failure can broaden beyond anemia to
      pancytopenia.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        He had pancytopenia with megaloblastic anemia.
      explanation: >-
        The same GIF-deficiency case directly reports pancytopenia with the
        megaloblastic anemia presentation.
phenotypes:
- name: Megaloblastic anemia
  category: Hematologic
  diagnostic: true
  description: >-
    Megaloblastic anemia is the hallmark hematologic presentation of hereditary
    intrinsic factor deficiency.
  phenotype_term:
    preferred_term: Megaloblastic anemia
    term:
      id: HP:0001889
      label: Megaloblastic anemia
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A high index of suspicion should be maintained if children present with megaloblastic anemia since GIF deficiency is a treatable disorder and newborn screening may not be able to detect this condition.
    explanation: >-
      The case series explicitly identifies megaloblastic anemia as a key
      presentation requiring suspicion for GIF deficiency.
- name: Macrocytic anemia
  category: Hematologic
  description: >-
    Macrocytic anemia can accompany the megaloblastic marrow phenotype.
  phenotype_term:
    preferred_term: Macrocytic anemia
    term:
      id: HP:0001972
      label: Macrocytic anemia
  evidence:
  - reference: DOI:10.1073/pnas.0500517102
    reference_title: "Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hereditary juvenile megaloblastic anemia due to vitamin B
                          12
                          (cobalamin) deficiency is caused by intestinal malabsorption of cobalamin.
    explanation: >-
      This supports the cobalamin-malabsorption anemia phenotype that maps to
      the macrocytic/megaloblastic anemia spectrum.
- name: Pancytopenia
  category: Hematologic
  description: >-
    Severe cobalamin deficiency from intrinsic factor deficiency can produce
    pancytopenia.
  phenotype_term:
    preferred_term: Pancytopenia
    term:
      id: HP:0001876
      label: Pancytopenia
  evidence:
  - reference: PMID:22854512
    reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia.
    explanation: >-
      The treatment cohort review supports pancytopenia as part of the clinical
      presentation of inborn errors of vitamin B12 absorption including HIFD.
- name: Gastrointestinal symptoms
  category: Gastrointestinal
  description: >-
    Gastrointestinal symptoms can accompany inherited vitamin B12 absorption
    disorders, including hereditary intrinsic factor deficiency.
  phenotype_term:
    preferred_term: Gastrointestinal symptoms
    term:
      id: HP:0011458
      label: Abdominal symptom
  evidence:
  - reference: PMID:22854512
    reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia.
    explanation: >-
      The inherited B12 absorption-disorder cohort directly identifies
      gastrointestinal symptoms among the clinical manifestations.
- name: Neurological abnormalities
  category: Neurologic
  description: >-
    Untreated inherited cobalamin malabsorption can produce neurologic
    manifestations and long-term neurologic complications.
  phenotype_term:
    preferred_term: Neurological abnormalities
    term:
      id: HP:0000707
      label: Abnormality of the nervous system
  evidence:
  - reference: PMID:22929189
    reference_title: "Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal.
    explanation: >-
      The hereditary cobalamin malabsorption cohort supports neurologic
      abnormalities as part of the disease spectrum when cobalamin absorption is
      genetically impaired.
biochemical:
- name: Serum cobalamin
  presence: DECREASED
  context: >-
    Low serum vitamin B12 is the proximal biochemical abnormality caused by
    intrinsic-factor-dependent absorption failure.
  biomarker_term:
    preferred_term: cobalamin
    term:
      id: CHEBI:30411
      label: cobalamin
  readouts:
  - target: Impaired intrinsic factor-dependent cobalamin absorption
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Low serum cobalamin reports failure of intrinsic-factor-dependent
      cobalamin absorption.
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Serum B12 was 61 (198-615 pmol/L).
      explanation: >-
        The low serum B12 measurement supports serum cobalamin as a diagnostic
        readout of the absorption-failure mechanism.
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Serum B12 was 61 (198-615
      pmol/L).
    explanation: >-
      The reported serum B12 value supports decreased circulating cobalamin in
      GIF deficiency.
- name: Methylmalonic acid
  presence: INCREASED
  context: >-
    Methylmalonic aciduria reflects downstream disruption of vitamin
    B12-dependent metabolism.
  biomarker_term:
    preferred_term: methylmalonic acid
    term:
      id: CHEBI:30860
      label: methylmalonic acid
  readouts:
  - target: Biochemical cobalamin deficiency pattern
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Increased methylmalonic acid reports impaired cobalamin-dependent
      metabolism in the biochemical deficiency state.
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Methylmalonic aciduria was present.
      explanation: >-
        The case series documents methylmalonic aciduria as a positive
        diagnostic readout of the biochemical cobalamin-deficiency pattern.
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Methylmalonic aciduria was present.
    explanation: >-
      The case series documents methylmalonic aciduria as a biochemical
      consequence of intrinsic factor deficiency.
- name: Homocysteine
  presence: INCREASED
  context: >-
    Hyperhomocysteinemia is a downstream marker of impaired cobalamin-dependent
    one-carbon metabolism.
  biomarker_term:
    preferred_term: homocysteine
    term:
      id: CHEBI:17230
      label: homocysteine
  readouts:
  - target: Biochemical cobalamin deficiency pattern
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Elevated homocysteine reports impaired cobalamin-dependent one-carbon
      metabolism in the biochemical deficiency state.
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Homocysteine was high at 16.7 (5.0-12.0 umol/L).
      explanation: >-
        The reported hyperhomocysteinemia supports homocysteine as a positive
        diagnostic readout of the biochemical cobalamin-deficiency pattern.
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Homocysteine was high at 16.7 (5.0-12.0 umol/L).
    explanation: >-
      The reported elevated homocysteine supports abnormal cobalamin-dependent
      one-carbon metabolism.
genetic:
- name: CBLIF/GIF pathogenic variants
  gene_term:
    preferred_term: CBLIF
    term:
      id: hgnc:4268
      label: CBLIF
  inheritance:
  - name: Autosomal recessive
    evidence:
    - reference: DOI:10.1073/pnas.0500517102
      reference_title: "Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The gastric IF (
                            GIF
                            ) gene located in this region harbored homozygous nonsense and missense mutations in these four families and in three additional families.
      explanation: >-
        Homozygous GIF variants in affected families support autosomal recessive
        inheritance.
  variants:
  - name: c.183_186delGAAT
    description: >-
      Four-base deletion in the intrinsic factor gene reported in inherited
      intrinsic factor deficiency, predicted to cause premature termination.
    evidence:
    - reference: DOI:10.1182/blood-2003-07-2239
      reference_title: "Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        the nucleotide sequence analysis identified a 4-base deletion (c183_186delGAAT) spanning positions 104 to 107 in exon 2, resulting in premature termination of translation.
      explanation: >-
        This abstract directly supports the variant and its predicted
        loss-of-function consequence.
  - name: c.776delA and c.585C>A
    description: >-
      Compound heterozygous frameshift and nonsense variants reported in an East
      Asian patient with hereditary intrinsic factor deficiency.
    evidence:
    - reference: DOI:10.1186/s12881-020-01158-z
      reference_title: "Hereditary intrinsic factor deficiency in China caused by a novel mutation in the intrinsic factor gene—a case report"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Gene test verified a c.776delA frame shift mutation in exon 6 combined with c.585C > A nonsense early termination mutation in exon 5 of GIF which result in the dysfunction of gastric intrinsic factor protein.
      explanation: >-
        This case report supports compound heterozygous loss-of-function GIF
        variation as a disease mechanism.
  - name: c.79+1G>A and c.973delG
    description: >-
      Compound heterozygous splice-site and deletion variants reported in Old
      Order Mennonite individuals with gastric intrinsic factor deficiency.
    evidence:
    - reference: PMID:25308559
      reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Mutation analysis of GIF revealed compound heterozygosity for
        a c.79+1G>A substitution and a c.973delG deletion in all three individuals.
      explanation: >-
        This case series supports the Mennonite compound heterozygous GIF
        variant pattern highlighted by the reviewer.
  features: >-
    Disease-causing variants in CBLIF/GIF include nonsense, missense,
    frameshift, and splice-disrupting alleles that impair gastric intrinsic
    factor production or function.
  evidence:
  - reference: PMID:22929189
    reference_title: "Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified mutations in 126/154 unrelated cases (82%). Fifty-three of 126 cases
      (42%) were mutated in CUBN, 45/126 (36%) were mutated in AMN, and 28/126 (22%)
      had mutations in GIF.
    explanation: >-
      The large molecular screening cohort supports GIF as one of the three
      causal genes for inherited cobalamin malabsorption.
diagnosis:
- name: Molecular testing for inherited cobalamin malabsorption genes
  description: >-
    Molecular testing of CBLIF/GIF together with CUBN and AMN distinguishes
    hereditary intrinsic factor deficiency from Imerslund-Gräsbeck syndrome and
    other inherited cobalamin malabsorption disorders.
  evidence:
  - reference: DOI:10.1073/pnas.0500517102
    reference_title: "Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In the diagnosis of juvenile cobalamin deficiency, mutational analysis of the
                          CUBN
                          ,
                          AMN
                          , and
                          GIF
                          genes provides a molecular characterization of the underlying defect and may be the diagnostic method of choice.
    explanation: >-
      The family study recommends molecular testing across CUBN, AMN, and GIF as
      a diagnostic strategy for juvenile cobalamin deficiency.
- name: Vitamin B12 absorption testing with intrinsic factor
  description: >-
    Historical absorption testing can show correction of cobalamin absorption
    after intrinsic factor coadministration, supporting intrinsic-factor-related
    malabsorption.
  evidence:
  - reference: DOI:10.1182/blood-2003-07-2239
    reference_title: "Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The bone marrow showed frank megaloblastic morphology, and the Schilling test indicated a failure to absorb Cbl that was corrected by coadministration of IF.
    explanation: >-
      The reported Schilling-test correction supports an absorption assay
      pattern specific to intrinsic factor deficiency.
  - reference: clinicaltrials:NCT00279552
    reference_title: "Can Recombinant Human Intrinsic Factor Be Used for Evaluation of the Vitamin B12 Absorption?"
    supports: PARTIAL
    snippet: >-
      The purpose of this study was to examine whether recombinant human intrinsic factor is able to promote the uptake of vitamin B12 in patients with evident vitamin B12 deficiency.
    explanation: >-
      The trial summary supports recombinant intrinsic factor as a diagnostic
      adjunct concept for evaluating vitamin B12 absorption, but it is not
      specific to hereditary intrinsic factor deficiency.
treatments:
- name: Lifelong vitamin B12 replacement
  description: >-
    Lifelong vitamin B12 replacement bypasses defective intrinsic factor
    availability and prevents or reverses hematologic and biochemical
    consequences of cobalamin malabsorption. Published cases include response
    to oral as well as parenteral vitamin B12, consistent with the treatment
    bypassing intrinsic factor-dependent absorption when sufficiently dosed.
  treatment_term:
    preferred_term: vitamin supplementation
    term:
      id: MAXO:0001129
      label: vitamin supplementation
    therapeutic_agent:
    - preferred_term: hydroxocobalamin
      term:
        id: CHEBI:27786
        label: hydroxocobalamin
  target_mechanisms:
  - target: Impaired intrinsic factor-dependent cobalamin absorption
    treatment_effect: BYPASSES
    description: >-
      Pharmacologic vitamin B12 replacement bypasses the defective
      intrinsic-factor-dependent absorption step, especially when delivered
      parenterally.
    evidence:
    - reference: PMID:22854512
      reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Accurate diagnosis is always an emergency because early detection and treatment with life-long parenteral pharmacological doses of hydroxocobalamin are life saving and prevent further deterioration.
      explanation: >-
        The cobalamin-absorption-disorder cohort supports parenteral
        hydroxocobalamin as a disease-modifying route that bypasses the
        absorption defect.
  - target: Biochemical cobalamin deficiency pattern
    treatment_effect: RESTORES
    description: >-
      Vitamin B12 replacement restores cobalamin availability and normalizes
      hematologic and metabolic markers with appropriate follow-up.
    evidence:
    - reference: PMID:22854512
      reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Unlike previous recommendations, we showed that a maintenance dosage of 1 mg cobalamin
        twice a year was enough to ensure a normal clinical status and keep the
        hematological and metabolic parameters in the normal range.
      explanation: >-
        The maintenance-therapy cohort supports cobalamin replacement as
        sufficient to maintain normal clinical, hematologic, and metabolic
        parameters in inherited B12 absorption disorders.
  - target: Megaloblastic erythropoietic failure
    treatment_effect: RESTORES
    description: >-
      Vitamin B12 replacement restores hematologic output when anemia is driven
      by inherited intrinsic factor deficiency.
    evidence:
    - reference: DOI:10.1186/s12881-020-01158-z
      reference_title: "Hereditary intrinsic factor deficiency in China caused by a novel mutation in the intrinsic factor gene—a case report"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The hemoglobin level normalized each time after intramuscular vitamin B12 injection.
      explanation: >-
        This HIFD case report supports vitamin B12 replacement as restoring the
        downstream anemia caused by cobalamin malabsorption.
  evidence:
  - reference: PMID:25308559
    reference_title: "Biochemical and Hematologic Manifestations of Gastric Intrinsic Factor (GIF) Deficiency: A Treatable Cause of B12 Deficiency in the Old Order Mennonite Population of Southwestern Ontario."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Oral or parenteral vitamin B12 has led to complete recovery of clinical parameters
      and vitamin B12 levels.
    explanation: >-
      The GIF-deficiency case series supports vitamin B12 replacement as an
      effective treatment.
  - reference: PMID:22854512
    reference_title: "How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Accurate diagnosis is always an emergency because early detection and treatment with life-long parenteral pharmacological doses of hydroxocobalamin are life saving and prevent further deterioration.
    explanation: >-
      The inherited absorption-disorder treatment cohort supports lifelong
      parenteral hydroxocobalamin as disease-modifying therapy.
differential_diagnoses:
- name: Imerslund-Gräsbeck syndrome
  disease_term:
    preferred_term: Imerslund-Gräsbeck syndrome
  description: >-
    Imerslund-Gräsbeck syndrome causes inherited cobalamin malabsorption through
    CUBN or AMN receptor defects rather than intrinsic factor deficiency.
  distinguishing_features:
  - Proteinuria is typical of Imerslund-Gräsbeck syndrome and is usually absent in intrinsic factor deficiency.
  - Receptor-gene defects in CUBN or AMN distinguish IGS from CBLIF/GIF-related intrinsic factor deficiency.
  evidence:
  - reference: PMID:22929189
    reference_title: "Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      IGS and IFD differ in that IGS usually
      presents with proteinuria, which is not observed in IFD.
    explanation: >-
      The hereditary cobalamin malabsorption cohort directly supports
      proteinuria as a distinguishing feature between IGS and intrinsic factor
      deficiency.

📚

References & Deep Research

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 31 citations 2026-05-14T14:44:34.544118

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Hereditary intrinsic factor deficiency
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Hereditary intrinsic factor deficiency covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Research Report: Hereditary intrinsic factor deficiency (HIFD)

Executive summary

Hereditary intrinsic factor deficiency (HIFD; also called congenital intrinsic factor deficiency, inherited intrinsic factor deficiency, or hereditary juvenile cobalamin deficiency due to GIF) is a rare autosomal recessive disorder of selective vitamin B12 (cobalamin) malabsorption caused by biallelic pathogenic variants in GIF (gastric intrinsic factor). Loss of intrinsic factor (IF) prevents formation of the IF–B12 complex needed for ileal uptake via the cubam receptor (CUBN/AMN), leading to low serum B12, typically elevated methylmalonic acid (MMA) and homocysteine, and childhood-onset macrocytic/megaloblastic anemia with variable neurologic complications; the disease is highly treatable with lifelong B12 replacement. (tanner2012inheritedcobalaminmalabsorption. pages 1-2, mucha2024vitaminb12metabolism pages 3-4, ferrand2015biochemicalandhematologic pages 3-5)

1. Disease information

1.1 Definition and current understanding

HIFD is an inherited disorder of vitamin B12 absorption caused by absent or dysfunctional gastric intrinsic factor due to GIF mutations, presenting most commonly as juvenile-onset B12 deficiency and megaloblastic anemia. (ruan2020hereditaryintrinsicfactor pages 1-2, tanner2005hereditaryjuvenilecobalamin pages 1-2)

1.2 Key identifiers and ontology cross-references

OMIM disease: Intrinsic factor deficiency #261000 (explicitly referenced in case-series literature). (ferrand2015biochemicalandhematologic pages 1-3)
Causal gene: GIF (intrinsic factor; gastric intrinsic factor). (tanner2005hereditaryjuvenilecobalamin pages 2-3)
MONDO / Orphanet / MeSH / ICD-10/ICD-11: Not retrievable from the currently available tool context; should be added by direct lookup in MONDO/Orphanet/MeSH/WHO ICD resources outside this run.

1.3 Synonyms / alternative names

Hereditary intrinsic factor deficiency (HIFD) (sturm2013hereditaryintrinsicfactor pages 2-4)
Congenital intrinsic factor deficiency (gordon2004ageneticpolymorphism pages 5-7)
Inherited intrinsic factor deficiency (yassin2004identificationofa pages 2-3)
Hereditary juvenile cobalamin deficiency; congenital/juvenile pernicious anemia due to GIF (tanner2005hereditaryjuvenilecobalamin pages 2-3)

1.4 Evidence type

The disease characterization is largely derived from case reports/series and a large genetic screening cohort of suspected hereditary cobalamin malabsorption, i.e., aggregated disease-level evidence synthesized from multiple patients rather than EHR-only data. (tanner2012inheritedcobalaminmalabsorption. pages 1-2, ferrand2015biochemicalandhematologic pages 3-5)

2. Etiology

2.1 Primary causal factors

Genetic: Biallelic pathogenic variants in GIF cause intrinsic factor deficiency and thus IF-dependent cobalamin malabsorption. (tanner2005hereditaryjuvenilecobalamin pages 2-3, yassin2004identificationofa pages 2-3)
Mechanistic: Failure to produce functional IF prevents IF–B12 complex formation and thereby blocks cubam-mediated uptake in the terminal ileum. (mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53)

2.2 Risk factors

Family history / consanguinity / founder ancestry: Multiple founder mutations have been described in specific ancestries (e.g., Chaldean/Iraqi founder intronic variant), so ancestry can be a practical risk stratifier for targeted testing. (sturm2013hereditaryintrinsicfactor pages 2-4)

2.3 Protective factors

No genetic or environmental protective factors specific to HIFD were identified in the retrieved evidence.

2.4 Gene–environment interactions

No specific gene–environment interaction evidence (beyond general B12 nutritional status considerations) was identified for HIFD in the retrieved sources.

3. Phenotypes

3.1 Core phenotype spectrum (human)

Typical onset is in infancy/early childhood; symptoms may be delayed because infants may be partially protected by maternal hepatic B12 stores. (ferrand2015biochemicalandhematologic pages 5-6)

Commonly reported features: - Macrocytic/megaloblastic anemia (often severe) (ruan2020hereditaryintrinsicfactor pages 1-2) - Pancytopenia can occur (ferrand2015biochemicalandhematologic pages 1-3) - Gastrointestinal symptoms, pallor, listlessness; possible failure to thrive (ferrand2015biochemicalandhematologic pages 1-3, tanner2005hereditaryjuvenilecobalamin pages 1-2) - Neurologic findings are variable; examples in case series include difficulty walking and paresthesias, and reviews/case discussions note risk of developmental delay and neurocognitive manifestations if untreated. (ferrand2015biochemicalandhematologic pages 1-3, ruan2020hereditaryintrinsicfactor pages 1-2) - Organomegaly (mild splenomegaly/hepatomegaly) reported in some patients. (ruan2020hereditaryintrinsicfactor pages 1-2, ferrand2015biochemicalandhematologic pages 1-3) - Proteinuria: typically absent in HIFD cohorts/cases and can help differentiate from Imerslund–Gräsbeck syndrome (IGS), although it is not perfectly specific. (ferrand2015biochemicalandhematologic pages 3-5, sturm2013hereditaryintrinsicfactor pages 2-4)

3.2 Recent statistics/data points from case-based studies

Examples of reported quantitative clinical/lab findings: - Serum B12 61 pmol/L (ref 198–615), homocysteine 16.7 µmol/L (ref 5–12), and elevated urine MMA in Mennonite cases; normalization after treatment. (ferrand2015biochemicalandhematologic pages 1-3, ferrand2015biochemicalandhematologic pages 3-5) - Macrocytosis and severe anemia improved with therapy (e.g., hemoglobin 72 g/L to 132 g/L; MCV 111 fL to 78.3 fL). (ferrand2015biochemicalandhematologic pages 3-5) - Chinese case: hemoglobin 57 g/L, serum cobalamin 80 pg/mL, LDH 1832 U/L, indirect bilirubin 43.0 µmol/L. (ruan2020hereditaryintrinsicfactor pages 1-2)

3.3 HPO term suggestions (non-exhaustive)

Based on the described phenotypes: - Megaloblastic anemia HP:0001891 - Macrocytosis HP:0001974 - Vitamin B12 deficiency HP:0002659 - Pancytopenia HP:0001876 - Failure to thrive HP:0001508 - Peripheral neuropathy HP:0009830 / Paresthesia HP:0003401 - Developmental delay HP:0001263 - Splenomegaly HP:0001744

(Phenotype presence supported by primary reports, though exact HPO IDs are suggested mappings.) (ferrand2015biochemicalandhematologic pages 1-3, ferrand2015biochemicalandhematologic pages 3-5)

3.4 Quality of life impact

Quality of life burden is primarily through recurrent anemia symptoms, need for lifelong therapy, and risk of irreversible neurologic injury if diagnosis/treatment is delayed. (abdallah2012howcancobalamin pages 1-2, tanner2005hereditaryjuvenilecobalamin pages 1-2)

4. Genetic / molecular information

4.1 Causal gene

GIF encodes intrinsic factor (IF), secreted by gastric parietal cells and required for intestinal B12 absorption. (tanner2005hereditaryjuvenilecobalamin pages 2-3)

4.2 Variant spectrum (examples)

Variant classes include frameshift, nonsense, splice-site, and missense variants: - Frameshift: exon 2 deletion c.183_186delGAAT predicted to truncate IF; no immunoreactive IF in gastric juice. (Publication date Feb 2004; URL https://doi.org/10.1182/blood-2003-07-2239) (yassin2004identificationofa pages 2-3) - Compound heterozygous: c.79+1G>A (splice) and c.973delG (frameshift) in Old Order Mennonite families. (Publication date Jan 2015; URL https://doi.org/10.1007/8904_2014_351) (ferrand2015biochemicalandhematologic pages 1-3, ferrand2015biochemicalandhematologic pages 3-5) - Founder intronic variant: c.1073+5G>A reported as a Chaldean/Iraqi founder mutation. (Publication date Jan 2013; URL https://doi.org/10.1007/8904_2012_133) (sturm2013hereditaryintrinsicfactor pages 2-4) - East Asian compound heterozygous variants (first reported East Asia): c.776delA and c.585C>A. (Publication date Nov 2020; URL https://doi.org/10.1186/s12881-020-01158-z) (ruan2020hereditaryintrinsicfactor pages 1-2)

4.3 Functional consequence

Most disease-causing variants are consistent with loss of function (absent or dysfunctional IF), leading to failure of IF-dependent B12 absorption. (yassin2004identificationofa pages 2-3, ruan2020hereditaryintrinsicfactor pages 1-2)

4.4 Modifier genes / epigenetics / chromosomal abnormalities

No validated modifier genes, epigenetic mechanisms, or chromosomal abnormalities specific to HIFD were identified in the retrieved evidence.

5. Environmental information

HIFD is primarily genetic; environmental factors mainly influence overall B12 status rather than disease causation. No specific toxins, lifestyle drivers, or infectious triggers were identified as causal for HIFD in the retrieved sources.

6. Mechanism / pathophysiology

6.1 Causal chain (upstream → downstream)

Biallelic GIF variants → loss of intrinsic factor production/function. (tanner2005hereditaryjuvenilecobalamin pages 2-3, yassin2004identificationofa pages 2-3)
Failure to form the IF–B12 complex in the intestinal lumen. (mucha2024vitaminb12metabolism pages 3-4)
Failure of receptor-mediated uptake of IF–B12 by cubam (CUBN/AMN) on ileal enterocytes. (mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53)
Systemic B12 deficiency → biochemical hallmarks: elevated MMA and homocysteine. (ferrand2015biochemicalandhematologic pages 1-3, mucha2024vitaminb12metabolism pages 3-4)
Downstream clinical effects: ineffective erythropoiesis/megaloblastic anemia and neurologic injury risk. (ferrand2015biochemicalandhematologic pages 3-5, tanner2005hereditaryjuvenilecobalamin pages 1-2)

6.2 Molecular pathways and GO/CL suggestions

Suggested GO Biological Process terms:
Cobalamin metabolic process (GO:0009236)
Vitamin transport (GO:0051180)
One-carbon metabolic process (GO:0006730) (downstream effect)
Erythrocyte differentiation / hematopoiesis processes relevant to megaloblastic anemia
Suggested Cell Ontology (CL) terms:
Gastric parietal cell (IF production)
Enterocyte (ileal uptake)
Erythroblast / hematopoietic stem and progenitor cell (bone marrow phenotype)

(These are ontology suggestions grounded in the mechanistic descriptions and affected tissues.) (mucha2024vitaminb12metabolism media 55829a53, ferrand2015biochemicalandhematologic pages 3-5)

6.3 Visual evidence (2024 schematic)

A 2024 review provides a figure summarizing IF-dependent B12 absorption and downstream trafficking steps (IF–B12 complex, cubam receptor uptake, and intracellular handling). (Publication date Jul 2024; URL https://doi.org/10.3390/ijms25158021) (mucha2024vitaminb12metabolism media 55829a53)

7. Anatomical structures affected

Organ/tissue levels (UBERON suggestions)

Stomach (gastric mucosa)—parietal cells secrete IF; in HIFD the mucosa is generally normal but IF protein is deficient. (UBERON:0000945 stomach; UBERON:0001155 gastric mucosa) (ferrand2015biochemicalandhematologic pages 5-6, yassin2004identificationofa pages 2-3)
Terminal ileum / small intestine—site of IF–B12 uptake via cubam. (UBERON:0002116 ileum) (mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53)
Bone marrow—megaloblastic erythroid hyperplasia/ineffective erythropoiesis. (UBERON:0002371 bone marrow) (ruan2020hereditaryintrinsicfactor pages 1-2)
Peripheral nervous system / spinal cord—neurologic complications possible if untreated. (tanner2005hereditaryjuvenilecobalamin pages 1-2, ruan2020hereditaryintrinsicfactor pages 1-2)

8. Temporal development

Onset: typically pediatric; cases diagnosed as early as ~18 months and commonly in early childhood; symptoms may be delayed by maternal stores. (sturm2013hereditaryintrinsicfactor pages 2-4, ferrand2015biochemicalandhematologic pages 5-6)
Course: chronic/lifelong unless treated; hematologic abnormalities respond rapidly to replacement, but delayed diagnosis can permit progressive neurologic injury. (abdallah2012howcancobalamin pages 1-2, tanner2005hereditaryjuvenilecobalamin pages 1-2)

9. Inheritance and population

Inheritance: autosomal recessive with affected individuals carrying biallelic GIF variants and parents typically heterozygous carriers. (tanner2005hereditaryjuvenilecobalamin pages 2-3, gordon2004ageneticpolymorphism pages 5-7)
Population/founder effects: documented founder mutation in Chaldeans from Iraq; clustering in Old Order Mennonite population; founder mutation described in individuals of African ancestry; first genetically confirmed East Asian case reported in 2020. (sturm2013hereditaryintrinsicfactor pages 2-4, ferrand2015biochemicalandhematologic pages 1-3, ruan2020hereditaryintrinsicfactor pages 1-2)
Epidemiology statistics: robust prevalence/incidence data were not available in the retrieved sources. A large genetic screening study of suspected hereditary cobalamin malabsorption found that among genetically solved cases, GIF accounted for 28/126 (22%) of cases, while CUBN was 42% and AMN 36%. (Publication date Aug 2012; URL https://doi.org/10.1186/1750-1172-7-56) (tanner2012inheritedcobalaminmalabsorption. pages 1-2)

10. Diagnostics

10.1 Clinical tests and biomarkers

CBC with macrocytosis/megaloblastic anemia; consider pancytopenia. (ferrand2015biochemicalandhematologic pages 1-3)
Serum cobalamin (low) and metabolic markers: MMA and homocysteine are commonly elevated; MMA can be detected in urine organic acids. (ferrand2015biochemicalandhematologic pages 1-3, ferrand2015biochemicalandhematologic pages 3-5)
Assess proteinuria to help differentiate from IGS (often present in IGS, usually absent in HIFD). (ferrand2015biochemicalandhematologic pages 3-5, sturm2013hereditaryintrinsicfactor pages 2-4)

10.2 Functional absorption testing

Historical Schilling/radiocobalamin absorption testing: repeat with added intrinsic factor can distinguish intrinsic-factor-related malabsorption (corrects with IF) from receptor defects; however, the test is often unavailable/obsolete. (grasbeck2006imerslundgräsbecksyndrome(selective pages 3-5, ruan2020hereditaryintrinsicfactor pages 2-4)

10.3 Autoimmune evaluation / differential diagnosis

Test for intrinsic factor antibodies / parietal cell antibodies to distinguish autoimmune pernicious anemia from hereditary GIF deficiency; HIFD should lack intrinsic factor antibodies and may have normal gastroscopy. (ruan2020hereditaryintrinsicfactor pages 2-4, ruan2020hereditaryintrinsicfactor pages 1-2)

10.4 Genetic testing approach

Given heterogeneity of hereditary cobalamin malabsorption, several authoritative sources recommend sequencing GIF plus CUBN and AMN (and other B12-handling genes where indicated) as the preferred modern diagnostic strategy as functional radiocobalamin tests become impractical. (tanner2005hereditaryjuvenilecobalamin pages 1-2, ferrand2015biochemicalandhematologic pages 1-3)

10.5 Differential diagnosis (non-exhaustive)

Imerslund–Gräsbeck syndrome (CUBN/AMN; often proteinuria) (ferrand2015biochemicalandhematologic pages 3-5)
Autoimmune pernicious anemia (anti-IF/parietal cell antibodies) (grasbeck2006imerslundgräsbecksyndrome(selective pages 3-5)
Transcobalamin deficiency and intracellular cobalamin defects (may be suggested by newborn screening markers such as C3, though GIF cases can have normal newborn screening) (ferrand2015biochemicalandhematologic pages 5-6)

11. Outcome / prognosis

With appropriate replacement therapy, case series report complete clinical/biochemical recovery and normal development, whereas untreated disease can be fatal and/or lead to persistent neurologic deficits. (ferrand2015biochemicalandhematologic pages 3-5, tanner2005hereditaryjuvenilecobalamin pages 1-2)

12. Treatment

12.1 Standard of care: vitamin B12 replacement

Lifelong parenteral B12 is widely used; example regimens include monthly hydroxocobalamin 1,000 mcg and acute repletion (e.g., 0.5 mg every other day in one case). (sturm2013hereditaryintrinsicfactor pages 2-4, ruan2020hereditaryintrinsicfactor pages 1-2)
Evidence for extended maintenance intervals: in a small series of inborn errors of B12 absorption (including HIFD/IGS), 1 mg every 6 months maintained normal clinical, hematologic, and metabolic parameters with follow-up. (Publication date Sep 2012; URL https://doi.org/10.1016/j.ymgme.2012.07.007) (abdallah2012howcancobalamin pages 1-2)
Oral B12 can be effective in GIF deficiency because gastric mucosa is normal; Mennonite series explicitly notes response to oral supplementation and symptom avoidance with early diagnosis. (ferrand2015biochemicalandhematologic pages 5-6, ferrand2015biochemicalandhematologic pages 3-5)

MAXO term suggestions - Vitamin B12 supplementation therapy (parenteral) (MAXO: medical action—parenteral vitamin supplementation) - Vitamin B12 supplementation therapy (oral high-dose) - Genetic testing / molecular diagnosis (MAXO: genetic test)

12.2 Real-world implementation: recombinant intrinsic factor as diagnostic tool

A completed phase 2 trial evaluated recombinant human intrinsic factor as a diagnostic adjunct to assess vitamin B12 absorption using holotranscobalamin response, motivated by limitations of the Schilling test and limited access to native intrinsic factor reagent. (ClinicalTrials.gov NCT00279552; University of Aarhus; publication year listed 2004) (NCT00279552 chunk 1)

13. Prevention

Primary prevention of disease onset is not applicable for an autosomal recessive congenital disorder, but secondary/tertiary prevention is crucial: - Early detection in at-risk families (cascade testing) and prompt B12 treatment to prevent irreversible neurologic injury. (abdallah2012howcancobalamin pages 1-2, tanner2005hereditaryjuvenilecobalamin pages 1-2)

14–15. Other species / model organisms

No HIFD-specific natural animal disease evidence was retrieved in this run. (Note: there are mouse models involving Gif deficiency in broader literature, but detailed evidence was not extracted here.)

Recent developments and expert analysis (2023–2024 emphasis)

A 2024 authoritative review synthesized current understanding of B12 absorption and intracellular handling as a multi-protein network, explicitly detailing IF binding, cubam receptor uptake, and downstream trafficking proteins; this provides the most up-to-date mechanistic framework supporting HIFD pathophysiology and diagnostic marker interpretation. (Publication date Jul 2024; URL https://doi.org/10.3390/ijms25158021) (mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53)

Structured evidence table

Category	Key facts	Supporting evidence
Definition	Hereditary intrinsic factor deficiency (IFD), also called congenital intrinsic factor deficiency or hereditary juvenile cobalamin deficiency due to GIF, is a rare inherited disorder of selective vitamin B12 absorption caused by absent/dysfunctional gastric intrinsic factor, leading to cobalamin deficiency and typically megaloblastic anemia in childhood.	OMIM noted as #261000 in case literature; defined as a rare inherited cause of B12 deficiency due to GIF mutations (ferrand2015biochemicalandhematologic pages 1-3, ruan2020hereditaryintrinsicfactor pages 1-2). PNAS 2005 established GIF mutations as cause of hereditary juvenile cobalamin deficiency: DOI https://doi.org/10.1073/pnas.0500517102 (tanner2005hereditaryjuvenilecobalamin pages 1-2, tanner2005hereditaryjuvenilecobalamin pages 2-3). Blood 2004 first molecular proof of inherited IF deficiency: DOI https://doi.org/10.1182/blood-2003-07-2239 (yassin2004identificationofa pages 2-3).
Gene / inheritance	Causal gene: GIF (gastric intrinsic factor gene; chromosome 11q12). Inheritance is autosomal recessive; affected patients generally have biallelic pathogenic variants, while parents are heterozygous carriers.	“all patients … were homozygous, whereas their respective parents were heterozygous,” supporting AR inheritance (PNAS 2005; DOI https://doi.org/10.1073/pnas.0500517102) (tanner2005hereditaryjuvenilecobalamin pages 2-3). Ruan 2020 reports compound heterozygous c.776delA and c.585C>A in a Chinese patient (DOI https://doi.org/10.1186/s12881-020-01158-z) (ruan2020hereditaryintrinsicfactor pages 1-2). Ferrand 2015 reports compound heterozygosity c.79+1G>A and c.973delG (DOI https://doi.org/10.1007/8904_2014_351) (ferrand2015biochemicalandhematologic pages 1-3).
Core mechanism	Normal physiology: intrinsic factor (IF), secreted by gastric parietal cells, binds vitamin B12 after haptocorrin degradation in the duodenum; the IF–B12 complex is absorbed in the ileum through the cubam receptor composed of cubilin (CUBN) and amnionless (AMN). In GIF deficiency, lack of functional IF prevents IF–B12 complex formation and causes selective intestinal B12 malabsorption.	GIF encodes IF, “a 417-aa protein secreted by gastric parietal cells that binds cobalamin” (PNAS 2005; DOI https://doi.org/10.1073/pnas.0500517102) (tanner2005hereditaryjuvenilecobalamin pages 2-3). 2024 review summarizes that only the IF–vitamin B12 complex is recognized by cubam on ileal enterocytes; cubam consists of CUBN + AMN (DOI https://doi.org/10.3390/ijms25158021) (mucha2024vitaminb12metabolism pages 4-6, mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53).
Typical onset / natural history	Usually presents in infancy or early childhood; recurrent or progressive anemia is common. Untreated disease may cause failure to thrive, neurologic injury, and can be fatal, but prognosis is excellent with timely lifelong B12 replacement.	Ferrand 2015: congenital IFD “presents in infancy or early childhood” with low serum cobalamin and megaloblastic anemia (DOI https://doi.org/10.1007/8904_2014_351) (ferrand2015biochemicalandhematologic pages 1-3). Ruan 2020 case had recurrent severe anemia from age 2 (DOI https://doi.org/10.1186/s12881-020-01158-z) (ruan2020hereditaryintrinsicfactor pages 1-2). PNAS 2005 notes inherited cobalamin malabsorption can be fatal untreated (DOI https://doi.org/10.1073/pnas.0500517102) (tanner2005hereditaryjuvenilecobalamin pages 1-2).
Key phenotypes	Hallmark phenotype is megaloblastic/macrocytic anemia. Other reported features: pancytopenia, weakness/fatigue, jaundice, failure to thrive, feeding/GI symptoms, hepatosplenomegaly, peripheral neuropathy, and variable neurologic manifestations.	Macrocytosis example MCV 111.6 fL and very low B12 in Chaldean cases (JIMD Rep 2013; DOI https://doi.org/10.1007/8904_2012_133) (sturm2013hereditaryintrinsicfactor pages 1-2). Ferrand 2015 lists pancytopenia, splenomegaly, hepatomegaly, peripheral neuropathy, GI symptoms, infantile death (ferrand2015biochemicalandhematologic pages 1-3). Ruan 2020 notes severity ranging from weakness to life-threatening anemia, jaundice, and neurologic abnormalities (ruan2020hereditaryintrinsicfactor pages 1-2).
Diagnostic biomarkers / tests	Typical lab pattern: low serum vitamin B12, often elevated methylmalonic acid (MMA) and elevated homocysteine; macrocytosis/megaloblastic marrow and sometimes elevated C3/acylcarnitine-related markers. Historical functional test: Schilling/radiocobalamin absorption. Genetic confirmation by GIF sequencing is now preferred.	Ferrand 2015 example: serum B12 61 pmol/L (ref 198–615), homocysteine 16.7 µmol/L, methylmalonic aciduria, elevated C3 (DOI https://doi.org/10.1007/8904_2014_351) (ferrand2015biochemicalandhematologic pages 1-3). 2024 review: impaired B12 metabolism raises MMA and homocysteine, important diagnostic markers (DOI https://doi.org/10.3390/ijms25158021) (mucha2024vitaminb12metabolism pages 3-4). Tanner 2012 recommends low serum Cbl plus elevated homocysteine/MMA and molecular analysis of CUBN, AMN, GIF; Schilling test has been retired (DOI https://doi.org/10.1186/1750-1172-7-56) (tanner2012inheritedcobalaminmalabsorption. pages 1-2).
Distinguishing from Imerslund–Gräsbeck syndrome (IGS)	IFD phenocopies IGS hematologically, but proteinuria is usually absent in IFD and common in IGS. Historically, low B12 absorption in IFD is corrected by added intrinsic factor on radiocobalamin testing, whereas IGS is not corrected because the cubam receptor is defective.	Tanner 2012: IGS usually presents with proteinuria, “which is not observed in IFD” (DOI https://doi.org/10.1186/1750-1172-7-56) (tanner2012inheritedcobalaminmalabsorption. pages 1-2). PNAS 2005: inherited IFD should be distinguished from IGS because radiocobalamin absorption with IF corrects low absorption in IFD (tanner2005hereditaryjuvenilecobalamin pages 2-3). JIMD 2013 case emphasized absence of proteinuria and lack of Schilling response details for IFD workup (sturm2013hereditaryintrinsicfactor pages 1-2).
Gastric / autoimmune findings	Unlike autoimmune pernicious anemia, hereditary IFD usually has normal gastroscopy/gastric acid secretion and negative intrinsic-factor antibodies.	Ruan 2020: patients “usually present with cobalamin deficiency without gastroscopy abnormality and intrinsic factor antibodies” (DOI https://doi.org/10.1186/s12881-020-01158-z) (ruan2020hereditaryintrinsicfactor pages 2-4, ruan2020hereditaryintrinsicfactor pages 1-2). Yassin 2004 documented normal gastric acid output despite severe IF deficiency (DOI https://doi.org/10.1182/blood-2003-07-2239) (yassin2004identificationofa pages 2-3).
Treatment / real-world management	Standard care is lifelong vitamin B12 replacement, usually parenteral hydroxocobalamin or cyanocobalamin. Hematologic and biochemical response is typically rapid and robust; early treatment helps prevent irreversible neurologic sequelae. Some reports describe successful oral therapy in selected patients, but IM therapy remains standard.	Ruan 2020: intramuscular vitamin B12 normalized hemoglobin; example initial dosing 0.5 mg every other day (ruan2020hereditaryintrinsicfactor pages 1-2). Sturm 2013: monthly hydroxocobalamin 1,000 mcg resolved clinical issues (sturm2013hereditaryintrinsicfactor pages 1-2). Abdallah 2012: life-long parenteral Cbl is lifesaving; in 7 patients, 1 mg twice yearly maintained normal clinical, hematologic, and metabolic parameters after stabilization (DOI https://doi.org/10.1016/j.ymgme.2012.07.007) (abdallah2012howcancobalamin pages 1-2). Ferrand 2015: oral or parenteral B12 led to complete recovery (ferrand2015biochemicalandhematologic pages 1-3).
Prognosis	With prompt recognition and replacement therapy, patients can remain healthy long term; delay risks persistent neurologic damage.	Tanner 2012: “Early diagnosis improves the lifelong care required by these patients and prevents potential neurological long-term complications” (abstract summarized in evidence) (DOI https://doi.org/10.1186/1750-1172-7-56) (tanner2012inheritedcobalaminmalabsorption. pages 1-2). Abdallah 2012 and multiple case reports show durable normalization under maintenance B12 (abdallah2012howcancobalamin pages 1-2, ferrand2015biochemicalandhematologic pages 1-3, ruan2020hereditaryintrinsicfactor pages 1-2).
Founder effects / populations	Population-specific founder variants have been reported. Examples include a West-African founder mutation, a Chaldean/Iraqi founder mutation c.1073+5G>A, and a treatable cluster in the Old Order Mennonite population of southwestern Ontario. A 2020 report described the first East Asian genetically confirmed case.	Ament 2009: juvenile cobalamin deficiency in individuals of African ancestry caused by a founder GIF mutation (DOI https://doi.org/10.1111/j.1365-2141.2008.07496.x) (tanner2005hereditaryjuvenilecobalamin pages 1-2, ruan2020hereditaryintrinsicfactor pages 2-4). Sturm 2013: intronic c.1073+5G>A identified as a founder mutation limited to Chaldeans from Iraq (DOI https://doi.org/10.1007/8904_2012_133) (sturm2013hereditaryintrinsicfactor pages 1-2). Ferrand 2015 describes cases in Old Order Mennonites (DOI https://doi.org/10.1007/8904_2014_351) (ferrand2015biochemicalandhematologic pages 1-3). Ruan 2020 reports first East-Asia mutation-defined case (ruan2020hereditaryintrinsicfactor pages 1-2).
Key statistics	In the largest screening study of suspected hereditary cobalamin malabsorption, pathogenic variants were identified in 126/154 unrelated cases (82%). Among solved cases, 28/126 (22%) had GIF mutations; 53/126 (42%) had CUBN and 45/126 (36%) had AMN variants. The study reported 52 novel defects, including 7 novel GIF variants.	Tanner 2012, Orphanet J Rare Dis: 154 families/patients screened; 126 solved (82%); 22% GIF, 42% CUBN, 36% AMN; 52 novel defects total, 7 in GIF (DOI https://doi.org/10.1186/1750-1172-7-56) (tanner2012inheritedcobalaminmalabsorption. pages 1-2).
Recent developments (2023–2024)	No major 2023–2024 disease-specific therapeutic breakthroughs were found; recent progress is mainly in broader B12 pathway reviews and continued use of genetic sequencing for precise diagnosis. Current understanding reinforces IF–cubam biology and biomarker-based diagnosis (B12, MMA, homocysteine).	2024 review provides updated pathway synthesis of IF-dependent absorption and downstream trafficking (DOI https://doi.org/10.3390/ijms25158021) (mucha2024vitaminb12metabolism pages 4-6, mucha2024vitaminb12metabolism pages 3-4, mucha2024vitaminb12metabolism media 55829a53). No disease-specific interventional trials for hereditary IFD were identified in the retrieved trial search; management remains replacement therapy informed by established case series (abdallah2012howcancobalamin pages 1-2).

Table: This table condenses the main definitional, genetic, mechanistic, diagnostic, treatment, and population-genetic facts for hereditary intrinsic factor deficiency due to GIF. It is designed as a quick-reference evidence map with direct links to the supporting literature and available context IDs.

References

(tanner2012inheritedcobalaminmalabsorption. pages 1-2): Stephan M Tanner, Amy C Sturm, Elizabeth C Baack, Sandya Liyanarachchi, and Albert de la Chapelle. Inherited cobalamin malabsorption. mutations in three genes reveal functional and ethnic patterns. Orphanet Journal of Rare Diseases, 7:56-56, Aug 2012. URL: https://doi.org/10.1186/1750-1172-7-56, doi:10.1186/1750-1172-7-56. This article has 72 citations and is from a peer-reviewed journal.
(mucha2024vitaminb12metabolism pages 3-4): Patryk Mucha, Filip Kus, Dominik Cysewski, Ryszard Tomasz Smolenski, and Marta Tomczyk. Vitamin b12 metabolism: a network of multi-protein mediated processes. International Journal of Molecular Sciences, Jul 2024. URL: https://doi.org/10.3390/ijms25158021, doi:10.3390/ijms25158021. This article has 53 citations.
(ferrand2015biochemicalandhematologic pages 3-5): A. Ferrand, V. M. Siu, C. A. Rupar, M. P. Napier, O. Y. Al-Dirbashi, P. Chakraborty, and C. Prasad. Biochemical and hematologic manifestations of gastric intrinsic factor (gif) deficiency: a treatable cause of b12 deficiency in the old order mennonite population of southwestern ontario. JIMD reports, 18:69-77, Jan 2015. URL: https://doi.org/10.1007/8904_2014_351, doi:10.1007/8904_2014_351. This article has 10 citations and is from a peer-reviewed journal.
(ruan2020hereditaryintrinsicfactor pages 1-2): Jing Ruan, Bing Han, Junling Zhuang, Miao Chen, Fangfei Chen, Yuzhou Huang, and Wenzhe Zhou. Hereditary intrinsic factor deficiency in china caused by a novel mutation in the intrinsic factor gene—a case report. BMC Medical Genetics, Nov 2020. URL: https://doi.org/10.1186/s12881-020-01158-z, doi:10.1186/s12881-020-01158-z. This article has 1 citations and is from a peer-reviewed journal.
(tanner2005hereditaryjuvenilecobalamin pages 1-2): Stephan M. Tanner, Zhongyuan Li, James D. Perko, Cihan Öner, Mualla Çetin, Çiğdem Altay, Zekiye Yurtsever, Karen L. David, Laurence Faivre, Essam A. Ismail, Ralph Gräsbeck, and Albert de la Chapelle. Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene. Proceedings of the National Academy of Sciences of the United States of America, 102 11:4130-3, Mar 2005. URL: https://doi.org/10.1073/pnas.0500517102, doi:10.1073/pnas.0500517102. This article has 140 citations and is from a highest quality peer-reviewed journal.
(ferrand2015biochemicalandhematologic pages 1-3): A. Ferrand, V. M. Siu, C. A. Rupar, M. P. Napier, O. Y. Al-Dirbashi, P. Chakraborty, and C. Prasad. Biochemical and hematologic manifestations of gastric intrinsic factor (gif) deficiency: a treatable cause of b12 deficiency in the old order mennonite population of southwestern ontario. JIMD reports, 18:69-77, Jan 2015. URL: https://doi.org/10.1007/8904_2014_351, doi:10.1007/8904_2014_351. This article has 10 citations and is from a peer-reviewed journal.
(tanner2005hereditaryjuvenilecobalamin pages 2-3): Stephan M. Tanner, Zhongyuan Li, James D. Perko, Cihan Öner, Mualla Çetin, Çiğdem Altay, Zekiye Yurtsever, Karen L. David, Laurence Faivre, Essam A. Ismail, Ralph Gräsbeck, and Albert de la Chapelle. Hereditary juvenile cobalamin deficiency caused by mutations in the intrinsic factor gene. Proceedings of the National Academy of Sciences of the United States of America, 102 11:4130-3, Mar 2005. URL: https://doi.org/10.1073/pnas.0500517102, doi:10.1073/pnas.0500517102. This article has 140 citations and is from a highest quality peer-reviewed journal.
(sturm2013hereditaryintrinsicfactor pages 2-4): Amy C. Sturm, Elizabeth C. Baack, Michael B. Armstrong, Deborah Schiff, Ayesha Zia, Sureyya Savasan, Albert de la Chapelle, and Stephan M. Tanner. Hereditary intrinsic factor deficiency in chaldeans. JIMD reports, 7:13-8, Jan 2013. URL: https://doi.org/10.1007/8904_2012_133, doi:10.1007/8904_2012_133. This article has 9 citations and is from a peer-reviewed journal.
(gordon2004ageneticpolymorphism pages 5-7): Marilyn M. Gordon, Nancy Brada, Angel Remacha, Isabel Badell, Elisabeth del Río, Montserrat Baiget, René Santer, Edward V. Quadros, Sheldon P. Rothenberg, and David H. Alpers. A genetic polymorphism in the coding region of the gastric intrinsic factor gene (gif) is associated with congenital intrinsic factor deficiency. Human Mutation, 23:85-91, Jan 2004. URL: https://doi.org/10.1002/humu.10297, doi:10.1002/humu.10297. This article has 42 citations and is from a domain leading peer-reviewed journal.
(yassin2004identificationofa pages 2-3): Fawwaz Yassin, Sheldon P. Rothenberg, Sreedhar Rao, Marilyn M. Gordon, David H. Alpers, and Edward V. Quadros. Identification of a 4-base deletion in the gene in inherited intrinsic factor deficiency. Blood, 103 4:1515-7, Feb 2004. URL: https://doi.org/10.1182/blood-2003-07-2239, doi:10.1182/blood-2003-07-2239. This article has 52 citations and is from a highest quality peer-reviewed journal.
(mucha2024vitaminb12metabolism media 55829a53): Patryk Mucha, Filip Kus, Dominik Cysewski, Ryszard Tomasz Smolenski, and Marta Tomczyk. Vitamin b12 metabolism: a network of multi-protein mediated processes. International Journal of Molecular Sciences, Jul 2024. URL: https://doi.org/10.3390/ijms25158021, doi:10.3390/ijms25158021. This article has 53 citations.
(ferrand2015biochemicalandhematologic pages 5-6): A. Ferrand, V. M. Siu, C. A. Rupar, M. P. Napier, O. Y. Al-Dirbashi, P. Chakraborty, and C. Prasad. Biochemical and hematologic manifestations of gastric intrinsic factor (gif) deficiency: a treatable cause of b12 deficiency in the old order mennonite population of southwestern ontario. JIMD reports, 18:69-77, Jan 2015. URL: https://doi.org/10.1007/8904_2014_351, doi:10.1007/8904_2014_351. This article has 10 citations and is from a peer-reviewed journal.
(abdallah2012howcancobalamin pages 1-2): Amina Boina Abdallah, Hélène Ogier de Baulny, Renata Kozyraki, Sandrine Passemard, Odile Fenneteau, Sophie Lebon, Odile Rigal, Bettina Mesples, Karima Yacouben, Stéphane Giraudier, Jean-François Benoist, and Manuel Schiff. How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin b(12) absorption? Molecular genetics and metabolism, 107 1-2:66-71, Sep 2012. URL: https://doi.org/10.1016/j.ymgme.2012.07.007, doi:10.1016/j.ymgme.2012.07.007. This article has 19 citations and is from a peer-reviewed journal.
(grasbeck2006imerslundgräsbecksyndrome(selective pages 3-5): Ralph Gräsbeck. Imerslund-gräsbeck syndrome (selective vitamin b12 malabsorption with proteinuria). Orphanet Journal of Rare Diseases, 1:17-17, May 2006. URL: https://doi.org/10.1186/1750-1172-1-17, doi:10.1186/1750-1172-1-17. This article has 201 citations and is from a peer-reviewed journal.
(ruan2020hereditaryintrinsicfactor pages 2-4): Jing Ruan, Bing Han, Junling Zhuang, Miao Chen, Fangfei Chen, Yuzhou Huang, and Wenzhe Zhou. Hereditary intrinsic factor deficiency in china caused by a novel mutation in the intrinsic factor gene—a case report. BMC Medical Genetics, Nov 2020. URL: https://doi.org/10.1186/s12881-020-01158-z, doi:10.1186/s12881-020-01158-z. This article has 1 citations and is from a peer-reviewed journal.
(NCT00279552 chunk 1): Can Recombinant Human Intrinsic Factor Be Used for Evaluation of the Vitamin B12 Absorption?. University of Aarhus. 2004. ClinicalTrials.gov Identifier: NCT00279552
(mucha2024vitaminb12metabolism pages 4-6): Patryk Mucha, Filip Kus, Dominik Cysewski, Ryszard Tomasz Smolenski, and Marta Tomczyk. Vitamin b12 metabolism: a network of multi-protein mediated processes. International Journal of Molecular Sciences, Jul 2024. URL: https://doi.org/10.3390/ijms25158021, doi:10.3390/ijms25158021. This article has 53 citations.
(sturm2013hereditaryintrinsicfactor pages 1-2): Amy C. Sturm, Elizabeth C. Baack, Michael B. Armstrong, Deborah Schiff, Ayesha Zia, Sureyya Savasan, Albert de la Chapelle, and Stephan M. Tanner. Hereditary intrinsic factor deficiency in chaldeans. JIMD reports, 7:13-8, Jan 2013. URL: https://doi.org/10.1007/8904_2012_133, doi:10.1007/8904_2012_133. This article has 9 citations and is from a peer-reviewed journal.

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Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

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Research Report: Hereditary intrinsic factor deficiency (HIFD)

Executive summary

1. Disease information

1.1 Definition and current understanding

1.2 Key identifiers and ontology cross-references

1.3 Synonyms / alternative names

1.4 Evidence type

2. Etiology

2.1 Primary causal factors

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

3.1 Core phenotype spectrum (human)

3.2 Recent statistics/data points from case-based studies

3.3 HPO term suggestions (non-exhaustive)

3.4 Quality of life impact

4. Genetic / molecular information

4.1 Causal gene

4.2 Variant spectrum (examples)

4.3 Functional consequence

4.4 Modifier genes / epigenetics / chromosomal abnormalities

5. Environmental information

6. Mechanism / pathophysiology

6.1 Causal chain (upstream → downstream)

6.2 Molecular pathways and GO/CL suggestions

6.3 Visual evidence (2024 schematic)

7. Anatomical structures affected

Organ/tissue levels (UBERON suggestions)

8. Temporal development

9. Inheritance and population

10. Diagnostics

10.1 Clinical tests and biomarkers

10.2 Functional absorption testing

10.3 Autoimmune evaluation / differential diagnosis

10.4 Genetic testing approach

10.5 Differential diagnosis (non-exhaustive)

11. Outcome / prognosis

12. Treatment

12.1 Standard of care: vitamin B12 replacement

12.2 Real-world implementation: recombinant intrinsic factor as diagnostic tool

13. Prevention

14–15. Other species / model organisms

Recent developments and expert analysis (2023–2024 emphasis)

Structured evidence table

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