Biotinidase Deficiency

Mendelian MONDO:0009665 Pathograph 46 Show in embeddings browser Metabolic Disease Inborn Error of Metabolism

Biotinidase deficiency is an autosomal recessive disorder of biotin recycling caused by biallelic pathogenic variants in BTD. Deficient biotinidase activity limits release of free biotin from biocytin and biotinyl-peptides, producing secondary functional deficiency of biotin-dependent carboxylases. Untreated profound deficiency can cause metabolic acidosis, organic aciduria, seizures, developmental impairment, neurocutaneous disease, hearing loss, and optic atrophy; partial deficiency may become symptomatic during physiologic stress. Newborn screening followed by lifelong oral free biotin prevents symptoms in presymptomatically treated individuals, while delayed treatment may leave irreversible auditory, visual, or developmental deficits.

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1
Mappings
1
Inheritance
5
Pathophys.
28
Phenotypes
3
Gaps
46
Pathograph
1
Genes
3
Variants
6
Medical Actions
2
Subtypes
1
Differentials
1
Models
20
References
1
Deep Research
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Classifications

Harrison's Part
ENDOCRINOLOGY METABOLISM
🔗

Mappings

MONDO
MONDO:0009665 biotinidase deficiency
skos:exactMatch Orphanet ORPHA:79241
Orphanet maps ORPHA:79241 exactly to the MONDO concept used by this entry.
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
Biotinidase deficiency results from biallelic pathogenic BTD variants.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:20301497 SUPPORT Human Clinical
"Biotinidase deficiency is inherited in an autosomal recessive manner."
Current GeneReviews states the mode of inheritance.
ORPHA:79241 SUPPORT Other
"Autosomal recessive"
Orphanet independently records autosomal recessive inheritance.
◆

Subtypes

2
Profound biotinidase deficiency
Less than 10% of mean normal serum biotinidase activity. Untreated symptoms usually begin from the first week of life through childhood and can involve neurologic, cutaneous, auditory, visual, and metabolic systems.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Symptoms of untreated profound biotinidase deficiency (<10% mean normal serum biotinidase activity) usually appear between ages one week and ten years"
Current GeneReviews defines profound deficiency by residual activity and describes its untreated age range.
Partial biotinidase deficiency
Ten to 30% of mean normal serum biotinidase activity. Affected individuals may remain asymptomatic and may manifest disease only during infection or other physiologic stress.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Individuals with partial biotinidase deficiency (10%-30% of mean normal serum biotinidase activity) may develop symptoms only when stressed, such as during infection."
Current GeneReviews defines partial deficiency and bounds its stress-associated clinical expression.
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Discussions and Knowledge Gaps

3
Which cellular events determine whether auditory, optic, and developmental injury remains reversible after biotin is started?
HUMAN MODEL MISMATCH OPEN gap_human_sensory_injury_reversibility
Attached to
pathophysiology#Central nervous system vulnerability and white matter injury treatments#Oral biotin supplementation animal_models#Mus musculus
The knockout mouse shows rapid neurologic, myelin, and axonal recovery after biotin, whereas established hearing loss, optic atrophy, and developmental impairment in humans are commonly incomplete responders. The temporal and cell-type-specific transition to irreversible injury is not resolved by either evidence base.
Show evidence (2 references)
PMID:20301497 SUPPORT Human Clinical
"optic atrophy, hearing loss, and developmental delay, may improve but are usually not completely reversible with the initiation of biotin therapy."
Current GeneReviews documents the human residual-injury boundary.
PMID:22579707 SUPPORT Model Organism
"With biotin treatment, the symptomatic mice improved neurologically and the white matter abnormalities resolved."
The mouse rescue exposes the difference from commonly persistent human sensory injury.
What is the untreated lifetime penetrance and stress-specific risk of biochemically confirmed partial biotinidase deficiency?
KNOWLEDGE GAP OPEN gap_partial_deficiency_natural_history
Attached to
has_subtypes#Partial biotinidase deficiency treatments#Oral biotin supplementation
Lifelong free biotin is the current recommendation and should not be withheld. However, widespread presymptomatic screening and treatment leave limited direct observation of the untreated partial-deficiency natural history, including which infections or physiologic stresses precipitate disease.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Individuals with partial biotinidase deficiency (10%-30% of mean normal serum biotinidase activity) may develop symptoms only when stressed, such as during infection."
Current GeneReviews identifies stress-related expression without quantifying lifetime penetrance.
How should transcript-specific BTD variant nomenclature and regional genotype associations be reconciled with measured enzyme-activity classes?
KNOWLEDGE GAP OPEN gap_genotype_activity_classification
Attached to
genetic#BTD gene variants causing biotinidase deficiency diagnosis#Serum or plasma biotinidase enzyme-activity assay
Severity is defined biochemically, while published cohorts use different variant numbering and show that a frequent homozygous genotype can retain activity above the partial-deficiency range. Harmonized transcript nomenclature and assay-aware interpretation are needed before using regional genotype associations prognostically.
Show evidence (1 reference)
PMID:39451125 SUPPORT Human Clinical
"Biotinidase enzyme activity was above 30% in 97.3% of patients with a homozygous p.D424His mutation"
The cohort demonstrates why genotype alone cannot substitute for the biochemical severity threshold.
⚙

Pathophysiology

5
Impaired biotin recycling
Loss of biotinidase activity prevents efficient recycling of biotin from biocytin and biotinyl-peptides, depleting the free-biotin pool.
hepatocyte CL:0000182 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves hepatocyte (CL:0000182). CL:0000182 is a cell type from the Cell Ontology.
BTD hgnc:1122 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves BTD (hgnc:1122). hgnc:1122 is a gene from the HUGO Gene Nomenclature Committee.
biotin metabolic process GO:0006768 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves biotin metabolic process (GO:0006768). GO:0006768 is a biological process from the Gene Ontology.
biotinidase activity GO:0047708 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased biotinidase activity (GO:0047708). GO:0047708 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Secondary multiple carboxylase deficiency Depletion of recycled free biotin limits formation of active holocarboxylases.
Decreased biotinidase activity BTD pathogenic variation is reflected clinically by reduced serum biotinidase activity.
Show evidence (1 reference)
PMID:38928282 SUPPORT Other
"Biotin status/homeostasis in human individuals depends on several factors, including efficiency/deficiency of the enzymes involved in biotin recycling within the human organism (biotinidase, holocarboxylase synthetase)"
Directly supports the role of biotinidase in biotin recycling and its link to carboxylase function.
Secondary multiple carboxylase deficiency
Inadequate free biotin impairs holocarboxylase formation, producing functional deficiency of the four biotin-dependent carboxylases.
mitochondrion GO:0005739 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves mitochondrion (GO:0005739). GO:0005739 is a cellular component from the Gene Ontology.
Downstream
Disrupted intermediary metabolism and organic aciduria Functional loss of biotin-dependent carboxylases produces toxic metabolite accumulation.
Show evidence (1 reference)
PMID:9350481 SUPPORT Other
"Acquired biotin deficiency and the two known congenital disorders of biotin metabolism, biotinidase and holocarboxylase synthetase (HCS) deficiency, all lead to deficiency of the 4 biotin-dependent carboxylases, i.e. to multiple carboxylase deficiency (MCD)."
Review evidence directly supports secondary deficiency of all four biotin-dependent carboxylases in biotinidase deficiency.
Disrupted intermediary metabolism and organic aciduria
Functional loss of biotin-dependent carboxylases causes characteristic biochemical derangements including lactic acidosis (pyruvate carboxylase impairment), propionate and methylcitrate accumulation (propionyl-CoA carboxylase impairment), and 3-hydroxyisovalerate accumulation (3-methylcrotonyl-CoA carboxylase impairment).
hepatocyte CL:0000182 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves hepatocyte (CL:0000182). CL:0000182 is a cell type from the Cell Ontology.
gluconeogenesis GO:0006094 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves gluconeogenesis (GO:0006094). GO:0006094 is a biological process from the Gene Ontology. propionate catabolic process GO:0019543 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves propionate catabolic process (GO:0019543). GO:0019543 is a biological process from the Gene Ontology. leucine catabolic process GO:0006552 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves leucine catabolic process, annotated with L-leucine catabolic process (GO:0006552). GO:0006552 is a biological process from the Gene Ontology.
pyruvate carboxylase activity GO:0004736 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased pyruvate carboxylase activity (GO:0004736). GO:0004736 is a molecular function from the Gene Ontology. ↓ DECREASED propionyl-CoA carboxylase activity GO:0004658 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased propionyl-CoA carboxylase activity (GO:0004658). GO:0004658 is a molecular function from the Gene Ontology. ↓ DECREASED methylcrotonoyl-CoA carboxylase activity GO:0004485 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased methylcrotonoyl-CoA carboxylase activity (GO:0004485). GO:0004485 is a molecular function from the Gene Ontology. ↓ DECREASED acetyl-CoA carboxylase activity GO:0003989 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased acetyl-CoA carboxylase activity (GO:0003989). GO:0003989 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Central nervous system vulnerability and white matter injury Toxic metabolite buildup and impaired carboxylase activity produce neurologic vulnerability.
Dermatologic manifestations from systemic biotin depletion Systemic biotin depletion and impaired fatty-acid metabolism affect skin and mucocutaneous tissues.
3-Hydroxyisovalerylcarnitine (C5-OH) Secondary 3-methylcrotonyl-CoA carboxylase impairment raises plasma C5-OH.
3-Hydroxyisovaleric acid Secondary leucine-catabolism impairment raises urinary 3-hydroxyisovaleric acid.
Propionylcarnitine (C3) Propionyl-CoA carboxylase impairment can elevate C3-acylcarnitine.
Organic aciduria Multiple carboxylase deficiency produces characteristic urinary organic acid abnormalities.
Metabolic acidosis Accumulation of organic acids and lactate manifests as metabolic acidosis.
Metabolic ketoacidosis Catabolic stress in multiple carboxylase deficiency can produce ketoacidosis.
Hyperammonemia Secondary organic-acid accumulation can disrupt nitrogen disposal and produce hyperammonemia.
Failure to thrive Chronic metabolic derangement and feeding difficulty impair growth.
Lethargy Metabolic decompensation can present with lethargy.
Respiratory distress Systemic metabolic decompensation can include respiratory distress.
Apnea Respiratory involvement during systemic disease can include apnea.
Laryngeal stridor Airway involvement can present as laryngeal stridor.
Show evidence (2 references)
PMID:37373384 SUPPORT Human Clinical
"BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine"
Documents the specific metabolite accumulation pattern in biotinidase deficiency.
PMID:24075304 SUPPORT Model Organism
"a knock-out biotinidase-deficient mouse from a C57BL/6 background that was fed a low biotin diet develops severe ATP deficit with activation of the energy sensor adenosine monophosphate (AMP)-activated protein kinase (AMPK), inhibition of the signaling protein mTOR"
The knockout model provides experimental evidence for cellular energy stress downstream of biotinidase loss, while extrapolation to each human tissue remains incomplete.
Central nervous system vulnerability and white matter injury
Neurologic disease in biotinidase deficiency includes white-matter injury. Human imaging has documented cerebellar hypoplasia and leukodystrophy, while the dietary-challenge knockout mouse develops demyelination, axonal degeneration, ventriculomegaly, and corpus callosum compression.
oligodendrocyte CL:0000128 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves oligodendrocyte (CL:0000128). CL:0000128 is a cell type from the Cell Ontology.
myelination GO:0042552 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves myelination (GO:0042552). GO:0042552 is a biological process from the Gene Ontology.
brain white matter UBERON:0003544 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in brain white matter (UBERON:0003544). UBERON:0003544 is an anatomical location from the Uberon multi-species anatomy ontology. cerebellum UBERON:0002037 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebellum (UBERON:0002037). UBERON:0002037 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Brain imaging abnormality White-matter and cerebellar abnormalities manifest as abnormal brain imaging.
Seizures CNS vulnerability manifests clinically with seizures.
Infantile spasms Infantile spasms are a seizure phenotype within early CNS involvement.
Global developmental delay Early CNS injury and metabolic vulnerability can impair development.
Muscular hypotonia CNS and motor pathway involvement can manifest with hypotonia.
Ataxia Biotinidase deficiency can manifest with ataxia.
Intellectual disability Delayed treatment can leave persistent cognitive deficits after CNS injury.
Spastic paraparesis Biotinidase deficiency can manifest with spastic paraparesis.
Myelopathy Symptomatic biotinidase deficiency can manifest with myelopathy.
Limb muscle weakness CNS and motor pathway involvement can manifest with limb muscle weakness.
Sensorineural hearing impairment Biotinidase deficiency can produce sensorineural hearing impairment.
Optic atrophy Biotinidase deficiency can manifest with optic atrophy.
Optic neuropathy Biotinidase deficiency can manifest with optic neuropathy.
Show evidence (4 references)
PMID:36759144 SUPPORT Human Clinical
"In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups"
The multicenter series documents brain imaging abnormalities across age groups without specifying individual structures in the cached abstract.
PMID:37373384 SUPPORT Human Clinical
"The brain MRI at 12 months showed cerebellar hypoplasia and multiple foci of leukodystrophy"
Case demonstrating cerebellar and white matter injury in profound biotinidase deficiency.
PMID:22579707 SUPPORT Model Organism
"Demyelination, axonal degeneration, ventriculomegaly, and corpus callosum compression were found in the brains of untreated, symptomatic enzyme-deficient mice."
The knockout model experimentally supports white-matter and axonal injury downstream of profound enzyme deficiency.
+ 1 more reference
Dermatologic manifestations from systemic biotin depletion
Skin rash and alopecia result from disrupted biotin-dependent metabolism affecting rapidly dividing cutaneous tissues. Dermatologic features are among the most common presenting signs of biotinidase deficiency.
keratinocyte CL:0000312 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves keratinocyte (CL:0000312). CL:0000312 is a cell type from the Cell Ontology.
fatty acid biosynthetic process GO:0006633 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves fatty acid biosynthetic process (GO:0006633). GO:0006633 is a biological process from the Gene Ontology.
skin of body UBERON:0002097 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in skin of body (UBERON:0002097). UBERON:0002097 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Skin rash Cutaneous biotin-dependent metabolic disruption manifests as rash.
Eczematoid dermatitis Eczematoid dermatitis is a specific cutaneous manifestation of systemic biotin depletion.
Alopecia Impaired skin appendage metabolism can manifest with alopecia.
Recurrent fungal infections Mucocutaneous vulnerability can manifest as recurrent fungal infections.
Conjunctivitis Ocular surface involvement can manifest as conjunctivitis.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Quantifies skin involvement at 53.7% of symptomatic cases in the largest systematic review.
⬡

Pathograph

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

28
Cardiovascular 1
Conjunctivitis OCCASIONAL HP:0000509 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Conjunctivitis (HP:0000509). HP:0000509 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%)"
Eye involvement at 34.4% includes conjunctivitis as a specific presentation.
ORPHA:79241 SUPPORT Other
"HP:0000509 | Conjunctivitis | Occasional (29-5%)"
Orphanet classifies conjunctivitis as occasional in biotinidase deficiency.
Ear 1
Sensorineural hearing impairment FREQUENT HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Auditory involvement at 26.9% supports sensorineural hearing impairment as a significant phenotype.
PMID:39451125 SUPPORT Human Clinical
"Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation"
Documents hearing loss in a Turkish cohort and links it to specific BTD variants.
ORPHA:79241 SUPPORT Other
"HP:0000407 | Sensorineural hearing impairment | Frequent (79-30%)"
Orphanet classifies sensorineural hearing impairment as frequent in biotinidase deficiency.
Eye 1
Optic atrophy OCCASIONAL HP:0000648 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Optic atrophy (HP:0000648). HP:0000648 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%)"
Eye involvement at 34.4% includes optic atrophy; Orphanet classifies optic atrophy specifically as occasional.
PMID:40190376 SUPPORT Human Clinical
"Comprehensive ophthalmic examination revealed bilateral optic neuropathy. Laboratory testing showed a biotinidase level of <0.1"
Case report demonstrates bilateral optic neuropathy with improvement after biotin supplementation.
ORPHA:79241 SUPPORT Other
"HP:0000648 | Optic atrophy | Occasional (29-5%)"
Orphanet classifies optic atrophy as occasional in biotinidase deficiency.
Genitourinary 1
Organic aciduria VERY_FREQUENT HP:0001992 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Organic aciduria (HP:0001992). HP:0001992 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"characteristic abnormal organic acid metabolites were found in 57.1%"
Systematic review found organic aciduria in 57.1% of symptomatic cases when tested; frequency is VERY_FREQUENT per Orphanet, reflecting expected biochemical abnormality in untreated disease.
ORPHA:79241 SUPPORT Other
"HP:0001992 | Organic aciduria | Very frequent (99-80%)"
Orphanet is the authoritative frequency source here; the lower PMID figure reflects incomplete metabolic workups in a heterogeneous cohort.
Immune 2
Skin rash FREQUENT HP:0000988 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Skin rash (HP:0000988). HP:0000988 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%)"
Skin involvement at 53.7% supports dermatitis as a frequent phenotype.
Eczematoid dermatitis OCCASIONAL HP:0000964 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Eczematoid dermatitis (HP:0000964). HP:0000964 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%)"
Skin involvement at 53.7% includes eczematoid dermatitis as a specific presentation.
ORPHA:79241 SUPPORT Other
"HP:0000964 | Eczematoid dermatitis | Occasional (29-5%)"
Orphanet classifies eczematoid dermatitis as occasional in biotinidase deficiency.
Integument 1
Alopecia OCCASIONAL HP:0001596 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Alopecia (HP:0001596). HP:0001596 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Skin involvement at 53.7% includes alopecia; Orphanet classifies alopecia specifically as occasional.
ORPHA:79241 SUPPORT Other
"HP:0001596 | Alopecia | Occasional (29-5%)"
Orphanet classifies alopecia as occasional in biotinidase deficiency.
Limbs 1
Limb muscle weakness OCCASIONAL HP:0003690 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Limb muscle weakness (HP:0003690). HP:0003690 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0003690 | Limb muscle weakness | Occasional (29-5%)"
Orphanet provides the disease-phenotype association and frequency band.
Metabolism 2
Metabolic acidosis FREQUENT HP:0001942 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Metabolic acidosis (HP:0001942). HP:0001942 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"metabolic acidosis was present in 42.4% of symptomatic individuals"
Directly quantifies metabolic acidosis frequency at 42.4% in the 1113-case systematic review.
Hyperammonemia FREQUENT HP:0001987 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperammonemia (HP:0001987). HP:0001987 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0001987 | Hyperammonemia | Frequent (79-30%)"
Orphanet classifies hyperammonemia as frequent in biotinidase deficiency.
Musculoskeletal 2
Muscular hypotonia FREQUENT HP:0001252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypotonia (HP:0001252). HP:0001252 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37373384 SUPPORT Human Clinical
"Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive"
Case report documents hypotonia as a prominent feature in biotinidase deficiency.
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%)"
Nervous system involvement at 67.2% in the systematic review supports hypotonia as a frequent neurological manifestation.
Spastic paraparesis OCCASIONAL HP:0002313 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spastic paraparesis (HP:0002313). HP:0002313 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
Orphanet classifies spastic paraparesis as occasional in biotinidase deficiency.
Nervous System 6
Seizures FREQUENT HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Nervous system involvement at 67.2% supports seizures as a frequent neurological phenotype.
Global developmental delay OCCASIONAL HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37373384 SUPPORT Human Clinical
"Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive"
Case report documents severe psychomotor retardation in a child with profound biotinidase deficiency.
ORPHA:79241 SUPPORT Other
"HP:0001263 | Global developmental delay | Occasional (29-5%)"
Orphanet classifies global developmental delay as occasional in biotinidase deficiency.
Ataxia OCCASIONAL HP:0001251 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ataxia (HP:0001251). HP:0001251 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0001251 | Ataxia | Occasional (29-5%)"
Orphanet classifies ataxia as occasional in biotinidase deficiency.
Intellectual disability OCCASIONAL HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37373384 SUPPORT Human Clinical
"the therapy failed to show any evident effects on poor feeding and intellectual disability"
Case report demonstrates that intellectual disability may be irreversible once established despite biotin treatment.
Myelopathy OCCASIONAL HP:0002196 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myelopathy (HP:0002196). HP:0002196 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0002196 | Myelopathy | Occasional (29-5%)"
Orphanet provides the disease-phenotype association and frequency band.
Lethargy OCCASIONAL HP:0001254 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Lethargy (HP:0001254). HP:0001254 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0001254 | Lethargy | Occasional (29-5%)"
Orphanet classifies lethargy as occasional in biotinidase deficiency.
Respiratory 2
Respiratory distress OCCASIONAL HP:0002098 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Respiratory distress (HP:0002098). HP:0002098 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
ORPHA:79241 SUPPORT Other
"HP:0002098 | Respiratory distress | Occasional (29-5%)"
Orphanet classifies respiratory distress as occasional in biotinidase deficiency.
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Respiratory system involvement at 17.8% supports respiratory involvement broadly; Orphanet provides the specific respiratory distress term.
Apnea OCCASIONAL HP:0002104 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Apnea (HP:0002104). HP:0002104 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)"
Respiratory system involvement at 17.8% includes apneic episodes.
ORPHA:79241 SUPPORT Other
"HP:0002104 | Apnea | Occasional (29-5%)"
Orphanet classifies apnea as occasional in biotinidase deficiency.
Growth 1
Failure to thrive OCCASIONAL HP:0001508 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Failure to thrive (HP:0001508). HP:0001508 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37373384 SUPPORT Human Clinical
"Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive"
Case report documents failure to thrive as a clinical feature of profound biotinidase deficiency.
Other 7
Optic neuropathy OCCASIONAL HP:0001138 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Optic neuropathy (HP:0001138). HP:0001138 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0001138 | Optic neuropathy | Occasional (29-5%)"
Orphanet provides the disease-phenotype association and frequency band.
Metabolic ketoacidosis VERY_FREQUENT HP:0005979 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Metabolic ketoacidosis (HP:0005979). HP:0005979 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"metabolic acidosis was present in 42.4% of symptomatic individuals"
The systematic review supports metabolic acidosis broadly; Orphanet provides the specific metabolic ketoacidosis support.
ORPHA:79241 SUPPORT Other
"HP:0005979 | Metabolic ketoacidosis | Very frequent (99-80%)"
Orphanet classifies metabolic ketoacidosis as very frequent in biotinidase deficiency.
Laryngeal stridor OCCASIONAL HP:0006511 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Laryngeal stridor (HP:0006511). HP:0006511 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0006511 | Laryngeal stridor | Occasional (29-5%)"
Orphanet classifies laryngeal stridor as occasional in biotinidase deficiency.
Recurrent fungal infections OCCASIONAL HP:0002841 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent fungal infections (HP:0002841). HP:0002841 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0002841 | Recurrent fungal infections | Occasional (29-5%)"
Orphanet classifies recurrent fungal infections as occasional in biotinidase deficiency.
Brain imaging abnormality FREQUENT HP:0410263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Brain imaging abnormality (HP:0410263). HP:0410263 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:36759144 SUPPORT Human Clinical
"In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups"
Multicenter neuroimaging study documenting characteristic brain MRI patterns.
ORPHA:79241 SUPPORT Other
"HP:0410263 | Brain imaging abnormality | Frequent (79-30%)"
Orphanet classifies brain imaging abnormality as frequent in biotinidase deficiency.
Infantile spasms OCCASIONAL HP:0012469 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"HP:0012469 | Infantile spasms | Occasional (29-5%)"
Orphanet classifies infantile spasms as occasional in biotinidase deficiency.
Decreased biotinidase activity VERY_FREQUENT Decreased circulating biotinidase concentration HP:0410145 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased biotinidase activity, annotated with Decreased circulating biotinidase concentration (HP:0410145). HP:0410145 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:38141137 SUPPORT Human Clinical
"Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%"
Large cohort quantifies the distribution of enzyme deficiency severity categories.
ORPHA:79241 SUPPORT Other
"HP:0410145 | Decreased biotinidase activity | Very frequent (99-80%)"
Orphanet classifies decreased biotinidase activity as very frequent (diagnostic hallmark).
🧬

Genetic Associations

1
BTD gene variants causing biotinidase deficiency
Gene: BTD hgnc:1122 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is BTD (hgnc:1122). hgnc:1122 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (4 references)
PMID:38141137 SUPPORT Human Clinical
"Two hundred forty-seven cases were included in the study who were admitted to the Department of Pediatric Metabolism"
Large cohort study providing comprehensive genotype-phenotype correlations in biotinidase deficiency.
PMID:39451125 SUPPORT Human Clinical
"This study provides a detailed analysis of genetic diversity and clinical presentation in biotinidase deficiency cases in Eastern Anatolia, demonstrating the efficacy of biotin treatment"
Regional cohort study demonstrating genetic diversity and variant-phenotype relationships.
ORPHA:79241 SUPPORT Other
"BTD | biotinidase | hgnc:1122 | Disease-causing germline mutation(s) in"
Orphanet confirms BTD as the disease-causing gene for biotinidase deficiency.
+ 1 more reference
Variants (3)
c.1270G>C (p.Asp424His)
This was the most frequent BTD variant in two Turkish cohorts. In one cohort, 97.3% of homozygotes had enzyme activity above 30%, so this genotype should not be equated automatically with biochemical partial deficiency without an activity assay. The cited studies use p.Asp424His; cross-cohort comparison requires normalization to a specified reference transcript and protein sequence. Regional frequency should not be generalized worldwide.
Show evidence (2 references)
PMID:39451125 SUPPORT Human Clinical
"the most frequent variant was c.1270G > C | p.Asp424His. Biotinidase enzyme activity was above 30% in 97.3% of patients with a homozygous p.D424His mutation"
The regional cohort identifies D424H as frequent and, importantly, documents activity above the partial-deficiency range in most homozygotes.
PMID:38141137 SUPPORT Human Clinical
"The most common pathogenic variants were c.1270G > C (p.Asp424His), c.410G > A (p.Arg137His), and c.38_44delGCGCTGinsTCC (p.Cys13Phefs*36) in BTD gene"
Confirms D424H as the most common variant in a large Turkish cohort.
c.410G>A (p.Arg137His)
This variant was among those associated with the largest enzyme-activity decreases and was enriched among neurologically symptomatic individuals in regional cohorts. Those associations are not deterministic for an individual patient.
Show evidence (2 references)
PMID:39451125 SUPPORT Human Clinical
"The mutations that caused the most significant decrease in enzyme activity were c.410G > A p.Arg137His, c.38_delinsTCC p.Cys13phefs*36, and c.1535C > T p.Thr512Met"
Identifies R137H as causing significant enzyme activity reduction.
PMID:38141137 SUPPORT Human Clinical
"The c.410G > A and c.38_44delGCGCTGinsTCC variants were more common in the patients with neurological symptoms"
Links R137H variant to neurological presentation.
c.38_44delGCGCTGinsTCC (p.Cys13Phefs*36)
This frameshift was associated with marked enzyme-activity reduction, neurologic manifestations, hearing loss, and optic atrophy in regional cohorts. The small numbers and inclusion of both homozygous and heterozygous observations limit individual prognostic prediction.
Show evidence (2 references)
PMID:39451125 SUPPORT Human Clinical
"Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation (homozygous or heterozygous)"
Links this frameshift variant to severe sensory complications.
PMID:38141137 SUPPORT Human Clinical
"The c.410G > A and c.38_44delGCGCTGinsTCC variants were more common in the patients with neurological symptoms"
Confirms association of this variant with neurological symptoms in a large cohort.
🗃️

External Assertions

2
Orphanet biotinidase deficiency record
Orphanet structured disease record ORPHA:79241
The structured Orphanet record supplies disease scope, inheritance, epidemiology, gene association, phenotype frequencies, and the exact MONDO mapping.
Show evidence (1 reference)
ORPHA:79241 SUPPORT Other
"MONDO:0009665 | Exact"
Orphanet maps the disease record exactly to MONDO:0009665.
ClinGen BTD gene-disease validity assertion
ClinGen gene disease validity CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z
ClinGen's Hearing Loss Gene Curation Expert Panel classified the autosomal-recessive BTD–biotinidase deficiency relationship as definitive.
Show evidence (1 reference)
CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z SUPPORT Other
"BTD | HGNC:1122 | biotinidase deficiency | MONDO:0009665 | AR | Definitive"
The structured ClinGen assertion directly supports definitive gene-disease validity.
💊

Medical Actions

6
Oral biotin supplementation
Category: Therapeutic Action: nutritional supplementationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is nutritional supplementation, annotated with Nutritional Support (NCIT:C15433). NCIT:C15433 is a clinical intervention from the NCI Thesaurus. Ontology label: Nutritional Support NCIT:C15433
Agent: biotin CHEBI:15956 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses biotin (CHEBI:15956). CHEBI:15956 is a therapeutic agent from Chemical Entities of Biological Interest.
Lifelong oral free biotin is the disease-specific therapy for both profound and partial deficiency. Current GeneReviews dosing is 5-10 mg/day for profound deficiency and 2.5-10 mg/day for partial deficiency. Presymptomatic adherence prevents manifestations; established hearing loss, optic atrophy, or developmental impairment may not completely reverse.
Mechanism Target:
BYPASSES Impaired biotin recycling — Pharmacologic free biotin supplementation bypasses defective biotin recycling and restores biotin availability for carboxylase biotinylation.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"Biotin treatment led to clinical stability or improvement in 89.2% of individuals."
Treatment-response evidence supports free biotin supplementation as the disease-modifying intervention.
RESTORES Disrupted intermediary metabolism and organic aciduria — Providing free biotin restores downstream biotin-dependent carboxylase function and reduces metabolic instability.
Show evidence (1 reference)
PMID:38928282 SUPPORT Other
"administration of biotin at high/"pharmacological" doses has been proposed to treat specific defects/deficiencies and human disorders"
Review evidence supports pharmacologic biotin as treatment for biotin-homeostasis defects.
Target Phenotypes: Seizure HP:0001250 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology. Metabolic acidosis HP:0001942 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Metabolic acidosis (HP:0001942). HP:0001942 is a phenotype from the Human Phenotype Ontology. Organic aciduria HP:0001992 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Organic aciduria (HP:0001992). HP:0001992 is a phenotype from the Human Phenotype Ontology. Skin rash HP:0000988 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Skin rash (HP:0000988). HP:0000988 is a phenotype from the Human Phenotype Ontology. Alopecia HP:0001596 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Alopecia (HP:0001596). HP:0001596 is a phenotype from the Human Phenotype Ontology.
Show evidence (4 references)
PMID:20301497 SUPPORT Human Clinical
"All individuals with profound biotinidase deficiency (<10% mean normal serum enzyme activity) and those with partial biotinidase deficiency (10%-30% of mean normal serum enzyme activity) should be treated with oral biotin in the free form as opposed to the protein-bound form; biotin therapy is lifelong."
Current GeneReviews recommends lifelong oral free biotin for both biochemical severity classes.
PMID:20301497 SUPPORT Human Clinical
"Oral biotin of 5-10 mg/day for those who have <10% mean normal serum enzyme activity and 2.5-10 mg/day in those who have 10%-30% of mean normal serum enzyme activity."
Current GeneReviews supplies severity-specific dose ranges.
PMID:37027963 SUPPORT Human Clinical
"Biotin treatment led to clinical stability or improvement in 89.2% of individuals. 1.6% of reported individuals with BD died due to non-availability of treatment or late diagnosis"
Systematic review of 1113 cases demonstrating high efficacy of biotin treatment.
+ 1 more reference
Antiseizure medication
Category: Therapeutic Action: antiepileptic drug therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is antiepileptic drug therapy, annotated with Anticonvulsant Therapy (NCIT:C64172). NCIT:C64172 is a clinical intervention from the NCI Thesaurus. Ontology label: Anticonvulsant Therapy NCIT:C64172
Anticonvulsant therapy may be needed for seizure management, although seizures often resolve with biotin supplementation alone. Antiepileptic therapy alone without biotin is typically insufficient.
Target Phenotypes: Seizure HP:0001250 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:37373384 SUPPORT Human Clinical
"The result of antiepileptic therapy was not satisfying"
Case demonstrates that antiepileptic therapy alone is insufficient and biotin is the essential treatment.
Genetic counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Genetic counseling is recommended for affected families to discuss autosomal recessive inheritance, 25% recurrence risk, carrier testing, and prenatal/preimplantation genetic testing options.
Show evidence (3 references)
PMID:20301497 SUPPORT Human Clinical
"each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier."
Current GeneReviews provides the autosomal-recessive recurrence risks used in counseling.
PMID:37027963 SUPPORT Human Clinical
"Biotinidase deficiency (BD) is an autosomal recessively inherited disorder"
Autosomal recessive inheritance pattern supports the role of genetic counseling.
PMID:38141137 SUPPORT Human Clinical
"Biotinidase deficiency (BD) is an autosomal recessive inherited metabolic disorder"
Genetic basis of the disorder supports counseling for recurrence risk assessment.
Supportive care
Category: Therapeutic Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
Symptomatic metabolic decompensation may require hydration and bicarbonate while biotin corrects the underlying derangement. Developmental, educational, ophthalmologic, and audiologic support address residual complications.
Target Phenotypes: Metabolic acidosis HP:0001942 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Metabolic acidosis (HP:0001942). HP:0001942 is a phenotype from the Human Phenotype Ontology. Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology. Optic atrophy HP:0000648 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Optic atrophy (HP:0000648). HP:0000648 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Hydration and bicarbonate in those with metabolic decompensation and acidosis, although biotin therapy can rapidly resolve the metabolic derangements within hours to days"
Current GeneReviews supports acute hydration and bicarbonate while disease-specific therapy takes effect.
Audiological management
Category: Therapeutic Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Regular audiological assessment and hearing aid or cochlear implant consideration for patients with sensorineural hearing loss, which may be irreversible once established.
Target Phenotypes: Sensorineural hearing impairment HP:0000407 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:20301497 SUPPORT Human Clinical
"hearing aids and, if severe, consideration of cochlear implants for those with hearing loss."
Current GeneReviews directly supports hearing aids and cochlear-implant consideration.
PMID:37027963 SUPPORT Human Clinical
"BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%)"
Auditory involvement at 26.9% supports the need for audiological monitoring and management.
PMID:39451125 SUPPORT Human Clinical
"Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation"
Documents hearing loss as a significant complication requiring audiological management.
Avoidance of raw egg white
Action: dietary interventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is dietary intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. Ontology label: Dietary Intervention NCIT:C15447
Raw egg white contains avidin, which binds biotin and reduces its bioavailability. Thorough cooking inactivates avidin.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Raw eggs should be avoided because they contain avidin, an egg white protein that binds biotin, thus decreasing its bioavailability."
Current GeneReviews explicitly identifies raw eggs as a circumstance to avoid.
🔬

Biochemical Markers

5
3-Hydroxyisovalerylcarnitine (C5-OH) (INCREASED)
Context: Elevated C5-OH acylcarnitine is a characteristic plasma marker of impaired leucine catabolism via 3-methylcrotonyl-CoA carboxylase deficiency. Detectable on newborn screening acylcarnitine profiles.
Pathograph Readouts
Readout Of Disrupted intermediary metabolism and organic aciduria Positive Diagnostic
Elevated C5-OH reports secondary multiple-carboxylase dysfunction and the leucine-catabolism branch of the metabolic block.
Show evidence (1 reference)
PMID:33572391 SUPPORT Human Clinical
"increased levels of C5OH may be linked to 3-methylcrotonyl-CoA carboxylase activity"
This human newborn-screening report explicitly links C5OH elevation to the 3-methylcrotonyl-CoA carboxylase branch affected by BTD deficiency.
Show evidence (1 reference)
PMID:37373384 SUPPORT Human Clinical
"BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma"
Directly identifies elevated C5-OH as a primary plasma marker.
3-Hydroxyisovaleric acid (INCREASED)
Context: Elevated urinary 3-hydroxyisovaleric acid is a characteristic organic acid marker reflecting impaired leucine catabolism via 3-methylcrotonyl-CoA carboxylase.
Pathograph Readouts
Readout Of Disrupted intermediary metabolism and organic aciduria Positive Diagnostic
Elevated urinary 3-hydroxyisovaleric acid reports impaired 3-methylcrotonyl-CoA carboxylase-dependent leucine catabolism.
Show evidence (1 reference)
PMID:37373384 SUPPORT Human Clinical
"primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine"
This case report directly identifies urinary 3-hydroxyisovaleric acid accumulation downstream of impaired BTD-dependent carboxylase function.
Show evidence (2 references)
PMID:37373384 SUPPORT Human Clinical
"primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine"
Directly identifies elevated urinary 3-hydroxyisovaleric acid as a characteristic marker.
PMID:37027963 SUPPORT Human Clinical
"characteristic abnormal organic acid metabolites were found in 57.1%"
Confirms organic acid abnormalities in the majority of symptomatic cases.
Propionylcarnitine (C3) (INCREASED)
Context: Elevated C3-acylcarnitine reflects propionyl-CoA carboxylase dysfunction in the setting of secondary multiple carboxylase deficiency.
Pathograph Readouts
Readout Of Disrupted intermediary metabolism and organic aciduria Positive Diagnostic
Elevated C3 reports the propionyl-CoA carboxylase branch of secondary multiple-carboxylase dysfunction.
Show evidence (1 reference)
PMID:33572391 SUPPORT Human Clinical
"mildly elevated C3 levels may reflect propionyl-CoA carboxylase deficiency"
This human newborn-screening report directly links C3 elevation to propionyl-CoA carboxylase deficiency in the BTD deficiency metabolic context.
Show evidence (2 references)
PMID:33572391 SUPPORT Human Clinical
"mildly elevated C3 levels may reflect propionyl-CoA carboxylase deficiency"
Directly supports C3 elevation as a marker of the propionyl-CoA carboxylase branch in biotinidase deficiency.
PMID:38928282 SUPPORT Other
"Biotin status/homeostasis in human individuals depends on several factors, including efficiency/deficiency of the enzymes involved in biotin recycling within the human organism (biotinidase, holocarboxylase synthetase)"
Review supports impaired biotin recycling and downstream carboxylase dysfunction, but does not directly name C3 propionylcarnitine.
Lactate (INCREASED)
Context: Lactic acidosis results from pyruvate carboxylase impairment. Brain lactate may be detectable by magnetic resonance spectroscopy.
Pathograph Readouts
Readout Of Disrupted intermediary metabolism and organic aciduria Positive Diagnostic
Lactate elevation reports impaired pyruvate carboxylase-dependent intermediary metabolism and lactic-acidosis risk.
Show evidence (1 reference)
PMID:9427142 SUPPORT Human Clinical
"Lactate, pyruvate and 3-hydroxyisovaleric acid as metabolic disease markers were measured in blood, cerebrospinal fluid and brain tissue by biochemical analyses or localized magnetic resonance proton spectroscopy."
Human metabolic imaging and biochemical measurements identify lactate as a disease marker in biotinidase deficiency.
Show evidence (3 references)
PMID:9427142 SUPPORT Human Clinical
"Lactate, pyruvate and 3-hydroxyisovaleric acid as metabolic disease markers were measured in blood, cerebrospinal fluid and brain tissue by biochemical analyses or localized magnetic resonance proton spectroscopy."
Directly supports lactate as a biochemical disease marker in biotinidase deficiency.
PMID:3736876 SUPPORT Human Clinical
"this disorder who had high CSF content of lactate that could have contributed to the clinical disorder"
Classic patient report supports increased CSF lactate in biotinidase deficiency.
PMID:37027963 SUPPORT Human Clinical
"metabolic acidosis was present in 42.4% of symptomatic individuals"
Metabolic acidosis in biotinidase deficiency includes lactic acidosis from pyruvate carboxylase dysfunction.
Biotinidase enzyme activity (DECREASED)
Context: Reduced serum biotinidase enzyme activity is the definitive diagnostic marker. Profound deficiency is defined as less than 10% of mean normal activity and partial deficiency as 10-30%.
Pathograph Readouts
Readout Of Impaired biotin recycling Negative Diagnostic
Reduced biotinidase activity directly reports the proximal BTD enzyme defect that impairs biotin recycling.
Show evidence (1 reference)
PMID:38141137 SUPPORT Human Clinical
"Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%"
Cohort enzyme-activity data support reduced biotinidase activity as the diagnostic readout of the proximal mechanism.
Show evidence (2 references)
PMID:40190376 SUPPORT Human Clinical
"Laboratory testing showed a biotinidase level of <0.1 (normal, 5.5-10 nmol/min/ml)"
Case report documents severely reduced biotinidase activity confirming the diagnosis.
PMID:38141137 SUPPORT Human Clinical
"Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%"
Large cohort quantifies the distribution of enzyme deficiency severity categories.
🔬

Diagnosis

3
Serum or plasma biotinidase enzyme-activity assay
Quantitative measurement of biotinidase activity in serum or plasma is the primary confirmatory biochemical test. Residual activity classifies profound deficiency below 10% and partial deficiency at 10%-30% of mean normal activity.
diagnostic procedure NCIT:C18020 NCI Thesaurus (NCIT)
Markers: Biotinidase enzyme activity
Results: Deficient serum or plasma activity confirms the proximal enzyme defect and supplies the biochemical severity classification.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"detection of deficient biotinidase enzyme activity in serum/plasma"
Current GeneReviews identifies deficient serum/plasma enzyme activity as a diagnostic route.
BTD molecular genetic testing
Identification of biallelic pathogenic BTD variants establishes the molecular diagnosis and is particularly useful when enzyme results are ambiguous. Enzyme activity remains important for severity classification.
genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Results: Biallelic pathogenic BTD variants support the molecular diagnosis.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"identification of biallelic pathogenic variants in BTD on molecular genetic testing when the results of enzymatic testing are ambiguous."
Current GeneReviews defines molecular testing as a diagnostic route when enzyme testing is ambiguous.
Newborn screening for biotinidase deficiency
Newborn screening identifies affected infants before symptoms and should be followed by confirmatory serum/plasma enzyme activity testing, with molecular testing when biochemical results are ambiguous.
disease screening NCIT:C15419 NCI Thesaurus (NCIT)
Results: A low screening biotinidase activity result triggers confirmatory biochemical and, when needed, molecular testing.
Show evidence (2 references)
PMID:37027963 SUPPORT Human Clinical
"Newborn screening has had a major positive impact on the outcome of many individuals with BD"
The 1,113-person systematic review supports the clinical utility of newborn screening.
PMID:38141137 SUPPORT Human Clinical
"An analysis of the admission routes of all cases to our clinic revealed 89.5% NBS, 5.7% family screening, and 4.9% suspicious clinical findings suggestive of BD"
A 247-person cohort shows that screening was the predominant diagnostic route.
📈

Progression

2
Presymptomatic detection and prevention
Age: Newborn period onward
Individuals identified before symptoms and maintained on biotin are expected to develop normally without the untreated disease manifestations.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Individuals with biotinidase deficiency who are diagnosed before they have developed symptoms (e.g., by newborn screening) and who are treated with biotin have normal development."
Current GeneReviews directly links presymptomatic diagnosis and biotin treatment to normal development.
Untreated symptomatic disease and residual injury
Age: Infancy through adulthood
Untreated profound deficiency can present from infancy through childhood; adolescents and adults may present with myelopathy and optic neuropathy. Metabolic, feeding, skin, and respiratory findings often respond promptly, whereas established hearing loss, optic atrophy, and developmental impairment may not fully reverse.
Show evidence (1 reference)
PMID:20301497 SUPPORT Human Clinical
"Some symptoms, such as feeding issues, cutaneous manifestations, and respiratory issues, usually resolve with biotin therapy, whereas other manifestations presenting prior to biotin treatment, such as optic atrophy, hearing loss, and developmental delay, may improve but are usually not..."
Current GeneReviews distinguishes reversible manifestations from commonly persistent sensory and developmental injury.
📊

Prevalence

1
Newborn screening cohorts
Birth Prevalence 1.637546 per 100,000 1–9 per 100,000
Newborn-screening studies place overall biotinidase deficiency incidence at roughly 1 in 60,000 births. A Paraná screening cohort found 1 affected infant in 62,500 births overall, with profound and partial deficiency each occurring in 1 in 125,000 births.
Show evidence (4 references)
PMID:2314964 SUPPORT Human Clinical
"The combined incidence of profound and partial deficiency was 1 case per 61,067 live births"
This multicountry newborn-screening survey (~4.4 million newborns screened across 12 countries) provides a commonly cited combined incidence estimate for biotinidase deficiency.
PMID:9713119 SUPPORT Human Clinical
"Screening of 125,000 infants born in Paraná State was carried out to establish the prevalence of biotinidase deficiency. A simple colorimetric procedure was used to detect two infants with biotinidase deficiency (1:62,500), one of them with profound deficiency (1:125,000) and the other with..."
This newborn-screening study independently supports an incidence near 1 in 60,000 births and provides subtype-specific rates for profound and partial deficiency.
ORPHA:79241 SUPPORT Other
"1-9 / 100 000 | Worldwide | Prevalence at birth | PMID:1779651"
Orphanet epidemiology data cites worldwide birth prevalence of 1-9 per 100,000 based on Wolf 1991 screening survey.
+ 1 more reference
🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Biotinidase Deficiency:

Holocarboxylase synthetase deficiency MONDO:0009666
Overlapping Features HLCS deficiency is the other inherited cause of multiple carboxylase deficiency. Direct biotinidase activity and BTD/HLCS molecular testing distinguish these disorders when metabolites indicate multiple carboxylase dysfunction.
Show evidence (1 reference)
PMID:9350481 SUPPORT Other
"the two known congenital disorders of biotin metabolism, biotinidase and holocarboxylase synthetase (HCS) deficiency, all lead to deficiency of the 4 biotin-dependent carboxylases"
The review identifies biotinidase and holocarboxylase synthetase deficiency as distinct inherited routes to the same biochemical pattern.
🐁

Animal Models

1
Homozygous Btd null allele (Btd-/-) Mus musculus Knockout, dietary challenge, and biotin rescue
Btd-null mice lack detectable serum biotinidase activity. A biotin-deficient diet produces neurologic and cutaneous disease, secondary carboxylase deficiency, organic-acid abnormalities, and white-matter/axonal injury; pharmacologic biotin reverses many measured manifestations. The required dietary challenge is an important boundary on direct comparison with untreated human disease.
Absent serum biotinidase activity Neurological deficits Cutaneous abnormalities and alopecia Secondary carboxylase deficiency Demyelination and axonal degeneration Increased urinary 3-hydroxyisovaleric acid
Species
Mus musculus
Genotype
Homozygous Btd null allele (Btd-/-)
Background
Congenic C57BL/6 background after ten backcross generations; animals remain asymptomatic on a biotin-replete standard diet and develop disease manifestations after a low- or biotin-deficient dietary challenge.
Show evidence (4 references)
PMID:21051254 SUPPORT Model Organism
"The mouse has a null mutation that results in no detectable serum biotinidase activity or cross-reacting material to antibody prepared against biotinidase."
The model publication directly defines the null genotype and enzyme phenotype.
PMID:21051254 SUPPORT Model Organism
"When fed a biotin-deficient diet these mice develop neurological and cutaneous symptoms, carboxylase deficiency, mild hyperammonemia, and exhibit increased urinary excretion of 3-hydroxyisovaleric acid and biotin and biotin metabolites."
The dietary-challenge experiment directly documents the neurocutaneous and biochemical disease phenotype.
PMID:22579707 SUPPORT Model Organism
"the chimera with the gene knock-out was generated followed by initial backcross with C57BL/6 background mouse for 10 generations to obtain the biotinidase gene knock-out mouse with C57BL/6 genetic background."
The model publication directly documents the congenic C57BL/6 background.
+ 1 more reference
{ }

Source YAML

click to show 
name: Biotinidase Deficiency
category: Mendelian
creation_date: '2025-06-12T20:16:27Z'
synonyms:
- BTD deficiency
- Biotinidase deficiency, profound
- Biotinidase deficiency, partial
- Late-onset multiple carboxylase deficiency
- Juvenile-onset multiple carboxylase deficiency
description: >-
  Biotinidase deficiency is an autosomal recessive disorder of biotin recycling
  caused by biallelic pathogenic variants in BTD. Deficient biotinidase activity
  limits release of free biotin from biocytin and biotinyl-peptides, producing
  secondary functional deficiency of biotin-dependent carboxylases. Untreated
  profound deficiency can cause metabolic acidosis, organic aciduria, seizures,
  developmental impairment, neurocutaneous disease, hearing loss, and optic
  atrophy; partial deficiency may become symptomatic during physiologic stress.
  Newborn screening followed by lifelong oral free biotin prevents symptoms in
  presymptomatically treated individuals, while delayed treatment may leave
  irreversible auditory, visual, or developmental deficits.
disease_term:
  preferred_term: biotinidase deficiency
  term:
    id: MONDO:0009665
    label: biotinidase deficiency
parents:
- Metabolic Disease
- Inborn Error of Metabolism
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        A late-onset form of multiple carboxylase deficiency, an inborn error of
        biotin metabolism
      explanation: >-
        Orphanet defines the disorder as an inborn error of biotin metabolism,
        supporting its metabolic classification.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0009665
      label: biotinidase deficiency
    mapping_predicate: skos:exactMatch
    mapping_source: Orphanet ORPHA:79241
    mapping_justification: >-
      Orphanet maps ORPHA:79241 exactly to the MONDO concept used by this entry.
external_assertions:
- name: Orphanet biotinidase deficiency record
  source: Orphanet
  assertion_type: structured_disease_record
  external_id: ORPHA:79241
  url: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=79241
  description: >-
    The structured Orphanet record supplies disease scope, inheritance,
    epidemiology, gene association, phenotype frequencies, and the exact MONDO
    mapping.
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MONDO:0009665 | Exact"
    explanation: Orphanet maps the disease record exactly to MONDO:0009665.
- name: ClinGen BTD gene-disease validity assertion
  source: ClinGen
  assertion_type: gene_disease_validity
  external_id: CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z
  url: https://search.clinicalgenome.org/kb/gene-validity
  description: >-
    ClinGen's Hearing Loss Gene Curation Expert Panel classified the
    autosomal-recessive BTD–biotinidase deficiency relationship as definitive.
  evidence:
  - reference: CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z
    reference_title: "BTD / biotinidase deficiency (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "BTD | HGNC:1122 | biotinidase deficiency | MONDO:0009665 | AR | Definitive"
    explanation: The structured ClinGen assertion directly supports definitive gene-disease validity.
has_subtypes:
- name: Profound biotinidase deficiency
  display_name: Profound biotinidase deficiency
  classification: residual_enzyme_activity
  description: >-
    Less than 10% of mean normal serum biotinidase activity. Untreated symptoms
    usually begin from the first week of life through childhood and can involve
    neurologic, cutaneous, auditory, visual, and metabolic systems.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Symptoms of untreated profound biotinidase deficiency (<10% mean normal
      serum biotinidase activity) usually appear between ages one week and ten
      years
    explanation: >-
      Current GeneReviews defines profound deficiency by residual activity and
      describes its untreated age range.
- name: Partial biotinidase deficiency
  display_name: Partial biotinidase deficiency
  classification: residual_enzyme_activity
  description: >-
    Ten to 30% of mean normal serum biotinidase activity. Affected individuals
    may remain asymptomatic and may manifest disease only during infection or
    other physiologic stress.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with partial biotinidase deficiency (10%-30% of mean normal
      serum biotinidase activity) may develop symptoms only when stressed, such
      as during infection.
    explanation: >-
      Current GeneReviews defines partial deficiency and bounds its
      stress-associated clinical expression.
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: Biotinidase deficiency results from biallelic pathogenic BTD variants.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Biotinidase deficiency is inherited in an autosomal recessive manner.
    explanation: Current GeneReviews states the mode of inheritance.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal recessive"
    explanation: Orphanet independently records autosomal recessive inheritance.
prevalence:
- population: Newborn screening cohorts
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 1.637546
  notes: >-
    Newborn-screening studies place overall biotinidase deficiency incidence at
    roughly 1 in 60,000 births. A Paraná screening cohort found 1 affected
    infant in 62,500 births overall, with profound and partial deficiency each
    occurring in 1 in 125,000 births.
  evidence:
  - reference: PMID:2314964
    reference_title: "Screening for biotinidase deficiency in newborns: worldwide experience."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The combined incidence of profound and partial deficiency was 1 case per 61,067 live births"
    explanation: >-
      This multicountry newborn-screening survey (~4.4 million newborns
      screened across 12 countries) provides a commonly cited combined
      incidence estimate for biotinidase deficiency.
  - reference: PMID:9713119
    reference_title: "[Prevalence study of biotinidase deficiency in newborns]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Screening of 125,000 infants born in Paraná State was carried out to establish the prevalence of biotinidase deficiency. A simple colorimetric procedure was used to detect two infants with biotinidase deficiency (1:62,500), one of them with profound deficiency (1:125,000) and the other with partial deficiency (1:125,000) of the enzyme."
    explanation: >-
      This newborn-screening study independently supports an incidence near 1 in
      60,000 births and provides subtype-specific rates for profound and partial
      deficiency.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "1-9 / 100 000 | Worldwide | Prevalence at birth | PMID:1779651"
    explanation: Orphanet epidemiology data cites worldwide birth prevalence of 1-9 per 100,000 based on Wolf 1991 screening survey.
  - reference: PMID:1779651
    reference_title: "Worldwide survey of neonatal screening for biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The incidence of combined profound and partial deficiency is 1:60,089 newborns (1:49,500 to 1:73,100)"
    explanation: Landmark worldwide screening survey of 8.5 million newborns establishing the 1:60,000 global incidence estimate.
progression:
- phase: Presymptomatic detection and prevention
  age_range: Newborn period onward
  notes: >-
    Individuals identified before symptoms and maintained on biotin are
    expected to develop normally without the untreated disease manifestations.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with biotinidase deficiency who are diagnosed before they
      have developed symptoms (e.g., by newborn screening) and who are treated
      with biotin have normal development.
    explanation: >-
      Current GeneReviews directly links presymptomatic diagnosis and biotin
      treatment to normal development.
- phase: Untreated symptomatic disease and residual injury
  age_range: Infancy through adulthood
  notes: >-
    Untreated profound deficiency can present from infancy through childhood;
    adolescents and adults may present with myelopathy and optic neuropathy.
    Metabolic, feeding, skin, and respiratory findings often respond promptly,
    whereas established hearing loss, optic atrophy, and developmental
    impairment may not fully reverse.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Some symptoms, such as feeding issues, cutaneous manifestations, and
      respiratory issues, usually resolve with biotin therapy, whereas other
      manifestations presenting prior to biotin treatment, such as optic
      atrophy, hearing loss, and developmental delay, may improve but are
      usually not completely reversible with the initiation of biotin therapy.
    explanation: >-
      Current GeneReviews distinguishes reversible manifestations from commonly
      persistent sensory and developmental injury.
pathophysiology:
- name: Impaired biotin recycling
  description: 'Loss of biotinidase activity prevents efficient recycling of biotin from biocytin and biotinyl-peptides, depleting the free-biotin pool.

    '
  mechanism_confidence: ESTABLISHED
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: biotin metabolic process
    term:
      id: GO:0006768
      label: biotin metabolic process
  genes:
  - preferred_term: BTD
    term:
      id: hgnc:1122
      label: BTD
  molecular_functions:
  - preferred_term: biotinidase activity
    term:
      id: GO:0047708
      label: biotinidase activity
    modifier: DECREASED
  chemical_entities:
  - preferred_term: biotin
    term:
      id: CHEBI:15956
      label: biotin
    modifier: DECREASED
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  evidence:
  - reference: PMID:38928282
    reference_title: "Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Biotin status/homeostasis in human individuals depends on several factors, including efficiency/deficiency of the enzymes involved in biotin recycling within the human organism (biotinidase, holocarboxylase synthetase)
    explanation: Directly supports the role of biotinidase in biotin recycling and its link to carboxylase function.
  downstream:
  - target: Secondary multiple carboxylase deficiency
    description: Depletion of recycled free biotin limits formation of active holocarboxylases.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body
      explanation: This directly supports carboxylase dysfunction downstream of BTD deficiency.
  - target: Decreased biotinidase activity
    description: BTD pathogenic variation is reflected clinically by reduced serum biotinidase activity.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38141137
      reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%
      explanation: Cohort data support decreased biotinidase activity as the enzyme-level manifestation of BTD deficiency.
- name: Secondary multiple carboxylase deficiency
  description: >-
    Inadequate free biotin impairs holocarboxylase formation, producing
    functional deficiency of the four biotin-dependent carboxylases.
  mechanism_confidence: ESTABLISHED
  biological_scale: MOLECULAR
  cellular_components:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:9350481
    reference_title: "Multiple carboxylase deficiency: inherited and acquired disorders of biotin metabolism."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Acquired biotin deficiency and the two known congenital disorders of biotin metabolism, biotinidase and holocarboxylase synthetase (HCS) deficiency, all lead to deficiency of the 4 biotin-dependent carboxylases, i.e. to multiple carboxylase deficiency (MCD).
    explanation: Review evidence directly supports secondary deficiency of all four biotin-dependent carboxylases in biotinidase deficiency.
  downstream:
  - target: Disrupted intermediary metabolism and organic aciduria
    description: Functional loss of biotin-dependent carboxylases produces toxic metabolite accumulation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body
      explanation: This directly supports the biochemical cascade from carboxylase dysfunction to toxic metabolite accumulation.
- name: Disrupted intermediary metabolism and organic aciduria
  description: 'Functional loss of biotin-dependent carboxylases causes characteristic biochemical derangements including lactic acidosis (pyruvate carboxylase impairment), propionate and methylcitrate accumulation (propionyl-CoA carboxylase impairment), and 3-hydroxyisovalerate accumulation (3-methylcrotonyl-CoA carboxylase impairment).

    '
  mechanism_confidence: ESTABLISHED
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: gluconeogenesis
    term:
      id: GO:0006094
      label: gluconeogenesis
  - preferred_term: propionate catabolic process
    term:
      id: GO:0019543
      label: propionate catabolic process
  - preferred_term: leucine catabolic process
    term:
      id: GO:0006552
      label: L-leucine catabolic process
  molecular_functions:
  - preferred_term: pyruvate carboxylase activity
    term:
      id: GO:0004736
      label: pyruvate carboxylase activity
    modifier: DECREASED
  - preferred_term: propionyl-CoA carboxylase activity
    term:
      id: GO:0004658
      label: propionyl-CoA carboxylase activity
    modifier: DECREASED
  - preferred_term: methylcrotonoyl-CoA carboxylase activity
    term:
      id: GO:0004485
      label: methylcrotonoyl-CoA carboxylase activity
    modifier: DECREASED
  - preferred_term: acetyl-CoA carboxylase activity
    term:
      id: GO:0003989
      label: acetyl-CoA carboxylase activity
    modifier: DECREASED
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine
    explanation: Documents the specific metabolite accumulation pattern in biotinidase deficiency.
  - reference: PMID:24075304
    reference_title: "Biotinidase knockout mice show cellular energy deficit and altered carbon metabolism gene expression similar to that of nutritional biotin deprivation: clues for the pathogenesis in the human inherited disorder."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      a knock-out biotinidase-deficient mouse from a C57BL/6 background that
      was fed a low biotin diet develops severe ATP deficit with activation of
      the energy sensor adenosine monophosphate (AMP)-activated protein kinase
      (AMPK), inhibition of the signaling protein mTOR
    explanation: >-
      The knockout model provides experimental evidence for cellular energy
      stress downstream of biotinidase loss, while extrapolation to each human
      tissue remains incomplete.
  downstream:
  - target: Central nervous system vulnerability and white matter injury
    description: Toxic metabolite buildup and impaired carboxylase activity produce neurologic vulnerability.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Free biotin depletion impairs carboxylase activity needed for energy and organic-acid metabolism.
    evidence:
    - reference: PMID:36759144
      reference_title: "Neuroimaging Features of Biotinidase Deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms
      explanation: Neuroimaging evidence links free biotin deficiency and carboxylase impairment to neurologic manifestations.
  - target: Dermatologic manifestations from systemic biotin depletion
    description: Systemic biotin depletion and impaired fatty-acid metabolism affect skin and mucocutaneous tissues.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Biotin-dependent metabolic disruption affects rapidly renewing cutaneous tissues.
    evidence:
    - reference: PMID:37027963
      reference_title: "Biotinidase deficiency: What have we learned in forty years?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
      explanation: The systematic review quantifies skin involvement downstream of systemic biotinidase deficiency.
  - target: 3-Hydroxyisovalerylcarnitine (C5-OH)
    description: Secondary 3-methylcrotonyl-CoA carboxylase impairment raises plasma C5-OH.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma
      explanation: This directly identifies increased C5-OH downstream of impaired biotin-dependent carboxylase activity.
  - target: 3-Hydroxyisovaleric acid
    description: Secondary leucine-catabolism impairment raises urinary 3-hydroxyisovaleric acid.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine
      explanation: This directly identifies urinary 3-hydroxyisovaleric acid accumulation in BTD deficiency.
  - target: Propionylcarnitine (C3)
    description: Propionyl-CoA carboxylase impairment can elevate C3-acylcarnitine.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Biotin depletion impairs propionyl-CoA carboxylase activity.
    evidence:
    - reference: PMID:38928282
      reference_title: "Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Biotin status/homeostasis in human individuals depends on several factors, including efficiency/deficiency of the enzymes involved in biotin recycling within the human organism (biotinidase, holocarboxylase synthetase)
      explanation: This supports the biotin-recycling defect underlying secondary carboxylase dysfunction, but does not directly name C3.
  - target: Organic aciduria
    description: Multiple carboxylase deficiency produces characteristic urinary organic acid abnormalities.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37027963
      reference_title: "Biotinidase deficiency: What have we learned in forty years?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: characteristic abnormal organic acid metabolites were found in 57.1%
      explanation: The systematic review directly supports organic-acid abnormalities in symptomatic biotinidase deficiency.
  - target: Metabolic acidosis
    description: Accumulation of organic acids and lactate manifests as metabolic acidosis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Impaired carboxylase activity causes organic-acid and lactate accumulation.
    evidence:
    - reference: PMID:37027963
      reference_title: "Biotinidase deficiency: What have we learned in forty years?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: metabolic acidosis was present in 42.4% of symptomatic individuals
      explanation: Directly quantifies metabolic acidosis among symptomatic individuals.
  - target: Metabolic ketoacidosis
    description: Catabolic stress in multiple carboxylase deficiency can produce ketoacidosis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Organic-acid accumulation and impaired intermediary metabolism worsen during catabolism.
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0005979 | Metabolic ketoacidosis | Very frequent (99-80%)"
      explanation: Orphanet supports metabolic ketoacidosis as a very frequent manifestation of biotinidase deficiency.
  - target: Hyperammonemia
    description: Secondary organic-acid accumulation can disrupt nitrogen disposal and produce hyperammonemia.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Propionyl-CoA carboxylase impairment can secondarily inhibit urea-cycle flux.
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001987 | Hyperammonemia | Frequent (79-30%)"
      explanation: Orphanet supports hyperammonemia as a frequent metabolic manifestation.
  - target: Failure to thrive
    description: Chronic metabolic derangement and feeding difficulty impair growth.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
      explanation: Case evidence supports failure to thrive among systemic manifestations of profound biotinidase deficiency.
  - target: Lethargy
    description: Metabolic decompensation can present with lethargy.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001254 | Lethargy | Occasional (29-5%)"
      explanation: Orphanet supports lethargy as an occasional manifestation of biotinidase deficiency.
  - target: Respiratory distress
    description: Systemic metabolic decompensation can include respiratory distress.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0002098 | Respiratory distress | Occasional (29-5%)"
      explanation: Orphanet supports respiratory distress as an occasional manifestation of biotinidase deficiency.
  - target: Apnea
    description: Respiratory involvement during systemic disease can include apnea.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0002104 | Apnea | Occasional (29-5%)"
      explanation: Orphanet supports apnea as an occasional respiratory manifestation.
  - target: Laryngeal stridor
    description: Airway involvement can present as laryngeal stridor.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0006511 | Laryngeal stridor | Occasional (29-5%)"
      explanation: Orphanet supports laryngeal stridor as an occasional manifestation.
- name: Central nervous system vulnerability and white matter injury
  description: 'Neurologic disease in biotinidase deficiency includes white-matter injury. Human imaging has documented cerebellar hypoplasia and leukodystrophy, while the dietary-challenge knockout mouse develops demyelination, axonal degeneration, ventriculomegaly, and corpus callosum compression.

    '
  mechanism_confidence: ESTABLISHED
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  locations:
  - preferred_term: brain white matter
    term:
      id: UBERON:0003544
      label: brain white matter
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  evidence:
  - reference: PMID:36759144
    reference_title: "Neuroimaging Features of Biotinidase Deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups
    explanation: >-
      The multicenter series documents brain imaging abnormalities across age
      groups without specifying individual structures in the cached abstract.
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The brain MRI at 12 months showed cerebellar hypoplasia and multiple foci of leukodystrophy
    explanation: Case demonstrating cerebellar and white matter injury in profound biotinidase deficiency.
  - reference: PMID:22579707
    reference_title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Demyelination, axonal degeneration, ventriculomegaly, and corpus callosum
      compression were found in the brains of untreated, symptomatic
      enzyme-deficient mice.
    explanation: >-
      The knockout model experimentally supports white-matter and axonal injury
      downstream of profound enzyme deficiency.
  - reference: PMID:22579707
    reference_title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Acute biotin deficiency may affect oligodendrocytes and axonal functions
      rather than their viability.
    explanation: >-
      The model authors identify oligodendrocytes as a plausible affected cell
      type; corresponding human cell-type localization remains unresolved.
  downstream:
  - target: Brain imaging abnormality
    description: White-matter and cerebellar abnormalities manifest as abnormal brain imaging.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36759144
      reference_title: "Neuroimaging Features of Biotinidase Deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups
      explanation: Multicenter imaging evidence directly supports brain MRI abnormalities.
  - target: Seizures
    description: CNS vulnerability manifests clinically with seizures.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001250 | Seizure | Frequent (79-30%)"
      explanation: Orphanet supports seizures as a frequent neurologic manifestation of biotinidase deficiency.
  - target: Infantile spasms
    description: Infantile spasms are a seizure phenotype within early CNS involvement.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0012469 | Infantile spasms | Occasional (29-5%)"
      explanation: Orphanet supports infantile spasms as an occasional neurologic manifestation.
  - target: Global developmental delay
    description: Early CNS injury and metabolic vulnerability can impair development.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
      explanation: Psychomotor retardation supports developmental delay downstream of CNS involvement.
  - target: Muscular hypotonia
    description: CNS and motor pathway involvement can manifest with hypotonia.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
      explanation: Case evidence directly lists hypotonia among neurologic manifestations.
  - target: Ataxia
    description: Biotinidase deficiency can manifest with ataxia.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001251 | Ataxia | Occasional (29-5%)"
      explanation: Orphanet supports ataxia as an occasional neurologic manifestation.
  - target: Intellectual disability
    description: Delayed treatment can leave persistent cognitive deficits after CNS injury.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: the therapy failed to show any evident effects on poor feeding and intellectual disability
      explanation: Case evidence supports intellectual disability as a persistent neurologic outcome.
  - target: Spastic paraparesis
    description: Biotinidase deficiency can manifest with spastic paraparesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
      explanation: Orphanet supports spastic paraparesis as an occasional neurologic manifestation.
  - target: Myelopathy
    description: Symptomatic biotinidase deficiency can manifest with myelopathy.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0002196 | Myelopathy | Occasional (29-5%)"
      explanation: Orphanet supports myelopathy as an occasional neurologic manifestation.
  - target: Limb muscle weakness
    description: CNS and motor pathway involvement can manifest with limb muscle weakness.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0003690 | Limb muscle weakness | Occasional (29-5%)"
      explanation: Orphanet supports limb muscle weakness as an occasional neurologic manifestation.
  - target: Sensorineural hearing impairment
    description: Biotinidase deficiency can produce sensorineural hearing impairment.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:39451125
      reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation
      explanation: Cohort evidence supports hearing loss in genetically severe biotinidase deficiency.
  - target: Optic atrophy
    description: Biotinidase deficiency can manifest with optic atrophy.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40190376
      reference_title: "Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Comprehensive ophthalmic examination revealed bilateral optic neuropathy. Laboratory testing showed a biotinidase level of <0.1
      explanation: Case evidence supports optic neuropathy/atrophy in severe biotinidase deficiency.
  - target: Optic neuropathy
    description: Biotinidase deficiency can manifest with optic neuropathy.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001138 | Optic neuropathy | Occasional (29-5%)"
      explanation: Orphanet supports optic neuropathy as an occasional ocular manifestation.
- name: Dermatologic manifestations from systemic biotin depletion
  description: 'Skin rash and alopecia result from disrupted biotin-dependent metabolism affecting rapidly dividing cutaneous tissues. Dermatologic features are among the most common presenting signs of biotinidase deficiency.

    '
  mechanism_confidence: PROVISIONAL
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: fatty acid biosynthetic process
    term:
      id: GO:0006633
      label: fatty acid biosynthetic process
  cell_types:
  - preferred_term: keratinocyte
    term:
      id: CL:0000312
      label: keratinocyte
  locations:
  - preferred_term: skin of body
    term:
      id: UBERON:0002097
      label: skin of body
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Quantifies skin involvement at 53.7% of symptomatic cases in the largest systematic review.
  downstream:
  - target: Skin rash
    description: Cutaneous biotin-dependent metabolic disruption manifests as rash.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0000988 | Skin rash | Frequent (79-30%)"
      explanation: Orphanet supports skin rash as a frequent cutaneous manifestation of biotinidase deficiency.
  - target: Eczematoid dermatitis
    description: Eczematoid dermatitis is a specific cutaneous manifestation of systemic biotin depletion.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0000964 | Eczematoid dermatitis | Occasional (29-5%)"
      explanation: Orphanet supports eczematoid dermatitis as an occasional cutaneous manifestation.
  - target: Alopecia
    description: Impaired skin appendage metabolism can manifest with alopecia.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0001596 | Alopecia | Occasional (29-5%)"
      explanation: Orphanet supports alopecia as an occasional manifestation.
  - target: Recurrent fungal infections
    description: Mucocutaneous vulnerability can manifest as recurrent fungal infections.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0002841 | Recurrent fungal infections | Occasional (29-5%)"
      explanation: Orphanet supports recurrent fungal infections as an occasional mucocutaneous manifestation.
  - target: Conjunctivitis
    description: Ocular surface involvement can manifest as conjunctivitis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      reference_title: "Biotinidase deficiency"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "HP:0000509 | Conjunctivitis | Occasional (29-5%)"
      explanation: Orphanet supports conjunctivitis as an occasional ocular manifestation.
phenotypes:
- name: Seizures
  frequency: FREQUENT
  description: 'Seizures are one of the most common neurological manifestations, occurring as part of the nervous system involvement seen in 67.2% of symptomatic cases. Seizure types may vary and can be the presenting symptom.

    '
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Nervous system involvement at 67.2% supports seizures as a frequent neurological phenotype.
- name: Global developmental delay
  frequency: OCCASIONAL
  description: 'Delayed achievement of developmental milestones occurs in untreated or late-diagnosed biotinidase deficiency, reflecting CNS injury from chronic biotin depletion.

    '
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
    explanation: Case report documents severe psychomotor retardation in a child with profound biotinidase deficiency.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001263 | Global developmental delay | Occasional (29-5%)"
    explanation: Orphanet classifies global developmental delay as occasional in biotinidase deficiency.
- name: Muscular hypotonia
  frequency: FREQUENT
  description: 'Hypotonia is a common early neurological finding in symptomatic biotinidase deficiency, often presenting before seizures or developmental concerns.

    '
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
    explanation: Case report documents hypotonia as a prominent feature in biotinidase deficiency.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%)'
    explanation: Nervous system involvement at 67.2% in the systematic review supports hypotonia as a frequent neurological manifestation.
- name: Alopecia
  frequency: OCCASIONAL
  description: 'Hair loss, often patchy or diffuse, is one of the classic dermatologic features of biotinidase deficiency, reflecting impaired biotin-dependent metabolism in skin appendages.

    '
  phenotype_term:
    preferred_term: Alopecia
    term:
      id: HP:0001596
      label: Alopecia
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Skin involvement at 53.7% includes alopecia; Orphanet classifies alopecia specifically as occasional.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001596 | Alopecia | Occasional (29-5%)"
    explanation: Orphanet classifies alopecia as occasional in biotinidase deficiency.
- name: Skin rash
  frequency: FREQUENT
  description: 'Eczematous or seborrheic dermatitis is a characteristic cutaneous feature, often involving perioral and periorbital regions.

    '
  phenotype_term:
    preferred_term: Skin rash
    term:
      id: HP:0000988
      label: Skin rash
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%)'
    explanation: Skin involvement at 53.7% supports dermatitis as a frequent phenotype.
- name: Sensorineural hearing impairment
  frequency: FREQUENT
  description: 'Sensorineural hearing loss is one of the most clinically significant complications, occurring in approximately 26.9% of symptomatic cases overall but classified as frequent (79-30%) by Orphanet when considering all severity levels. It can be irreversible once established. Early biotin treatment may prevent onset but cannot reverse established hearing loss.

    '
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Auditory involvement at 26.9% supports sensorineural hearing impairment as a significant phenotype.
  - reference: PMID:39451125
    reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation
    explanation: Documents hearing loss in a Turkish cohort and links it to specific BTD variants.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000407 | Sensorineural hearing impairment | Frequent (79-30%)"
    explanation: Orphanet classifies sensorineural hearing impairment as frequent in biotinidase deficiency.
- name: Optic atrophy
  frequency: OCCASIONAL
  description: 'Optic atrophy occurs in a subset of symptomatic cases. Early treatment may halt or reverse the disease process, but delayed diagnosis can result in permanent vision loss.

    '
  phenotype_term:
    preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%)'
    explanation: Eye involvement at 34.4% includes optic atrophy; Orphanet classifies optic atrophy specifically as occasional.
  - reference: PMID:40190376
    reference_title: "Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Comprehensive ophthalmic examination revealed bilateral optic neuropathy. Laboratory testing showed a biotinidase level of <0.1
    explanation: Case report demonstrates bilateral optic neuropathy with improvement after biotin supplementation.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000648 | Optic atrophy | Occasional (29-5%)"
    explanation: Orphanet classifies optic atrophy as occasional in biotinidase deficiency.
- name: Optic neuropathy
  frequency: OCCASIONAL
  description: Optic neuropathy is an occasional ocular manifestation in the Orphanet biotinidase deficiency phenotype table.
  phenotype_term:
    preferred_term: Optic neuropathy
    term:
      id: HP:0001138
      label: Optic neuropathy
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001138 | Optic neuropathy | Occasional (29-5%)"
    explanation: Orphanet provides the disease-phenotype association and frequency band.
- name: Ataxia
  frequency: OCCASIONAL
  description: 'Ataxia can occur in biotinidase deficiency.

    '
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001251 | Ataxia | Occasional (29-5%)"
    explanation: Orphanet classifies ataxia as occasional in biotinidase deficiency.
- name: Metabolic acidosis
  frequency: FREQUENT
  description: 'Metabolic acidosis with lactic acidosis occurs during metabolic decompensation, reflecting impaired pyruvate carboxylase activity and disrupted energy metabolism.

    '
  phenotype_term:
    preferred_term: Metabolic acidosis
    term:
      id: HP:0001942
      label: Metabolic acidosis
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: metabolic acidosis was present in 42.4% of symptomatic individuals
    explanation: Directly quantifies metabolic acidosis frequency at 42.4% in the 1113-case systematic review.
- name: Respiratory distress
  frequency: OCCASIONAL
  description: 'Respiratory distress is an occasional respiratory manifestation of symptomatic biotinidase deficiency and may accompany metabolic decompensation in infants and children.

    '
  phenotype_term:
    preferred_term: Respiratory distress
    term:
      id: HP:0002098
      label: Respiratory distress
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002098 | Respiratory distress | Occasional (29-5%)"
    explanation: Orphanet classifies respiratory distress as occasional in biotinidase deficiency.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Respiratory system involvement at 17.8% supports respiratory involvement broadly; Orphanet provides the specific respiratory distress term.
- name: Intellectual disability
  frequency: OCCASIONAL
  description: 'Intellectual disability can result from delayed diagnosis and treatment. Once established, cognitive deficits may be irreversible despite biotin therapy.

    '
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the therapy failed to show any evident effects on poor feeding and intellectual disability
    explanation: Case report demonstrates that intellectual disability may be irreversible once established despite biotin treatment.
- name: Failure to thrive
  frequency: OCCASIONAL
  description: 'Poor growth and failure to thrive occur in symptomatic children due to metabolic derangement and feeding difficulties.

    '
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive
    explanation: Case report documents failure to thrive as a clinical feature of profound biotinidase deficiency.
- name: Spastic paraparesis
  frequency: OCCASIONAL
  description: 'Spastic paraparesis has been reported in biotinidase deficiency.

    '
  phenotype_term:
    preferred_term: Spastic paraparesis
    term:
      id: HP:0002313
      label: Spastic paraparesis
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
    explanation: Orphanet classifies spastic paraparesis as occasional in biotinidase deficiency.
- name: Myelopathy
  frequency: OCCASIONAL
  description: Myelopathy is an occasional neurologic manifestation recorded for biotinidase deficiency.
  phenotype_term:
    preferred_term: Myelopathy
    term:
      id: HP:0002196
      label: Myelopathy
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002196 | Myelopathy | Occasional (29-5%)"
    explanation: Orphanet provides the disease-phenotype association and frequency band.
- name: Limb muscle weakness
  frequency: OCCASIONAL
  description: Limb muscle weakness is an occasional motor manifestation recorded in the Orphanet biotinidase deficiency phenotype table.
  phenotype_term:
    preferred_term: Limb muscle weakness
    term:
      id: HP:0003690
      label: Limb muscle weakness
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0003690 | Limb muscle weakness | Occasional (29-5%)"
    explanation: Orphanet provides the disease-phenotype association and frequency band.
- name: Hyperammonemia
  frequency: FREQUENT
  description: 'Elevated blood ammonia levels occur during metabolic decompensation. The mechanism involves propionyl-CoA carboxylase impairment leading to propionyl-CoA accumulation, which inhibits N-acetylglutamate synthase (NAGS), impairing carbamyl phosphate synthetase 1 (CPS1) and thereby disrupting the urea cycle. Hyperammonemia can contribute to encephalopathy.

    '
  phenotype_term:
    preferred_term: Hyperammonemia
    term:
      id: HP:0001987
      label: Hyperammonemia
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001987 | Hyperammonemia | Frequent (79-30%)"
    explanation: Orphanet classifies hyperammonemia as frequent in biotinidase deficiency.
- name: Organic aciduria
  frequency: VERY_FREQUENT
  description: 'Elevated urinary organic acids, including 3-hydroxyisovaleric acid, 3-methylcrotonylglycine, methylcitrate, and lactate, are characteristic metabolic markers reflecting impaired biotin-dependent carboxylase function.

    '
  phenotype_term:
    preferred_term: Organic aciduria
    term:
      id: HP:0001992
      label: Organic aciduria
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: characteristic abnormal organic acid metabolites were found in 57.1%
    explanation: Systematic review found organic aciduria in 57.1% of symptomatic cases when tested; frequency is VERY_FREQUENT per Orphanet, reflecting expected biochemical abnormality in untreated disease.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001992 | Organic aciduria | Very frequent (99-80%)"
    explanation: Orphanet is the authoritative frequency source here; the lower PMID figure reflects incomplete metabolic workups in a heterogeneous cohort.
- name: Metabolic ketoacidosis
  frequency: VERY_FREQUENT
  description: 'Ketoacidosis results from impaired carboxylase-dependent intermediary metabolism, particularly during catabolic stress. It is one of the most consistent metabolic findings in untreated biotinidase deficiency.

    '
  phenotype_term:
    preferred_term: Metabolic ketoacidosis
    term:
      id: HP:0005979
      label: Metabolic ketoacidosis
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: metabolic acidosis was present in 42.4% of symptomatic individuals
    explanation: The systematic review supports metabolic acidosis broadly; Orphanet provides the specific metabolic ketoacidosis support.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0005979 | Metabolic ketoacidosis | Very frequent (99-80%)"
    explanation: Orphanet classifies metabolic ketoacidosis as very frequent in biotinidase deficiency.
- name: Eczematoid dermatitis
  frequency: OCCASIONAL
  description: 'Eczematous or seborrheic dermatitis affecting perioral, periorbital, and diaper regions is a characteristic cutaneous finding distinct from generalized skin rash.

    '
  phenotype_term:
    preferred_term: Eczematoid dermatitis
    term:
      id: HP:0000964
      label: Eczematoid dermatitis
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%)'
    explanation: Skin involvement at 53.7% includes eczematoid dermatitis as a specific presentation.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000964 | Eczematoid dermatitis | Occasional (29-5%)"
    explanation: Orphanet classifies eczematoid dermatitis as occasional in biotinidase deficiency.
- name: Lethargy
  frequency: OCCASIONAL
  description: 'Lethargy and decreased arousal can occur during metabolic decompensation or as part of progressive encephalopathy in untreated cases.

    '
  phenotype_term:
    preferred_term: Lethargy
    term:
      id: HP:0001254
      label: Lethargy
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001254 | Lethargy | Occasional (29-5%)"
    explanation: Orphanet classifies lethargy as occasional in biotinidase deficiency.
- name: Apnea
  frequency: OCCASIONAL
  description: 'Apneic episodes occur as part of respiratory system involvement, particularly in neonatal and early childhood-onset presentations.

    '
  phenotype_term:
    preferred_term: Apnea
    term:
      id: HP:0002104
      label: Apnea
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%)'
    explanation: Respiratory system involvement at 17.8% includes apneic episodes.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002104 | Apnea | Occasional (29-5%)"
    explanation: Orphanet classifies apnea as occasional in biotinidase deficiency.
- name: Laryngeal stridor
  frequency: OCCASIONAL
  description: 'Stridor from laryngeal involvement can be a presenting respiratory symptom, particularly in infants with biotinidase deficiency.

    '
  phenotype_term:
    preferred_term: Laryngeal stridor
    term:
      id: HP:0006511
      label: Laryngeal stridor
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0006511 | Laryngeal stridor | Occasional (29-5%)"
    explanation: Orphanet classifies laryngeal stridor as occasional in biotinidase deficiency.
- name: Recurrent fungal infections
  frequency: OCCASIONAL
  description: 'Immune dysfunction in biotinidase deficiency manifests as susceptibility to fungal and candidal infections, likely reflecting impaired T-cell and B-cell function secondary to biotin depletion.

    '
  phenotype_term:
    preferred_term: Recurrent fungal infections
    term:
      id: HP:0002841
      label: Recurrent fungal infections
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002841 | Recurrent fungal infections | Occasional (29-5%)"
    explanation: Orphanet classifies recurrent fungal infections as occasional in biotinidase deficiency.
- name: Conjunctivitis
  frequency: OCCASIONAL
  description: 'Conjunctivitis is among the ocular manifestations of biotinidase deficiency, contributing to the 34.4% eye involvement rate documented in symptomatic cases.

    '
  phenotype_term:
    preferred_term: Conjunctivitis
    term:
      id: HP:0000509
      label: Conjunctivitis
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%)'
    explanation: Eye involvement at 34.4% includes conjunctivitis as a specific presentation.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0000509 | Conjunctivitis | Occasional (29-5%)"
    explanation: Orphanet classifies conjunctivitis as occasional in biotinidase deficiency.
- name: Brain imaging abnormality
  frequency: FREQUENT
  description: 'Brain MRI abnormalities are documented across age groups in symptomatic biotinidase deficiency.

    '
  phenotype_term:
    preferred_term: Brain imaging abnormality
    term:
      id: HP:0410263
      label: Brain imaging abnormality
  evidence:
  - reference: PMID:36759144
    reference_title: "Neuroimaging Features of Biotinidase Deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups
    explanation: Multicenter neuroimaging study documenting characteristic brain MRI patterns.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0410263 | Brain imaging abnormality | Frequent (79-30%)"
    explanation: Orphanet classifies brain imaging abnormality as frequent in biotinidase deficiency.
- name: Infantile spasms
  frequency: OCCASIONAL
  description: 'Infantile spasms (West syndrome) have been reported as a seizure type in neonatal and early infantile-onset biotinidase deficiency presentations.

    '
  phenotype_term:
    preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  evidence:
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0012469 | Infantile spasms | Occasional (29-5%)"
    explanation: Orphanet classifies infantile spasms as occasional in biotinidase deficiency.
- name: Decreased biotinidase activity
  frequency: VERY_FREQUENT
  description: 'Reduced serum biotinidase enzyme activity is the hallmark diagnostic marker. Profound deficiency is defined as less than 10% of mean normal activity and partial deficiency as 10-30%.

    '
  phenotype_term:
    preferred_term: Decreased biotinidase activity
    term:
      id: HP:0410145
      label: Decreased circulating biotinidase concentration
  evidence:
  - reference: PMID:38141137
    reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%
    explanation: Large cohort quantifies the distribution of enzyme deficiency severity categories.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0410145 | Decreased biotinidase activity | Very frequent (99-80%)"
    explanation: Orphanet classifies decreased biotinidase activity as very frequent (diagnostic hallmark).
biochemical:
- name: 3-Hydroxyisovalerylcarnitine (C5-OH)
  presence: INCREASED
  context: 'Elevated C5-OH acylcarnitine is a characteristic plasma marker of impaired leucine catabolism via 3-methylcrotonyl-CoA carboxylase deficiency. Detectable on newborn screening acylcarnitine profiles.

    '
  readouts:
  - target: Disrupted intermediary metabolism and organic aciduria
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated C5-OH reports secondary multiple-carboxylase dysfunction and the leucine-catabolism branch of the metabolic block.
    evidence:
    - reference: PMID:33572391
      reference_title: "Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: increased levels of C5OH may be linked to 3-methylcrotonyl-CoA carboxylase activity
      explanation: This human newborn-screening report explicitly links C5OH elevation to the 3-methylcrotonyl-CoA carboxylase branch affected by BTD deficiency.
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma
    explanation: Directly identifies elevated C5-OH as a primary plasma marker.
- name: 3-Hydroxyisovaleric acid
  presence: INCREASED
  context: 'Elevated urinary 3-hydroxyisovaleric acid is a characteristic organic acid marker reflecting impaired leucine catabolism via 3-methylcrotonyl-CoA carboxylase.

    '
  readouts:
  - target: Disrupted intermediary metabolism and organic aciduria
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated urinary 3-hydroxyisovaleric acid reports impaired 3-methylcrotonyl-CoA carboxylase-dependent leucine catabolism.
    evidence:
    - reference: PMID:37373384
      reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine
      explanation: This case report directly identifies urinary 3-hydroxyisovaleric acid accumulation downstream of impaired BTD-dependent carboxylase function.
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine
    explanation: Directly identifies elevated urinary 3-hydroxyisovaleric acid as a characteristic marker.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: characteristic abnormal organic acid metabolites were found in 57.1%
    explanation: Confirms organic acid abnormalities in the majority of symptomatic cases.
- name: Propionylcarnitine (C3)
  presence: INCREASED
  context: 'Elevated C3-acylcarnitine reflects propionyl-CoA carboxylase dysfunction in the setting of secondary multiple carboxylase deficiency.

    '
  readouts:
  - target: Disrupted intermediary metabolism and organic aciduria
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated C3 reports the propionyl-CoA carboxylase branch of secondary multiple-carboxylase dysfunction.
    evidence:
    - reference: PMID:33572391
      reference_title: "Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: mildly elevated C3 levels may reflect propionyl-CoA carboxylase deficiency
      explanation: This human newborn-screening report directly links C3 elevation to propionyl-CoA carboxylase deficiency in the BTD deficiency metabolic context.
  evidence:
  - reference: PMID:33572391
    reference_title: "Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: mildly elevated C3 levels may reflect propionyl-CoA carboxylase deficiency
    explanation: Directly supports C3 elevation as a marker of the propionyl-CoA carboxylase branch in biotinidase deficiency.
  - reference: PMID:38928282
    reference_title: "Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Biotin status/homeostasis in human individuals depends on several factors, including efficiency/deficiency of the enzymes involved in biotin recycling within the human organism (biotinidase, holocarboxylase synthetase)
    explanation: Review supports impaired biotin recycling and downstream carboxylase dysfunction, but does not directly name C3 propionylcarnitine.
- name: Lactate
  presence: INCREASED
  context: 'Lactic acidosis results from pyruvate carboxylase impairment. Brain lactate may be detectable by magnetic resonance spectroscopy.

    '
  readouts:
  - target: Disrupted intermediary metabolism and organic aciduria
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Lactate elevation reports impaired pyruvate carboxylase-dependent intermediary metabolism and lactic-acidosis risk.
    evidence:
    - reference: PMID:9427142
      reference_title: "Cerebral metabolic changes in biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Lactate, pyruvate and 3-hydroxyisovaleric acid as metabolic disease markers were measured in blood, cerebrospinal fluid and brain tissue by biochemical analyses or localized magnetic resonance proton spectroscopy.
      explanation: Human metabolic imaging and biochemical measurements identify lactate as a disease marker in biotinidase deficiency.
  evidence:
  - reference: PMID:9427142
    reference_title: "Cerebral metabolic changes in biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Lactate, pyruvate and 3-hydroxyisovaleric acid as metabolic disease markers were measured in blood, cerebrospinal fluid and brain tissue by biochemical analyses or localized magnetic resonance proton spectroscopy.
    explanation: Directly supports lactate as a biochemical disease marker in biotinidase deficiency.
  - reference: PMID:3736876
    reference_title: "Biotinidase deficiency: accumulation of lactate in the brain and response to physiologic doses of biotin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: this disorder who had high CSF content of lactate that could have contributed to the clinical disorder
    explanation: Classic patient report supports increased CSF lactate in biotinidase deficiency.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: metabolic acidosis was present in 42.4% of symptomatic individuals
    explanation: Metabolic acidosis in biotinidase deficiency includes lactic acidosis from pyruvate carboxylase dysfunction.
- name: Biotinidase enzyme activity
  presence: DECREASED
  context: 'Reduced serum biotinidase enzyme activity is the definitive diagnostic marker. Profound deficiency is defined as less than 10% of mean normal activity and partial deficiency as 10-30%.

    '
  readouts:
  - target: Impaired biotin recycling
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Reduced biotinidase activity directly reports the proximal BTD enzyme defect that impairs biotin recycling.
    evidence:
    - reference: PMID:38141137
      reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%
      explanation: Cohort enzyme-activity data support reduced biotinidase activity as the diagnostic readout of the proximal mechanism.
  evidence:
  - reference: PMID:40190376
    reference_title: "Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Laboratory testing showed a biotinidase level of <0.1 (normal, 5.5-10 nmol/min/ml)
    explanation: Case report documents severely reduced biotinidase activity confirming the diagnosis.
  - reference: PMID:38141137
    reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Complete enzyme deficiency was identified in 19.8%, partial enzyme deficiency in 55.1%, and heterogenous enzyme deficiency in 9.7%
    explanation: Large cohort quantifies the distribution of enzyme deficiency severity categories.
genetic:
- name: BTD gene variants causing biotinidase deficiency
  gene_term:
    preferred_term: BTD
    term:
      id: hgnc:1122
      label: BTD
  variants:
  - name: c.1270G>C (p.Asp424His)
    description: >-
      This was the most frequent BTD variant in two Turkish cohorts. In one
      cohort, 97.3% of homozygotes had enzyme activity above 30%, so this
      genotype should not be equated automatically with biochemical partial
      deficiency without an activity assay. The cited studies use p.Asp424His;
      cross-cohort comparison requires normalization to a specified reference
      transcript and protein sequence. Regional frequency should not be
      generalized worldwide.
    evidence:
    - reference: PMID:39451125
      reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: the most frequent variant was c.1270G > C | p.Asp424His. Biotinidase enzyme activity was above 30% in 97.3% of patients with a homozygous p.D424His mutation
      explanation: >-
        The regional cohort identifies D424H as frequent and, importantly,
        documents activity above the partial-deficiency range in most
        homozygotes.
    - reference: PMID:38141137
      reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The most common pathogenic variants were c.1270G > C (p.Asp424His), c.410G > A (p.Arg137His), and c.38_44delGCGCTGinsTCC (p.Cys13Phefs*36) in BTD gene
      explanation: Confirms D424H as the most common variant in a large Turkish cohort.
  - name: c.410G>A (p.Arg137His)
    description: >-
      This variant was among those associated with the largest enzyme-activity
      decreases and was enriched among neurologically symptomatic individuals
      in regional cohorts. Those associations are not deterministic for an
      individual patient.
    evidence:
    - reference: PMID:39451125
      reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The mutations that caused the most significant decrease in enzyme activity were c.410G > A p.Arg137His, c.38_delinsTCC p.Cys13phefs*36, and c.1535C > T p.Thr512Met
      explanation: Identifies R137H as causing significant enzyme activity reduction.
    - reference: PMID:38141137
      reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The c.410G > A and c.38_44delGCGCTGinsTCC variants were more common in the patients with neurological symptoms
      explanation: Links R137H variant to neurological presentation.
  - name: c.38_44delGCGCTGinsTCC (p.Cys13Phefs*36)
    description: >-
      This frameshift was associated with marked enzyme-activity reduction,
      neurologic manifestations, hearing loss, and optic atrophy in regional
      cohorts. The small numbers and inclusion of both homozygous and
      heterozygous observations limit individual prognostic prediction.
    evidence:
    - reference: PMID:39451125
      reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation (homozygous or heterozygous)
      explanation: Links this frameshift variant to severe sensory complications.
    - reference: PMID:38141137
      reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The c.410G > A and c.38_44delGCGCTGinsTCC variants were more common in the patients with neurological symptoms
      explanation: Confirms association of this variant with neurological symptoms in a large cohort.
  features: >-
    Biallelic pathogenic BTD variants reduce biotinidase enzyme activity.
    Clinical classification is anchored to measured residual enzyme activity:
    profound deficiency is below 10% and partial deficiency is 10%-30% of mean
    normal activity. Regional genotype-phenotype associations can support
    interpretation but do not replace biochemical confirmation.
  evidence:
  - reference: PMID:38141137
    reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Two hundred forty-seven cases were included in the study who were admitted to the Department of Pediatric Metabolism
    explanation: Large cohort study providing comprehensive genotype-phenotype correlations in biotinidase deficiency.
  - reference: PMID:39451125
    reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This study provides a detailed analysis of genetic diversity and clinical presentation in biotinidase deficiency cases in Eastern Anatolia, demonstrating the efficacy of biotin treatment
    explanation: Regional cohort study demonstrating genetic diversity and variant-phenotype relationships.
  - reference: ORPHA:79241
    reference_title: "Biotinidase deficiency"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "BTD | biotinidase | hgnc:1122 | Disease-causing germline mutation(s) in"
    explanation: Orphanet confirms BTD as the disease-causing gene for biotinidase deficiency.
  - reference: CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z
    reference_title: "BTD / biotinidase deficiency (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "BTD | HGNC:1122 | biotinidase deficiency | MONDO:0009665 | AR | Definitive"
    explanation: ClinGen classifies the BTD-biotinidase deficiency gene-disease relationship as definitive with autosomal recessive inheritance.
diagnosis:
- name: Serum or plasma biotinidase enzyme-activity assay
  description: >-
    Quantitative measurement of biotinidase activity in serum or plasma is the
    primary confirmatory biochemical test. Residual activity classifies
    profound deficiency below 10% and partial deficiency at 10%-30% of mean
    normal activity.
  diagnosis_term:
    preferred_term: diagnostic procedure
    term:
      id: NCIT:C18020
      label: Diagnostic Procedure
  markers: Biotinidase enzyme activity
  results: >-
    Deficient serum or plasma activity confirms the proximal enzyme defect and
    supplies the biochemical severity classification.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: detection of deficient biotinidase enzyme activity in serum/plasma
    explanation: >-
      Current GeneReviews identifies deficient serum/plasma enzyme activity as
      a diagnostic route.
- name: BTD molecular genetic testing
  description: >-
    Identification of biallelic pathogenic BTD variants establishes the
    molecular diagnosis and is particularly useful when enzyme results are
    ambiguous. Enzyme activity remains important for severity classification.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  results: Biallelic pathogenic BTD variants support the molecular diagnosis.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      identification of biallelic pathogenic variants in BTD on molecular
      genetic testing when the results of enzymatic testing are ambiguous.
    explanation: >-
      Current GeneReviews defines molecular testing as a diagnostic route when
      enzyme testing is ambiguous.
- name: Newborn screening for biotinidase deficiency
  description: >-
    Newborn screening identifies affected infants before symptoms and should be
    followed by confirmatory serum/plasma enzyme activity testing, with
    molecular testing when biochemical results are ambiguous.
  diagnosis_term:
    preferred_term: disease screening
    term:
      id: NCIT:C15419
      label: Disease Screening
  results: >-
    A low screening biotinidase activity result triggers confirmatory
    biochemical and, when needed, molecular testing.
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Newborn screening has had a major positive impact on the outcome of many individuals with BD
    explanation: >-
      The 1,113-person systematic review supports the clinical utility of
      newborn screening.
  - reference: PMID:38141137
    reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: An analysis of the admission routes of all cases to our clinic revealed 89.5% NBS, 5.7% family screening, and 4.9% suspicious clinical findings suggestive of BD
    explanation: >-
      A 247-person cohort shows that screening was the predominant diagnostic
      route.
differential_diagnoses:
- name: Holocarboxylase synthetase deficiency
  disease_term:
    preferred_term: holocarboxylase synthetase deficiency
    term:
      id: MONDO:0009666
      label: holocarboxylase synthetase deficiency
  description: >-
    HLCS deficiency is the other inherited cause of multiple carboxylase
    deficiency. Direct biotinidase activity and BTD/HLCS molecular testing
    distinguish these disorders when metabolites indicate multiple carboxylase
    dysfunction.
  evidence:
  - reference: PMID:9350481
    reference_title: "Multiple carboxylase deficiency: inherited and acquired disorders of biotin metabolism."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      the two known congenital disorders of biotin metabolism, biotinidase and
      holocarboxylase synthetase (HCS) deficiency, all lead to deficiency of the
      4 biotin-dependent carboxylases
    explanation: >-
      The review identifies biotinidase and holocarboxylase synthetase
      deficiency as distinct inherited routes to the same biochemical pattern.
treatments:
- name: Oral biotin supplementation
  description: >-
    Lifelong oral free biotin is the disease-specific therapy for both profound
    and partial deficiency. Current GeneReviews dosing is 5-10 mg/day for
    profound deficiency and 2.5-10 mg/day for partial deficiency.
    Presymptomatic adherence prevents manifestations; established hearing loss,
    optic atrophy, or developmental impairment may not completely reverse.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: biotin
      term:
        id: CHEBI:15956
        label: biotin
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  - preferred_term: Metabolic acidosis
    term:
      id: HP:0001942
      label: Metabolic acidosis
  - preferred_term: Organic aciduria
    term:
      id: HP:0001992
      label: Organic aciduria
  - preferred_term: Skin rash
    term:
      id: HP:0000988
      label: Skin rash
  - preferred_term: Alopecia
    term:
      id: HP:0001596
      label: Alopecia
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All individuals with profound biotinidase deficiency (<10% mean normal
      serum enzyme activity) and those with partial biotinidase deficiency
      (10%-30% of mean normal serum enzyme activity) should be treated with oral
      biotin in the free form as opposed to the protein-bound form; biotin
      therapy is lifelong.
    explanation: >-
      Current GeneReviews recommends lifelong oral free biotin for both
      biochemical severity classes.
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Oral biotin of 5-10 mg/day for those who have <10% mean normal serum
      enzyme activity and 2.5-10 mg/day in those who have 10%-30% of mean
      normal serum enzyme activity.
    explanation: Current GeneReviews supplies severity-specific dose ranges.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Biotin treatment led to clinical stability or improvement in 89.2% of individuals. 1.6% of reported individuals with BD died due to non-availability of treatment or late diagnosis
    explanation: Systematic review of 1113 cases demonstrating high efficacy of biotin treatment.
  - reference: PMID:40190376
    reference_title: "Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patient was treated with oral biotin supplementation with improvement in her visual function
    explanation: Case demonstrating biotin supplementation improving visual function in an adult patient.
  target_mechanisms:
  - target: Impaired biotin recycling
    treatment_effect: BYPASSES
    description: Pharmacologic free biotin supplementation bypasses defective biotin recycling and restores biotin availability for carboxylase biotinylation.
    evidence:
    - reference: PMID:37027963
      reference_title: "Biotinidase deficiency: What have we learned in forty years?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Biotin treatment led to clinical stability or improvement in 89.2% of individuals.
      explanation: Treatment-response evidence supports free biotin supplementation as the disease-modifying intervention.
  - target: Disrupted intermediary metabolism and organic aciduria
    treatment_effect: RESTORES
    description: Providing free biotin restores downstream biotin-dependent carboxylase function and reduces metabolic instability.
    evidence:
    - reference: PMID:38928282
      reference_title: "Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: administration of biotin at high/"pharmacological" doses has been proposed to treat specific defects/deficiencies and human disorders
      explanation: Review evidence supports pharmacologic biotin as treatment for biotin-homeostasis defects.
  review_notes: >-
    Most outcome evidence is observational because newborn screening and the
    large treatment effect make untreated comparison groups neither common nor
    appropriate. Improvement of an established sensory deficit in a case report
    does not imply reliable reversibility for all patients.
- name: Antiseizure medication
  description: 'Anticonvulsant therapy may be needed for seizure management, although seizures often resolve with biotin supplementation alone. Antiepileptic therapy alone without biotin is typically insufficient.

    '
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: antiepileptic drug therapy
    term:
      id: NCIT:C64172
      label: Anticonvulsant Therapy
  target_phenotypes:
  - preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:37373384
    reference_title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The result of antiepileptic therapy was not satisfying
    explanation: Case demonstrates that antiepileptic therapy alone is insufficient and biotin is the essential treatment.
- name: Genetic counseling
  description: 'Genetic counseling is recommended for affected families to discuss autosomal recessive inheritance, 25% recurrence risk, carrier testing, and prenatal/preimplantation genetic testing options.

    '
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      each sib of an affected individual has at conception a 25% chance of
      being affected, a 50% chance of being an asymptomatic carrier, and a 25%
      chance of being unaffected and not a carrier.
    explanation: Current GeneReviews provides the autosomal-recessive recurrence risks used in counseling.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Biotinidase deficiency (BD) is an autosomal recessively inherited disorder
    explanation: Autosomal recessive inheritance pattern supports the role of genetic counseling.
  - reference: PMID:38141137
    reference_title: "Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Biotinidase deficiency (BD) is an autosomal recessive inherited metabolic disorder
    explanation: Genetic basis of the disorder supports counseling for recurrence risk assessment.
- name: Supportive care
  description: >-
    Symptomatic metabolic decompensation may require hydration and bicarbonate
    while biotin corrects the underlying derangement. Developmental,
    educational, ophthalmologic, and audiologic support address residual
    complications.
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Metabolic acidosis
    term:
      id: HP:0001942
      label: Metabolic acidosis
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  - preferred_term: Optic atrophy
    term:
      id: HP:0000648
      label: Optic atrophy
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hydration and bicarbonate in those with metabolic decompensation and
      acidosis, although biotin therapy can rapidly resolve the metabolic
      derangements within hours to days
    explanation: Current GeneReviews supports acute hydration and bicarbonate while disease-specific therapy takes effect.
- name: Audiological management
  description: 'Regular audiological assessment and hearing aid or cochlear implant consideration for patients with sensorineural hearing loss, which may be irreversible once established.

    '
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: hearing aids and, if severe, consideration of cochlear implants for those with hearing loss.
    explanation: Current GeneReviews directly supports hearing aids and cochlear-implant consideration.
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%)'
    explanation: Auditory involvement at 26.9% supports the need for audiological monitoring and management.
  - reference: PMID:39451125
    reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hearing loss (4 patients) and optic atrophy (1 patient) were mainly observed in patients with the c.38_delinsTCC mutation
    explanation: Documents hearing loss as a significant complication requiring audiological management.
- name: Avoidance of raw egg white
  description: >-
    Raw egg white contains avidin, which binds biotin and reduces its
    bioavailability. Thorough cooking inactivates avidin.
  role: Agent or circumstance to avoid
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Raw eggs should be avoided because they contain avidin, an egg white
      protein that binds biotin, thus decreasing its bioavailability.
    explanation: Current GeneReviews explicitly identifies raw eggs as a circumstance to avoid.
animal_models:
- species: Mus musculus
  genotype: Homozygous Btd null allele (Btd-/-)
  background: >-
    Congenic C57BL/6 background after ten backcross generations; animals remain
    asymptomatic on a biotin-replete standard diet and develop disease
    manifestations after a low- or biotin-deficient dietary challenge.
  category: Knockout, dietary challenge, and biotin rescue
  description: >-
    Btd-null mice lack detectable serum biotinidase activity. A
    biotin-deficient diet produces neurologic and cutaneous disease, secondary
    carboxylase deficiency, organic-acid abnormalities, and white-matter/axonal
    injury; pharmacologic biotin reverses many measured manifestations. The
    required dietary challenge is an important boundary on direct comparison
    with untreated human disease.
  associated_phenotypes:
  - Absent serum biotinidase activity
  - Neurological deficits
  - Cutaneous abnormalities and alopecia
  - Secondary carboxylase deficiency
  - Demyelination and axonal degeneration
  - Increased urinary 3-hydroxyisovaleric acid
  evidence:
  - reference: PMID:21051254
    reference_title: "Development and characterization of a mouse with profound biotinidase deficiency: a biotin-responsive neurocutaneous disorder."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The mouse has a null mutation that results in no detectable serum
      biotinidase activity or cross-reacting material to antibody prepared
      against biotinidase.
    explanation: The model publication directly defines the null genotype and enzyme phenotype.
  - reference: PMID:21051254
    reference_title: "Development and characterization of a mouse with profound biotinidase deficiency: a biotin-responsive neurocutaneous disorder."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      When fed a biotin-deficient diet these mice develop neurological and
      cutaneous symptoms, carboxylase deficiency, mild hyperammonemia, and
      exhibit increased urinary excretion of 3-hydroxyisovaleric acid and biotin
      and biotin metabolites.
    explanation: >-
      The dietary-challenge experiment directly documents the neurocutaneous
      and biochemical disease phenotype.
  - reference: PMID:22579707
    reference_title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      the chimera with the gene knock-out was generated followed by initial
      backcross with C57BL/6 background mouse for 10 generations to obtain the
      biotinidase gene knock-out mouse with C57BL/6 genetic background.
    explanation: The model publication directly documents the congenic C57BL/6 background.
  - reference: PMID:22579707
    reference_title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      With biotin treatment, the symptomatic mice improved neurologically and
      the white matter abnormalities resolved.
    explanation: The rescue experiment supports biotin responsiveness of measured neurologic and white-matter abnormalities.
discussions:
- discussion_id: gap_human_sensory_injury_reversibility
  prompt: >-
    Which cellular events determine whether auditory, optic, and developmental
    injury remains reversible after biotin is started?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Central nervous system vulnerability and white matter injury
  - treatments#Oral biotin supplementation
  - animal_models#Mus musculus
  rationale: >-
    The knockout mouse shows rapid neurologic, myelin, and axonal recovery after
    biotin, whereas established hearing loss, optic atrophy, and developmental
    impairment in humans are commonly incomplete responders. The temporal and
    cell-type-specific transition to irreversible injury is not resolved by
    either evidence base.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      optic atrophy, hearing loss, and developmental delay, may improve but are
      usually not completely reversible with the initiation of biotin therapy.
    explanation: Current GeneReviews documents the human residual-injury boundary.
  - reference: PMID:22579707
    reference_title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      With biotin treatment, the symptomatic mice improved neurologically and
      the white matter abnormalities resolved.
    explanation: The mouse rescue exposes the difference from commonly persistent human sensory injury.
- discussion_id: gap_partial_deficiency_natural_history
  prompt: >-
    What is the untreated lifetime penetrance and stress-specific risk of
    biochemically confirmed partial biotinidase deficiency?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - has_subtypes#Partial biotinidase deficiency
  - treatments#Oral biotin supplementation
  rationale: >-
    Lifelong free biotin is the current recommendation and should not be
    withheld. However, widespread presymptomatic screening and treatment leave
    limited direct observation of the untreated partial-deficiency natural
    history, including which infections or physiologic stresses precipitate
    disease.
  evidence:
  - reference: PMID:20301497
    reference_title: Biotinidase Deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Individuals with partial biotinidase deficiency (10%-30% of mean normal
      serum biotinidase activity) may develop symptoms only when stressed, such
      as during infection.
    explanation: Current GeneReviews identifies stress-related expression without quantifying lifetime penetrance.
- discussion_id: gap_genotype_activity_classification
  prompt: >-
    How should transcript-specific BTD variant nomenclature and regional
    genotype associations be reconciled with measured enzyme-activity classes?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - genetic#BTD gene variants causing biotinidase deficiency
  - diagnosis#Serum or plasma biotinidase enzyme-activity assay
  rationale: >-
    Severity is defined biochemically, while published cohorts use different
    variant numbering and show that a frequent homozygous genotype can retain
    activity above the partial-deficiency range. Harmonized transcript
    nomenclature and assay-aware interpretation are needed before using
    regional genotype associations prognostically.
  evidence:
  - reference: PMID:39451125
    reference_title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Biotinidase enzyme activity was above 30% in 97.3% of patients with a
      homozygous p.D424His mutation
    explanation: >-
      The cohort demonstrates why genotype alone cannot substitute for the
      biochemical severity threshold.
references:
- reference: PMID:20301497
  title: Biotinidase Deficiency.
  tags:
  - GeneReviews
  findings: []
- reference: ORPHA:79241
  title: Biotinidase deficiency
  findings: []
- reference: CGGV:assertion_847f7f2b-575f-4a90-bf02-179d464e4841-2020-02-10T180000.000Z
  title: BTD / biotinidase deficiency (Definitive)
  findings: []
- reference: PMID:1779651
  title: Worldwide survey of neonatal screening for biotinidase deficiency.
  findings: []
- reference: PMID:2314964
  title: "Screening for biotinidase deficiency in newborns: worldwide experience."
  findings: []
- reference: PMID:9713119
  title: "[Prevalence study of biotinidase deficiency in newborns]."
  findings: []
- reference: PMID:33572391
  title: Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening.
  findings: []
- reference: PMID:36759144
  title: Neuroimaging Features of Biotinidase Deficiency.
  findings: []
- reference: PMID:37027963
  title: "Biotinidase deficiency: What have we learned in forty years?"
  findings: []
- reference: PMID:3736876
  title: "Biotinidase deficiency: accumulation of lactate in the brain and response to physiologic doses of biotin."
  findings: []
- reference: PMID:37373384
  title: "Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking."
  findings: []
- reference: PMID:38141137
  title: Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency.
  findings: []
- reference: PMID:38928282
  title: "Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives."
  findings: []
- reference: PMID:39451125
  title: "A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort."
  findings: []
- reference: PMID:40190376
  title: "Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review."
  findings: []
- reference: PMID:9350481
  title: "Multiple carboxylase deficiency: inherited and acquired disorders of biotin metabolism."
  findings: []
- reference: PMID:9427142
  title: Cerebral metabolic changes in biotinidase deficiency.
  findings: []
- reference: PMID:21051254
  title: "Development and characterization of a mouse with profound biotinidase deficiency: a biotin-responsive neurocutaneous disorder."
  findings: []
- reference: PMID:22579707
  title: Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
  findings: []
- reference: PMID:24075304
  title: "Biotinidase knockout mice show cellular energy deficit and altered carbon metabolism gene expression similar to that of nutritional biotin deprivation: clues for the pathogenesis in the human inherited disorder."
  findings: []
review_notes: >-
  This entry is scoped to biallelic BTD-related biotinidase deficiency;
  holocarboxylase synthetase deficiency is a distinct inherited cause of
  multiple carboxylase deficiency. Profound and partial disease are
  biochemical residual-activity classes rather than genotype-defined subtypes;
  no distinct MONDO concepts were found for these classes, so subtype_term is
  intentionally omitted. Regional variant associations were retained only with
  cohort boundaries and do not replace enzyme testing. Orphanet frequencies
  describe the disease concept and should not be interpreted as frequencies
  among newborn-screened, presymptomatically treated individuals. The D2P
  audit surfaced additional findings such as diarrhea, hepatosplenomegaly, and
  more specific seizure or imaging terms; these were not bulk-imported without
  exact local evidence or where a broader supported phenotype was already
  present. Red-nucleus, Purkinje-cell, and auditory-brainstem localization
  mentioned in the research synthesis was not modeled because no exact
  quotable source text was available in the local reference cache.
  HP:0410145 is the closest available HPO mapping for decreased circulating
  biotinidase, but its label describes concentration while the diagnostic
  evidence measures enzyme activity; preferred_term therefore preserves
  "Decreased biotinidase activity," and a dedicated HPO activity term may
  warrant a future term request. No public disease-specific omics or phenotype
  dataset accession was identified in GEO, and no validated non-animal disease
  model was found, so datasets and experimental_models are intentionally
  omitted. Treatment outcome evidence is principally observational, but
  current guidance recommends lifelong oral free biotin for both profound and
  partial deficiency.
📚

References & Deep Research

References

20
PMID:20301497
Biotinidase Deficiency.
No top-level findings curated for this source.
ORPHA:79241
Biotinidase deficiency
No top-level findings curated for this source.
No top-level findings curated for this source.
PMID:1779651
Worldwide survey of neonatal screening for biotinidase deficiency.
No top-level findings curated for this source.
PMID:2314964
Screening for biotinidase deficiency in newborns: worldwide experience.
No top-level findings curated for this source.
PMID:9713119
[Prevalence study of biotinidase deficiency in newborns].
No top-level findings curated for this source.
PMID:33572391
Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening.
No top-level findings curated for this source.
PMID:36759144
Neuroimaging Features of Biotinidase Deficiency.
No top-level findings curated for this source.
PMID:37027963
Biotinidase deficiency: What have we learned in forty years?
No top-level findings curated for this source.
PMID:3736876
Biotinidase deficiency: accumulation of lactate in the brain and response to physiologic doses of biotin.
No top-level findings curated for this source.
PMID:37373384
Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking.
No top-level findings curated for this source.
PMID:38141137
Evaluation of clinical, laboratory, and molecular genetic features of patients with biotinidase deficiency.
No top-level findings curated for this source.
PMID:38928282
Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives.
No top-level findings curated for this source.
PMID:39451125
A retrospective study on biotinidase deficiency: analysis of the Eastern Anatolia region patient cohort.
No top-level findings curated for this source.
PMID:40190376
Biotinidase Deficiency Induced Optic Neuropathy: A Case Report and Literature Review.
No top-level findings curated for this source.
PMID:9350481
Multiple carboxylase deficiency: inherited and acquired disorders of biotin metabolism.
No top-level findings curated for this source.
PMID:9427142
Cerebral metabolic changes in biotinidase deficiency.
No top-level findings curated for this source.
PMID:21051254
Development and characterization of a mouse with profound biotinidase deficiency: a biotin-responsive neurocutaneous disorder.
No top-level findings curated for this source.
PMID:22579707
Neurological deficits in mice with profound biotinidase deficiency are associated with demylination and axonal degeneration.
No top-level findings curated for this source.
PMID:24075304
Biotinidase knockout mice show cellular energy deficit and altered carbon metabolism gene expression similar to that of nutritional biotin deprivation: clues for the pathogenesis in the human inherited disorder.
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Pathophysiology description (concise knowledge-base paragraph)
Edison Scientific Literature 24 citations 2026-02-23T23:22:35.665470

Pathophysiology description (concise knowledge-base paragraph) BTD deficiency is an autosomal recessive disorder caused by loss of biotinidase activity, leading to failure of biotin recycling from biocytin/biotinyl-peptides and subsequent depletion of free biotin. The resulting functional deficiency of biotin-dependent carboxylases (including pyruvate carboxylase, propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase) causes metabolic acidosis/lactic acidosis, hyperammonemia, and organic aciduria with characteristic elevations such as C3 and C5‑OH acylcarnitines and urinary 3-hydroxyisovalerate/methylcitrate. CNS-predominant injury includes white matter/myelination abnormalities and involvement of specific neuroanatomical structures (e.g., fornices/brainstem/optic pathways/spinal cord), producing seizures, developmental delay, hypotonia, and potentially irreversible hearing/vision loss when untreated or treated late. Early newborn screening and prompt, lifelong oral biotin prevent disease manifestation in most cases. (devanapalli2024biotinidasedeficiencya pages 1-3, karachaliou2024biotinhomeostasisand pages 5-7, devanapalli2024biotinidasedeficiencya pages 3-5, biswas2023neuroimagingfeaturesof pages 3-4)

Gene/protein annotations • BTD (biotinidase) — causal gene; biallelic pathogenic variants reduce enzyme activity; severity correlates with residual activity categories (profound vs partial). (devanapalli2024biotinidasedeficiencya pages 1-3, karachaliou2024biotinhomeostasisand pages 5-7)

Representative genotype–phenotype notes (recent cohort) • Turin NBS cohort: D444H associated mostly with partial BTD; Q456H present in many profound cases; complex allele A171T/D444H can yield partial or profound depending on trans allele. (bracci2024biotinidasedeficiencyoutcomes pages 10-12)

GO biological process candidates (mechanism-linked) • Biotin metabolic process / biotin recycling (biotin cycle). (karachaliou2024biotinhomeostasisand pages 4-5) • Protein biotinylation / activation of carboxylases (HLCS-mediated). (karachaliou2024biotinhomeostasisand pages 4-5) • Gluconeogenesis (PC-linked) and propionate metabolism (PCC-linked). (karachaliou2024biotinhomeostasisand pages 5-7)

Cellular component candidates • Cytosol and mitochondrion (intermediary metabolism/organic acidemia-like biochemical phenotype implicates mitochondrial/cytosolic metabolic pathways). (devanapalli2024biotinidasedeficiencya pages 1-3, karachaliou2024biotinhomeostasisand pages 5-7)

Phenotype associations (HP term examples; evidence-supported) • Seizures; hypotonia; developmental delay; ataxia; hearing loss; optic atrophy/vision loss; skin rash; alopecia; metabolic acidosis; hyperammonemia; organic aciduria. (devanapalli2024biotinidasedeficiencya pages 1-3, devanapalli2024biotinidasedeficiencya pages 3-5, motta2024organicacidemiasclinical pages 9-10, biswas2023neuroimagingfeaturesof pages 3-4)

Cell type involvement (CL examples) • Cerebellar Purkinje cells (localization evidence). (devanapalli2024biotinidasedeficiencya pages 3-5) • Auditory brainstem nuclei (localization evidence). (devanapalli2024biotinidasedeficiencya pages 3-5)

Anatomical locations (UBERON examples) • Brain white matter/cerebellum/red nucleus/brainstem/optic pathway/spinal cord; skin. (devanapalli2024biotinidasedeficiencya pages 3-5, biswas2023neuroimagingfeaturesof pages 3-4)

Chemical entities (CHEBI examples) • Biotin; biocytin; lactate; propionylcarnitine (C3); 3-hydroxyisovaleryl-carnitine (C5‑OH); 3-hydroxyisovaleric acid; methylcitrate. (devanapalli2024biotinidasedeficiencya pages 1-3, karachaliou2024biotinhomeostasisand pages 5-7, liu2023delayedbiotintherapy pages 2-3)

13) Evidence items (PMID preference; availability note)

The retrieved full-text snippets in this run did not include PMIDs inline for the core 2024 IJMS review or the 2024 Brain & Development Case Reports article; however, peer-reviewed sources with DOI/URL and publication dates are provided below and are suitable for citation.

Key recent sources (URLs and publication dates) • Karachaliou C‑E, Livaniou E. “Biotin Homeostasis and Human Disorders: Recent Findings and Perspectives.” International Journal of Molecular Sciences. June 2024. https://doi.org/10.3390/ijms25126578 (karachaliou2024biotinhomeostasisand pages 5-7) • Devanapalli B, et al. “Biotinidase deficiency: A treatable neurometabolic disorder.” Brain and Development Case Reports. June 2024. https://doi.org/10.1016/j.bdcasr.2024.100021 (devanapalli2024biotinidasedeficiencya pages 1-3, devanapalli2024biotinidasedeficiencya pages 3-5, devanapalli2024biotinidasedeficiencya pages 5-7) • Biswas A, et al. “Neuroimaging Features of Biotinidase Deficiency.” American Journal of Neuroradiology. February 2023. https://doi.org/10.3174/ajnr.a7781 (biswas2023neuroimagingfeaturesof pages 1-3, biswas2023neuroimagingfeaturesof pages 3-4) • Liu S, et al. “Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency…” International Journal of Molecular Sciences. June 2023. https://doi.org/10.3390/ijms241210239 (liu2023delayedbiotintherapy pages 1-2, liu2023delayedbiotintherapy pages 2-3)

Limitations This tool run retrieved strong mechanistic and real-world screening/treatment evidence but did not successfully obtain the full text of one highly relevant 2023 historical synthesis (“Biotinidase deficiency: what have we learned in forty years?”, doi:10.1016/j.ymgme.2023.107560) and therefore cannot directly quote/cite it here. (No citeable context available in this run.)

References

  1. (bracci2024biotinidasedeficiencyoutcomes pages 10-12): B Bracci, D Mala, E Pavanello, and P Sauro. Biotinidase deficiency: outcomes of 37 years-experience of newborn screening in turin, italy. Unknown journal, 2024.

  2. (devanapalli2024biotinidasedeficiencya pages 1-3): Beena Devanapalli, Rachel Sze Hui Wong, Natalie Lim, P Ian Andrews, Keshini Vijayan, Won-Tae Kim, Tiffany Wotton, Esther Tantsis, Enzo Ranieri, Adviye Ayper Tolun, and Shanti Balasubramaniam. Biotinidase deficiency: a treatable neurometabolic disorder. Brain and Development Case Reports, 2:100021, Jun 2024. URL: https://doi.org/10.1016/j.bdcasr.2024.100021, doi:10.1016/j.bdcasr.2024.100021. This article has 5 citations.

  3. (karachaliou2024biotinhomeostasisand pages 5-7): Chrysoula-Evangelia Karachaliou and Evangelia Livaniou. Biotin homeostasis and human disorders: recent findings and perspectives. International Journal of Molecular Sciences, 25:6578, Jun 2024. URL: https://doi.org/10.3390/ijms25126578, doi:10.3390/ijms25126578. This article has 45 citations.

  4. (motta2024organicacidemiasclinical pages 9-10): Mario Motta, Mohammad Mozibur Rahman, Gayatri Athalye-Jape, and Monika Kaushal. Organic acidemias: clinical presentation in neonates. Newborn, 2:263-278, Jan 2024. URL: https://doi.org/10.5005/jp-journals-11002-0080, doi:10.5005/jp-journals-11002-0080. This article has 3 citations.

  5. (karachaliou2024biotinhomeostasisand pages 4-5): Chrysoula-Evangelia Karachaliou and Evangelia Livaniou. Biotin homeostasis and human disorders: recent findings and perspectives. International Journal of Molecular Sciences, 25:6578, Jun 2024. URL: https://doi.org/10.3390/ijms25126578, doi:10.3390/ijms25126578. This article has 45 citations.

  6. (karachaliou2024biotinhomeostasisand media 2c556c74): Chrysoula-Evangelia Karachaliou and Evangelia Livaniou. Biotin homeostasis and human disorders: recent findings and perspectives. International Journal of Molecular Sciences, 25:6578, Jun 2024. URL: https://doi.org/10.3390/ijms25126578, doi:10.3390/ijms25126578. This article has 45 citations.

  7. (karachaliou2024biotinhomeostasisand media c7e991bf): Chrysoula-Evangelia Karachaliou and Evangelia Livaniou. Biotin homeostasis and human disorders: recent findings and perspectives. International Journal of Molecular Sciences, 25:6578, Jun 2024. URL: https://doi.org/10.3390/ijms25126578, doi:10.3390/ijms25126578. This article has 45 citations.

  8. (karachaliou2024biotinhomeostasisand media c9e70a46): Chrysoula-Evangelia Karachaliou and Evangelia Livaniou. Biotin homeostasis and human disorders: recent findings and perspectives. International Journal of Molecular Sciences, 25:6578, Jun 2024. URL: https://doi.org/10.3390/ijms25126578, doi:10.3390/ijms25126578. This article has 45 citations.

  9. (devanapalli2024biotinidasedeficiencya pages 3-5): Beena Devanapalli, Rachel Sze Hui Wong, Natalie Lim, P Ian Andrews, Keshini Vijayan, Won-Tae Kim, Tiffany Wotton, Esther Tantsis, Enzo Ranieri, Adviye Ayper Tolun, and Shanti Balasubramaniam. Biotinidase deficiency: a treatable neurometabolic disorder. Brain and Development Case Reports, 2:100021, Jun 2024. URL: https://doi.org/10.1016/j.bdcasr.2024.100021, doi:10.1016/j.bdcasr.2024.100021. This article has 5 citations.

  10. (biswas2023neuroimagingfeaturesof pages 1-3): A. Biswas, C. McNamara, V. Gowda, F. Gala, S. Sudhakar, M. S. J. Sidpra, P. Vari, S. Striano, M. Blaser, S. Severino, K. Batzios, Mankad, Istituto di Ricovero e Cura, and Carattere Scientifico. Neuroimaging features of biotinidase deficiency. American Journal of Neuroradiology, 44:328-333, Feb 2023. URL: https://doi.org/10.3174/ajnr.a7781, doi:10.3174/ajnr.a7781. This article has 17 citations and is from a peer-reviewed journal.

  11. (biswas2023neuroimagingfeaturesof pages 3-4): A. Biswas, C. McNamara, V. Gowda, F. Gala, S. Sudhakar, M. S. J. Sidpra, P. Vari, S. Striano, M. Blaser, S. Severino, K. Batzios, Mankad, Istituto di Ricovero e Cura, and Carattere Scientifico. Neuroimaging features of biotinidase deficiency. American Journal of Neuroradiology, 44:328-333, Feb 2023. URL: https://doi.org/10.3174/ajnr.a7781, doi:10.3174/ajnr.a7781. This article has 17 citations and is from a peer-reviewed journal.

  12. (alharbi2023overviewonpathophysiology pages 2-4): Faisal Mohammed Alharbi, Ahmad Sughaier Albalawi, Fawaz Khalifah Alanazi, Turki Saleh Alshehri, Badriah Abdulrahman Alsabah, and Alaa Saud Alyasi. Overview on pathophysiology, diagnosis, and management of biotinidase deficiency in pediatrics. Archives of Pharmacy Practice, 14:99-105, Jan 2023. URL: https://doi.org/10.51847/8hpvomjrdl, doi:10.51847/8hpvomjrdl. This article has 1 citations.

  13. (liu2023delayedbiotintherapy pages 6-7): Shu Liu, Ye Zhang, Zhi Deng, Hui He, Xianhua Zheng, Qingshan Hong, and Xianqiong Luo. Delayed biotin therapy in a child with atypical profound biotinidase deficiency: late arrival of the truth and a lesson worth thinking. International Journal of Molecular Sciences, 24:10239, Jun 2023. URL: https://doi.org/10.3390/ijms241210239, doi:10.3390/ijms241210239. This article has 4 citations.

  14. (liu2023delayedbiotintherapy pages 1-2): Shu Liu, Ye Zhang, Zhi Deng, Hui He, Xianhua Zheng, Qingshan Hong, and Xianqiong Luo. Delayed biotin therapy in a child with atypical profound biotinidase deficiency: late arrival of the truth and a lesson worth thinking. International Journal of Molecular Sciences, 24:10239, Jun 2023. URL: https://doi.org/10.3390/ijms241210239, doi:10.3390/ijms241210239. This article has 4 citations.

  15. (liu2023delayedbiotintherapy pages 2-3): Shu Liu, Ye Zhang, Zhi Deng, Hui He, Xianhua Zheng, Qingshan Hong, and Xianqiong Luo. Delayed biotin therapy in a child with atypical profound biotinidase deficiency: late arrival of the truth and a lesson worth thinking. International Journal of Molecular Sciences, 24:10239, Jun 2023. URL: https://doi.org/10.3390/ijms241210239, doi:10.3390/ijms241210239. This article has 4 citations.

  16. (liu2023delayedbiotintherapy pages 3-6): Shu Liu, Ye Zhang, Zhi Deng, Hui He, Xianhua Zheng, Qingshan Hong, and Xianqiong Luo. Delayed biotin therapy in a child with atypical profound biotinidase deficiency: late arrival of the truth and a lesson worth thinking. International Journal of Molecular Sciences, 24:10239, Jun 2023. URL: https://doi.org/10.3390/ijms241210239, doi:10.3390/ijms241210239. This article has 4 citations.

  17. (devanapalli2024biotinidasedeficiencya pages 5-7): Beena Devanapalli, Rachel Sze Hui Wong, Natalie Lim, P Ian Andrews, Keshini Vijayan, Won-Tae Kim, Tiffany Wotton, Esther Tantsis, Enzo Ranieri, Adviye Ayper Tolun, and Shanti Balasubramaniam. Biotinidase deficiency: a treatable neurometabolic disorder. Brain and Development Case Reports, 2:100021, Jun 2024. URL: https://doi.org/10.1016/j.bdcasr.2024.100021, doi:10.1016/j.bdcasr.2024.100021. This article has 5 citations.