Biotinidase Deficiency

Mendelian MONDO:0009665 Pathograph 40 Metabolic Disease Inborn Error of Metabolism

Biotinidase deficiency is an autosomal recessive disorder of biotin recycling caused by biallelic pathogenic variants in the BTD gene. Deficient biotinidase activity impairs cleavage of biocytin and biotinyl-peptides, leading to depletion of free biotin and secondary functional deficiency of biotin-dependent carboxylases (pyruvate carboxylase, propionyl-CoA carboxylase, 3-methylcrotonyl- CoA carboxylase, and acetyl-CoA carboxylase). This results in metabolic acidosis, organic aciduria, and multisystem injury predominantly affecting the nervous system, skin, eyes, and auditory system. Profound deficiency (<10% residual activity) and partial deficiency (10-30%) are distinguished biochemically. Lifelong oral biotin supplementation is highly effective and prevents symptoms when initiated early through newborn screening. Delayed diagnosis can lead to irreversible neurological damage, hearing loss, and optic atrophy.

Ask OpenScientist

Ask a research question about Biotinidase Deficiency. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

4
Pathophys.
25
Phenotypes
40
Pathograph
2
Genes
6
Treatments
1
Deep Research
⚙

Pathophysiology

4
Impaired biotin recycling and secondary multiple carboxylase deficiency
Loss of biotinidase activity prevents efficient recycling of biotin from biocytin and biotinyl-peptides. This leads to depletion of free biotin and impaired biotinylation of apocarboxylases by holocarboxylase synthetase, resulting in functional deficiency of all four biotin-dependent carboxylases.
hepatocyte link
BTD link
biotin metabolic process link
biotinidase activity link ↓ DECREASED
mitochondrion link
Downstream
Disrupted intermediary metabolism and organic aciduria Loss of biotin recycling functionally impairs biotin-dependent carboxylases, producing toxic metabolite accumulation.
Decreased biotinidase activity BTD pathogenic variation is reflected clinically by reduced serum biotinidase activity.
Show evidence (2 references)
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.
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"
Confirms that biotinidase deficiency leads to impaired carboxylase activity and toxic metabolite accumulation.
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 link
gluconeogenesis link propionate catabolic process link leucine catabolic process link
pyruvate carboxylase activity link ↓ DECREASED propionyl-CoA carboxylase activity link ↓ DECREASED methylcrotonoyl-CoA carboxylase activity link ↓ DECREASED acetyl-CoA carboxylase activity link ↓ 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: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.
Central nervous system vulnerability and white matter injury
The CNS is particularly vulnerable in biotinidase deficiency. Neuropathologic changes include defective myelination, spongy white-matter changes, and involvement of specific neuroanatomical structures including fornices, brainstem, optic pathways, and spinal cord. Biotinidase localization to cerebellar Purkinje cells and auditory brainstem nuclei is consistent with frequent neurologic and auditory phenotypes.
Purkinje cell link oligodendrocyte link
myelination link
brain white matter link cerebellum link
Downstream
Brain imaging abnormality White-matter, cerebellar, optic-pathway, and brainstem involvement 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 Cerebellar involvement can manifest with ataxia.
Intellectual disability Delayed treatment can leave persistent cognitive deficits after CNS injury.
Spastic paraparesis Spinal cord and white-matter involvement can manifest with spastic paraparesis.
Sensorineural hearing impairment Auditory pathway vulnerability can produce sensorineural hearing impairment.
Optic atrophy Optic pathway involvement can manifest as optic atrophy.
Show evidence (2 references)
PMID:36759144 SUPPORT Human Clinical
"Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms"
Multicenter neuroimaging study documenting CNS involvement patterns in biotinidase deficiency.
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.
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 link
fatty acid biosynthetic process link
skin of body link
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.
●

Phenotypes

25
Cardiovascular 1
Conjunctivitis OCCASIONAL Conjunctivitis (HP:0000509)
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
"HP:0000509 | Conjunctivitis | Occasional (29-5%)"
Orphanet classifies conjunctivitis as occasional in biotinidase deficiency.
Ear 1
Sensorineural hearing impairment FREQUENT Sensorineural hearing impairment (HP:0000407)
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
"HP:0000407 | Sensorineural hearing impairment | Frequent (79-30%)"
Orphanet classifies sensorineural hearing impairment as frequent in biotinidase deficiency.
Eye 1
Optic atrophy OCCASIONAL Optic atrophy (HP:0000648)
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
"HP:0000648 | Optic atrophy | Occasional (29-5%)"
Orphanet classifies optic atrophy as occasional in biotinidase deficiency.
Genitourinary 1
Organic aciduria VERY_FREQUENT Organic aciduria (HP:0001992)
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
"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 Skin rash (HP:0000988)
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 Eczematoid dermatitis (HP:0000964)
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
"HP:0000964 | Eczematoid dermatitis | Occasional (29-5%)"
Orphanet classifies eczematoid dermatitis as occasional in biotinidase deficiency.
Integument 1
Alopecia OCCASIONAL Alopecia (HP:0001596)
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
"HP:0001596 | Alopecia | Occasional (29-5%)"
Orphanet classifies alopecia as occasional in biotinidase deficiency.
Metabolism 2
Metabolic acidosis FREQUENT Metabolic acidosis (HP:0001942)
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 Hyperammonemia (HP:0001987)
Show evidence (1 reference)
ORPHA:79241 SUPPORT
"HP:0001987 | Hyperammonemia | Frequent (79-30%)"
Orphanet classifies hyperammonemia as frequent in biotinidase deficiency.
Musculoskeletal 2
Muscular hypotonia FREQUENT Hypotonia (HP:0001252)
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 Spastic paraparesis (HP:0002313)
Show evidence (2 references)
PMID:36759144 PARTIAL Human Clinical
"In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups"
Neuroimaging series supports neurologic involvement but does not directly name spastic paraparesis.
ORPHA:79241 SUPPORT
"HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
Orphanet classifies spastic paraparesis as occasional in biotinidase deficiency.
Nervous System 5
Seizures FREQUENT Seizure (HP:0001250)
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 Global developmental delay (HP:0001263)
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
"HP:0001263 | Global developmental delay | Occasional (29-5%)"
Orphanet classifies global developmental delay as occasional in biotinidase deficiency.
Ataxia OCCASIONAL Ataxia (HP:0001251)
Show evidence (1 reference)
PMID:36759144 PARTIAL Human Clinical
"Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms"
Neuroimaging study documents cerebellar and brainstem involvement consistent with ataxia.
Intellectual disability OCCASIONAL Intellectual disability (HP:0001249)
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.
Lethargy OCCASIONAL Lethargy (HP:0001254)
Show evidence (1 reference)
ORPHA:79241 SUPPORT
"HP:0001254 | Lethargy | Occasional (29-5%)"
Orphanet classifies lethargy as occasional in biotinidase deficiency.
Respiratory 2
Respiratory distress OCCASIONAL Respiratory distress (HP:0002098)
Show evidence (2 references)
ORPHA:79241 SUPPORT
"HP:0002098 | Respiratory distress | Occasional (29-5%)"
Orphanet classifies respiratory distress as occasional in biotinidase deficiency.
PMID:37027963 PARTIAL 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 Apnea (HP:0002104)
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
"HP:0002104 | Apnea | Occasional (29-5%)"
Orphanet classifies apnea as occasional in biotinidase deficiency.
Growth 1
Failure to thrive OCCASIONAL Failure to thrive (HP:0001508)
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 6
Metabolic ketoacidosis VERY_FREQUENT Metabolic ketoacidosis (HP:0005979)
Show evidence (2 references)
PMID:37027963 PARTIAL 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
"HP:0005979 | Metabolic ketoacidosis | Very frequent (99-80%)"
Orphanet classifies metabolic ketoacidosis as very frequent in biotinidase deficiency.
Laryngeal stridor OCCASIONAL Laryngeal stridor (HP:0006511)
Show evidence (1 reference)
ORPHA:79241 SUPPORT
"HP:0006511 | Laryngeal stridor | Occasional (29-5%)"
Orphanet classifies laryngeal stridor as occasional in biotinidase deficiency.
Recurrent fungal infections OCCASIONAL Recurrent fungal infections (HP:0002841)
Show evidence (1 reference)
ORPHA:79241 SUPPORT
"HP:0002841 | Recurrent fungal infections | Occasional (29-5%)"
Orphanet classifies recurrent fungal infections as occasional in biotinidase deficiency.
Brain imaging abnormality FREQUENT Brain imaging abnormality (HP:0410263)
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
"HP:0410263 | Brain imaging abnormality | Frequent (79-30%)"
Orphanet classifies brain imaging abnormality as frequent in biotinidase deficiency.
Infantile spasms OCCASIONAL Infantile spasms (HP:0012469)
Show evidence (1 reference)
ORPHA:79241 SUPPORT
"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)
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
"HP:0410145 | Decreased biotinidase activity | Very frequent (99-80%)"
Orphanet classifies decreased biotinidase activity as very frequent (diagnostic hallmark).
🧬

Genetic Associations

2
BTD gene variants causing biotinidase deficiency
Autosomal recessive
Show evidence (3 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
"BTD | biotinidase | hgnc:1122 | Disease-causing germline mutation(s) in"
Orphanet confirms BTD as the disease-causing gene for biotinidase deficiency.
BTD (Pathogenic Variants)
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"
ClinGen classifies the BTD-biotinidase deficiency gene-disease relationship as definitive with autosomal recessive inheritance.
💊

Treatments

6
Oral biotin supplementation
Action: nutritional supplementation MAXO:0000106
Agent: biotin ↗
Lifelong oral free biotin is the definitive disease-modifying therapy for biotinidase deficiency. Recommended doses are 5-20 mg daily for profound deficiency and 2.5-10 mg for partial deficiency. Biotin treatment led to clinical stability or improvement in 89.2% of individuals in a systematic review. Early treatment can prevent all symptoms.
Mechanism Target:
BYPASSES Impaired biotin recycling and secondary multiple carboxylase deficiency — 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.
Show evidence (2 references)
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.
PMID:40190376 SUPPORT Human Clinical
"The patient was treated with oral biotin supplementation with improvement in her visual function"
Case demonstrating biotin supplementation improving visual function in an adult patient.
Newborn screening
Action: disease screening MAXO:0000124
Biotinidase deficiency is widely included in newborn screening programs using biotinidase activity assays on dried blood spots. Newborn screening has had a major positive impact on outcomes. No deaths occurred among those detected by newborn screening and treated pre-symptomatically.
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"
Systematic review confirms the positive impact of newborn screening on outcomes.
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"
Large cohort demonstrating that newborn screening identifies the vast majority of cases.
Antiseizure medication
Action: antiepileptic drug therapy Ontology label: anticonvulsant agent therapy MAXO:0000167
Anticonvulsant therapy may be needed for seizure management, although seizures often resolve with biotin supplementation alone. Antiepileptic therapy alone without biotin is typically insufficient.
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 counseling MAXO:0000079
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 (2 references)
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
Action: supportive care MAXO:0000950
Acute and chronic supportive management to reduce metabolic instability and complications. Includes monitoring of neurological, auditory, and visual function, and management of metabolic decompensation during intercurrent illness.
Show evidence (1 reference)
PMID:37027963 SUPPORT Human Clinical
"a trial of biotin should be considered in undiagnosed infants and adults exhibiting suspected clinical signs. Enzymatic activity and/or analysis of genetic variants can readily confirm the diagnosis of BD"
Supports comprehensive monitoring and supportive care approach for affected individuals.
Audiological management
Action: supportive care MAXO:0000950
Regular audiological assessment and hearing aid or cochlear implant consideration for patients with sensorineural hearing loss, which may be irreversible once established.
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%)"
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.
🔬

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 PARTIAL 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 PARTIAL 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 PARTIAL 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 and secondary multiple carboxylase deficiency 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.
{ }

Source YAML

click to show 
name: Biotinidase Deficiency
category: Mendelian
creation_date: '2025-06-12T20:16:27Z'
updated_date: '2026-05-21T03:52:18Z'
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 the BTD gene. Deficient biotinidase activity impairs cleavage of biocytin and biotinyl-peptides, leading to depletion of free biotin and secondary functional deficiency of biotin-dependent carboxylases (pyruvate carboxylase, propionyl-CoA carboxylase, 3-methylcrotonyl- CoA carboxylase, and acetyl-CoA carboxylase). This results in metabolic acidosis, organic aciduria, and multisystem injury predominantly affecting the nervous system, skin, eyes, and auditory system. Profound deficiency (<10% residual activity) and partial deficiency (10-30%) are distinguished biochemically. Lifelong oral biotin supplementation is highly effective and prevents symptoms when initiated early through newborn screening. Delayed diagnosis can lead to irreversible neurological damage, hearing loss, and optic atrophy.

  '
disease_term:
  preferred_term: biotinidase deficiency
  term:
    id: MONDO:0009665
    label: biotinidase deficiency
parents:
- Metabolic Disease
- Inborn Error of Metabolism
prevalence:
- population: Newborn screening cohorts
  percentage: 1 in 61,067
  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
    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
    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
    supports: SUPPORT
    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.
pathophysiology:
- name: Impaired biotin recycling and secondary multiple carboxylase deficiency
  description: 'Loss of biotinidase activity prevents efficient recycling of biotin from biocytin and biotinyl-peptides. This leads to depletion of free biotin and impaired biotinylation of apocarboxylases by holocarboxylase synthetase, resulting in functional deficiency of all four biotin-dependent carboxylases.

    '
  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
  cellular_components:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  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.
  - 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: Confirms that biotinidase deficiency leads to impaired carboxylase activity and toxic metabolite accumulation.
  downstream:
  - target: Disrupted intermediary metabolism and organic aciduria
    description: Loss of biotin recycling functionally impairs biotin-dependent carboxylases, producing 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 BTD deficiency to multiple carboxylase dysfunction and metabolite accumulation.
  - 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: 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).

    '
  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: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: 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: PARTIAL
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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: 'The CNS is particularly vulnerable in biotinidase deficiency. Neuropathologic changes include defective myelination, spongy white-matter changes, and involvement of specific neuroanatomical structures including fornices, brainstem, optic pathways, and spinal cord. Biotinidase localization to cerebellar Purkinje cells and auditory brainstem nuclei is consistent with frequent neurologic and auditory phenotypes.

    '
  biological_processes:
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  - 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: Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms
    explanation: Multicenter neuroimaging study documenting CNS involvement patterns in biotinidase deficiency.
  - 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.
  downstream:
  - target: Brain imaging abnormality
    description: White-matter, cerebellar, optic-pathway, and brainstem involvement 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
      supports: SUPPORT
      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
      supports: SUPPORT
      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: Cerebellar involvement can manifest with ataxia.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Cerebellar hypoplasia and Purkinje-cell-region vulnerability disrupt motor coordination.
    evidence:
    - reference: PMID:36759144
      reference_title: "Neuroimaging Features of Biotinidase Deficiency."
      supports: PARTIAL
      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: The imaging study supports neurologic symptoms from carboxylase impairment; the edge uses the curated cerebellar vulnerability context.
  - 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: Spinal cord and white-matter involvement can manifest with spastic paraparesis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: ORPHA:79241
      supports: SUPPORT
      snippet: "HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
      explanation: Orphanet supports spastic paraparesis as an occasional neurologic manifestation.
  - target: Sensorineural hearing impairment
    description: Auditory pathway vulnerability can produce sensorineural hearing impairment.
    causal_link_type: INDIRECT_KNOWN_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: Optic pathway involvement can manifest as optic atrophy.
    causal_link_type: INDIRECT_KNOWN_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.
- 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.

    '
  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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
      supports: SUPPORT
      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
    supports: SUPPORT
    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
    supports: SUPPORT
    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 and is attributed to auditory brainstem involvement. 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
    supports: SUPPORT
    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
    supports: SUPPORT
    snippet: "HP:0000648 | Optic atrophy | Occasional (29-5%)"
    explanation: Orphanet classifies optic atrophy as occasional in biotinidase deficiency.
- name: Ataxia
  frequency: OCCASIONAL
  description: 'Cerebellar ataxia can occur in biotinidase deficiency, consistent with cerebellar involvement demonstrated on neuroimaging.

    '
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:36759144
    reference_title: "Neuroimaging Features of Biotinidase Deficiency."
    supports: PARTIAL
    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 study documents cerebellar and brainstem involvement consistent with ataxia.
- 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
    supports: SUPPORT
    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: PARTIAL
    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: 'Myelopathy with spastic paraparesis has been reported in severe or late-diagnosed cases, consistent with spinal cord involvement on neuroimaging.

    '
  phenotype_term:
    preferred_term: Spastic paraparesis
    term:
      id: HP:0002313
      label: Spastic paraparesis
  evidence:
  - reference: PMID:36759144
    reference_title: "Neuroimaging Features of Biotinidase Deficiency."
    supports: PARTIAL
    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: Neuroimaging series supports neurologic involvement but does not directly name spastic paraparesis.
  - reference: ORPHA:79241
    supports: SUPPORT
    snippet: "HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
    explanation: Orphanet classifies spastic paraparesis as occasional in biotinidase deficiency.
- 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
    supports: SUPPORT
    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
    supports: SUPPORT
    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: PARTIAL
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    snippet: "HP:0000509 | Conjunctivitis | Occasional (29-5%)"
    explanation: Orphanet classifies conjunctivitis as occasional in biotinidase deficiency.
- name: Brain imaging abnormality
  frequency: FREQUENT
  description: 'MRI abnormalities including white matter changes, cerebellar atrophy, and involvement of optic pathways and brainstem are characteristic neuroimaging findings 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
    supports: SUPPORT
    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
    supports: SUPPORT
    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
    supports: SUPPORT
    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: PARTIAL
      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: PARTIAL
    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: PARTIAL
    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 and secondary multiple carboxylase deficiency
    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
  inheritance:
  - name: Autosomal recessive
    evidence:
    - 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 that was first described in 1982
      explanation: Definitive statement of autosomal recessive inheritance in the landmark systematic review.
    - 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: Biotinidase (BTD) deficiency (OMIM 253260) is an autosomal recessively inherited metabolic disorder
      explanation: Case report confirms autosomal recessive inheritance pattern.
    - reference: ORPHA:79241
      supports: SUPPORT
      snippet: "Autosomal recessive"
      explanation: Orphanet confirms autosomal recessive inheritance for biotinidase deficiency.
  variants:
  - name: c.1270G>C (p.Asp424His)
    description: 'The most common BTD variant worldwide. Associated predominantly with partial biotinidase deficiency when homozygous. This variant is often also written as p.Asp444His when full-length protein numbering is used. Biotinidase enzyme activity is above 30% in 97.3% of patients with homozygous p.Asp424His.

      '
    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: Identifies D424H as the most frequent variant with characterization of enzyme activity levels.
    - 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: 'Associated with profound enzyme deficiency. More commonly observed in patients with neurological symptoms.

      '
    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: 'Frameshift variant associated with profound enzyme deficiency and severe phenotype including hearing loss and optic atrophy.

      '
    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 variants in BTD (chromosome 3p25.1) reduce biotinidase enzyme activity. Over 294 pathogenic variants have been identified. Severity correlates with residual enzyme activity: profound deficiency (<10% activity) and partial deficiency (10-30% activity). Genotype-phenotype correlations show that specific variants predict severity, with c.1270G>C associated with milder partial deficiency and c.410G>A and frameshift variants associated with profound deficiency and neurological complications.

    '
  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
    supports: SUPPORT
    snippet: "BTD | biotinidase | hgnc:1122 | Disease-causing germline mutation(s) in"
    explanation: Orphanet confirms BTD as the disease-causing gene for biotinidase deficiency.
- name: BTD
  gene_term:
    preferred_term: BTD
    term:
      id: hgnc:1122
      label: BTD
  association: Pathogenic Variants
  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: ClinGen classifies the BTD-biotinidase deficiency gene-disease relationship as definitive with autosomal recessive inheritance.
treatments:
- name: Oral biotin supplementation
  description: 'Lifelong oral free biotin is the definitive disease-modifying therapy for biotinidase deficiency. Recommended doses are 5-20 mg daily for profound deficiency and 2.5-10 mg for partial deficiency. Biotin treatment led to clinical stability or improvement in 89.2% of individuals in a systematic review. Early treatment can prevent all symptoms.

    '
  treatment_term:
    preferred_term: nutritional supplementation
    term:
      id: MAXO:0000106
      label: nutritional supplementation
    therapeutic_agent:
    - preferred_term: biotin
      term:
        id: CHEBI:15956
        label: biotin
  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. 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 and secondary multiple carboxylase deficiency
    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.
- name: Newborn screening
  description: 'Biotinidase deficiency is widely included in newborn screening programs using biotinidase activity assays on dried blood spots. Newborn screening has had a major positive impact on outcomes. No deaths occurred among those detected by newborn screening and treated pre-symptomatically.

    '
  treatment_term:
    preferred_term: disease screening
    term:
      id: MAXO:0000124
      label: disease screening
  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: Systematic review confirms the positive impact of newborn screening on outcomes.
  - 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: Large cohort demonstrating that newborn screening identifies the vast majority of cases.
- 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.

    '
  treatment_term:
    preferred_term: antiepileptic drug therapy
    term:
      id: MAXO:0000167
      label: anticonvulsant agent therapy
  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: MAXO:0000079
      label: genetic counseling
  evidence:
  - 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: 'Acute and chronic supportive management to reduce metabolic instability and complications. Includes monitoring of neurological, auditory, and visual function, and management of metabolic decompensation during intercurrent illness.

    '
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:37027963
    reference_title: "Biotinidase deficiency: What have we learned in forty years?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a trial of biotin should be considered in undiagnosed infants and adults exhibiting suspected clinical signs. Enzymatic activity and/or analysis of genetic variants can readily confirm the diagnosis of BD
    explanation: Supports comprehensive monitoring and supportive care approach for affected individuals.
- 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.

    '
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  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: 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.
notes: 'Biotinidase deficiency is one of the most treatable inborn errors of metabolism. The key clinical message is that early diagnosis through newborn screening and prompt lifelong biotin supplementation prevent virtually all clinical manifestations. Delayed diagnosis carries risk of irreversible neurological damage, hearing loss, and optic atrophy. The disorder has two severity classes based on residual enzyme activity: profound (<10%) and partial (10-30%). A systematic review of 1113 cases found that no deaths occurred among individuals detected by newborn screening and treated pre-symptomatically. Genotype-phenotype correlations show c.1270G>C (p.Asp424His) is associated with partial deficiency while c.410G>A (p.Arg137His) and frameshift variants are associated with profound deficiency and more severe clinical outcomes.

  Prevalence: Global incidence is commonly cited as approximately 1:40,000-1:60,000. Significant regional variation exists, with higher rates in populations with elevated consanguinity. Turkey reports national incidence of approximately 1:7,116 and as high as 1:2,359 in some regions.

  Progression: Without treatment, biotinidase deficiency progresses from subclinical biotin depletion to functional multiple carboxylase deficiency, then metabolic decompensation with organic aciduria and lactic acidosis, and finally tissue injury with irreversible neurological, auditory, and visual sequelae. Earlier diagnosis and treatment improve reversibility, with prompt biotin able to reverse seizures and motor signs. Neurological deficits become permanent once established.'
📚

References & Deep Research

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.