Biotinidase Deficiency
Test
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Colorimetric assay for biotinidase; radioassay also available.
Genetics
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Autosomal recessive
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1/72,000 to 1/126,000 in US
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Mostly in whites
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Highest incidence world-wide in French Canadians
Pathology
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Biotinidase is a hydrolase that specifically cleaves biotin from biocytin
and biotinyl peptides. It is the primary defect in most individuals
with late-onset multiple carboxylase deficiency.
Diagnosis
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Symptoms have first presented at 2 weeks and up to 12 years. Mean
age of onset is 5 to 6 months
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With severe biotinidase deficiency, approximately 80-85% of patients have
metabolic ketoacidosis and organic acidemia. Death may occur.
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Severe deficiency shows both neurologic and cutaneous findings, including
myoclonic seizures, hypotonia, seborrheic or atopic dermatitis, partial
or complete alopecia and conjunctivitis
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Other common features include ataxia, hearing loss, optic atrophy and developmental
abnormalities
Treatment
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Oral biotin, which reverses the cutaneous and some of the neurologic findings.
Hearing loss and optic atrophy usually do not resolve. Risks of treatment
are unknown as oldest patient was only about 20 years of age (as of 1998).
Acknowledgment
This page is based on a 1998 presentation by Owen Rennert, Georgetown University
Medical Center, Department of Pediatrics, Division of Genetics.
Also see other Inborn Errors of Metabolism.
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Last modification: January 10, 2000