Abstract
Biotinidase deficiency is an autosomal recessive disorder in which affected individuals are unable to recycle biotin. Untreated, children usually exhibit hypotonia, seizures, ataxia, developmental delay, and/or hearing loss. Individuals diagnosed by newborn screening have an excellent prognosis with life-long biotin supplementation. We report a young adult diagnosed with profound biotinidase deficiency by newborn screening who was asymptomatic while on therapy. At 18 years of age, 6 months after voluntarily discontinuation of biotin, he developed a progressive distal muscle weakness. Molecular analysis of the BTD gene showed a pathogenic homozygous duplication c.1372_1373dupT p.(Cys458LeufsTer26) (1). Despite 16 months since reintroduction of biotin, muscle strength only partially recovered. Transition to adulthood in chronic metabolic diseases is known to be associated with an increased risk for non-compliance. Neurological findings in this adult are similar to those described in others with adult-onset biotinidase deficiency. Long-term prognosis in non-compliant symptomatic adult with biotinidase deficiency likely depends on the delay and/or severity of intervening symptoms until reintroduction of biotin.
Highlights
Biotin is the coenzyme for multiple carboxylases involved in the catabolism of branched-chain amino acids, the synthesis of fatty acid and gluconeogenesis [2]
We report a young adult diagnosed with Biotinidase deficiency (BD) by newborn screening who voluntarily discontinued biotin supplementation at 18 years old and at 6 months later exhibited severe muscle weakness
Our individual with profound biotinidase deficiency was identified to have the disorder by newborn screening
Summary
Biotin is the coenzyme for multiple carboxylases involved in the catabolism of branched-chain amino acids, the synthesis of fatty acid and gluconeogenesis [2]. At the age of 18 years, he completely stopped taking biotin supplementation and at about 6 months later, he developed a progressive distal muscle weakness with bilateral foot drop for which he was hospitalized. Non-compliance over a period of more than 6 months prior to onset of neurological symptoms was confessed when the individual was confronted about taking his biotin, this was confirmed by a serum biotin concentration below 0.1 nmol/L (normal range: 0.3–3.8 nmol/L) in a stored serum sample collected 1 year earlier. Studies performed while he was taking 10 mg/d of biotin showed normal plasma lactate (1.37 mmol/L; normal range: 0.63 and 2.44 mmol/L) and ammonia concentrations (29 μmol/L; normal range: < 50 μmol/L).
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