Adult-onset biotinidase deficiency: two individuals with severe, but reversible optic neuropathy

Introduction

Biotinidase is an enzyme that recycles biotin, a water-soluble vitamin essential as the coenzyme for four carboxylases that are involved in gluconeogenesis, fatty acid synthesis and in the catabolism of several branched-chain amino acids. Biotinidase deficiency (BD) is an autosomal recessively inherited disorder. Individuals with profound BD (<10% of mean normal serum biotinidase activity) present usually during early childhood with neurological disorders (seizures, hypotonia, ataxia, developmental delay, vision problems and hearing loss) and/or non-neurological findings (metabolic acidosis, respiratory difficulties, alopaecia and/or skin rash), that may progress to coma or death if untreated.1 Here, we present two cases of adult-onset BD with reversible optic neuropathy (ON).

Case reportsPatient 1

An 18-year-old man was referred with a 7-month history of bilateral progressive painless visual loss. He was born in France and his parents were from sub-Saharan Africa. There was no relevant familial medical history and no known consanguinity. On admission,...

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