PROFOUND BIOTINIDASE DEFICIENCY IN 2 ASYMPTOMATIC ADULTS

Biotinidase deficiency is an autosomal-recessive disorder of biotin re cycling. Children with profound biotinidase deficiency usually have ne urological and cutaneous symptoms in early childhood, but they may not develop symptoms until adolescence. We now report on a man and a woma n with profound biotinidase deficiency who are asymptomatic and who we re diagnosed only because their biotinidase-deficient children were id entified by newborn screening, These adults have never exhibited sympt oms of the disorder and are homozygous for two different mutations res ulting in different aberrant enzymes. There is no evidence of an incre ased dietary intake of biotin to explain why they have remained asympt omatic. Although these adults may still be at risk for developing symp toms, they could represent a small group of individuals with profound biotinidase deficiency who will never develop clinical problems. Their lack of symptoms suggests that there are probably epigenetic factors that protect some enzyme-deficient individuals from developing symptom s, These individuals broaden the spectrum of expression of biotinidase deficiency. (C) 1997 Wiley-Liss, Inc.