RESUMO
Biotinidase deficiency is characterized by neurological and cutaneous manifestations that can be prevented or ameliorated by oral biotin therapy. The present work aims to establish the prevalence of biotinidase deficiency in a targeted group of infants and children presenting with neurological and cutaneous problems or isolated cutaneous symptoms, during a two year period. We measured biotinidase activity and obtained medical histories and examinations of probands, as well as of available parents and siblings. Among 13 children presenting with neurological symptoms associated with intractable seborrheic dermatitis and/or alopecia, we identified 6 patients with profound biotinidase deficiency [activity<10% of mean normal activity] and one patient with partial biotinidase deficiency [activity between l0%-30% of mean normal activity]. Among 40 infants presenting with isolated intractable seborrheic dermatitis, we identified one infant with profound biotinidase deficiency and another with partial biotinidase deficiency. Normal healthy controls had biotinidase activities within normal ranges, Biotinidase activity in 5 parents and 3 siblings was intermediate between those of probands and those of normal individuals. We identified one asymptomatic sibling with biotinidase activity in the partial activity range. Among the most common neurological findings on presentation were developmental delay or regression in 66.6%, hypotonia in 66.6%, seizures in 55.5%, neurosensory hearing loss in 33.3%, ataxia in 22.2% and optic atrophy in 22.2% of patients. One patient presented with a spontaneous episode of metabolic acidosis. Age of onset was between 1 and 3 months of age in 66.6% of patients. Two patients presented later than the usual age of onset. There was no clear relationship between age of onset and either severity or type of deficiency. All patients showed resolution of skin problems and marked improvement in neurological symptoms on oral biotin treatment. Detection of 9 cases of biotinidase deficiency during a two year period at a single metabolic unit indicates that biotinidase deficiency is not rare in Egypt. We suggest that biotinidase deficiency be considered in all children with neurological symptoms particularly those associated with cutaneous manifestations. Biotinidase deficiency should be considered in the differential diagnosis of intractable seborrheic dermatitis. The high incidence of biotinidase deficiency, the low cost of screening test, and the inexpensive therapy cost increase the importance of neonatal screening for biotinidase deficiency in Egypt. This would prevent permanent neurological damage or death in future children with biotinidase deficiency