Conditions such as 3-hydroxy-3-methylglutaryl-coenzyme A lyasedeficiency, β-ketothiolase deficiency, multiple carboxylase deficiency resultingfrom holocarboxylase synthetase or biotinidase deficiency, 2-methyl 3-hydroxybutyricacidemia, and 3-methylglutaconic aciduria may occur with elevation of C5OHacylcarnitine in asymptomatic infants. The gene discussed is HLCS; the disease is multiple carboxylase deficiency.