multiple carboxylase deficiency, an autosomal-recessive inherited aminoacidopathy correctable by biotin therapy and caused by deficiency of either of two enzymes necessary for activity of several biotin-containing carboxylases. It is characterized by metabolic ketoacidosis, excretion of organic acids in the urine, hyperammonemia, and variable manifestation of breathing difficulties, hypotonia, seizures, ataxia, alopecia, skin rash, and developmental delay. The neonatal form, caused by deficiency of holocaroxylase synthetase, may progress rapidly to coma; the juvenile form, caused by deficiency of biotinase, is characterized additionally by sensorineural deafness and optic atrophy.
