Two forms of biotin-responsive multiple carboxylase deficiency.

Biotin-responsive multiple carboxylase deficiencies are classified into early and late forms. The early form showed higher urinary excretion of 3-hydroxyisovalerate and 3-hydroxypropionate than the late form and was associated with normal plasma biotin concentrations. It is proposed that holocarboxylase synthetase and intestinal biotin absorption are defective in the early and late forms respectively.