[MIM*230200] an inborn error of metabolism due to congenital deficiency of galactokinase (GALK), resulting in increased blood galactose concentration (galactosemia), cataracts, hepatomegaly, and mental deficiency; autosomal recessive inheritance, caused by mutation in the GALK gene on 17q. Galactose epimerase deficiency [MIM*230350] and galactose-1-phosphate uridyl transferase deficiency [MIM*230400] produce much the same clinical picture.