Inclusion:  Male Female non-pregnant Female non-lactating subjects aged ≥2 to <18 years. Diagnosis of Classic Galactosemia, confirmed by decreased GALT (galactose-1-phosphate uridyltransferase gut-associated lymphoid tissue )activity in erythrocytes, or a historical record of diagnosis of GALT (galactose-1-phosphate uridyltransferase gut-associated lymphoid tissue ) deficiency.  Exclusion:  Male/Female with no significant health problems (other than classic Galactosemia) No other disease that would preclude participation in the study.