Group of inherited enzyme deficiencies which feature elevations of galactose in the blood; this condition may be associated with deficiencies of galactokinase, udp glucose-hexose-1-phosphate uridylyltransferase (classic form), or udp glucose 4-epimerase; the classic form presents in infancy with failure to thrive, vomiting, and intracranial hypertension; affected individuals also may develop mental retardation, jaundice, hepatosplenomegaly, ovarian failure and cataracts.

Galactosemia (British galactosaemia, from Greek γαλακτόζη + αίμα, meaning galactose + blood, accumulation of galactose in blood) is a rare genetic metabolic disorder that affects an individual's ability to metabolize the sugar galactose properly. Galactosemia follows an autosomal recessive mode of inheritance that confers a deficiency in an enzyme responsible for adequate galactose degradation. Friedrich Goppert (1870–1927), a German physician, first described the disease in 1917, with its cause as a defect in galactose metabolism being identified by a group led by Herman Kalckar in 1956...