Galactokinase deficiency is a rare mild form of galactosemia characterized by early onset of cataract and an absence of the usual signs of classic galactosemia, i.e. feeding difficulties, poor weight gain and growth, lethargy, and jaundice. The disease is galactokinase deficiency (MONDO_0009255, a Monarch Disease Ontology identifier). Also known as: GALK deficiency, GALK-D, galactokinase deficiency galactosemia, galactokinase deficiency with cataracts, galactosemia II, galactosemia type 2.