Pathologically elevated blood galactose levels may occur because of deficient functioning of enzymes involved in galactose metabolism (e.g., GALK (galactokinase), GALT (galactose-1-phosphate uridyl transferase), or UDP-Galactose-4 epimerase (GALE)), a rare condition known as galactosemia [132]. The gene discussed is GALK1; the disease is classic galactosemia.