A genetic metabolic disorder, Galactosemia affects an individual's ability to properly metabolize the sugar galactose. In 1917, Goppert first described the disease, citing a defect in galactose metabolism that was identified by a groups led by Herman Kalckar in 1956. The disease's incidence is about 1 per 47,000 births (classic type) and is much rarer in Japan and much more common in Italy, particularly the traveler region. The disease is also very common within the Irish Traveler population. This is credited to consanguinity within a relatively small gene pool.

The enzymes needed for further metabolism of galactose are severely diminished or missing entirely among individuals affected with the disease. This leads to toxic levels of galactose to build up in the blood, resulting in hepatomegaly or an enlarged liver, cirrhosis, renal failure, cataracts, and brain damage. Mortality in infants with galactosemia is about 75% if the disease goes untreated. Treatment: The only known treatment for classic galactosemia is getting rid of lactose and galactose from the diet. Some individuals affected with the disease still experience long-term complications even with an early diagnosis and a restricted diet. Among those complications are speech difficulties, learning disabilities, neurological impairments and in girls, ovarian failure. Diagnosis: In the United States, infants are now routinely screened for galactosemia. The diagnosis is made while the person is still an infant.

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