Galactosemia is a rare, inherited genetic disorder caused by high levels of galactose in the blood. Galactose is a part of the sugar (lactose) found in dairy products. Galactosemia is caused by a deficiency in one of the three enzymes needed to break down galactose, so it builds to dangerous levels.

A child who has galactosemia appears normal at birth but develops symptoms after taking formula or breast milk. Symptoms of galactosemia include:

• Loss of appetite.
• Vomiting.
• Diarrhea.
• Poor weight gain.

Without early diagnosis and treatment, a child with galactosemia can develop mild to severe effects. The child may stop developing normally and may have vision problems (cataracts), liver problems, and intellectual disabilities. One form of the disease causes cataracts without intellectual disabilities or poor growth.

Galactosemia is treated with a special diet that does not contain galactose or lactose. A person who has galactosemia must always avoid milk and milk products.