Galactosemia is an autosomal recessive disorder caused by pathogenic variants in the gene GALT. While it is a pan-ethnic disease, it is found more commonly in patients from certain ethnicities, including African-Americans and Irish Travelers. Patients with galactosemia are unable to break down the sugar galactose, which is a major component of lactose, the sugar found in breast milk and formula. Therefore, infants with galactosemia who are on a diet that includes lactose will develop lethargy and jaundice, feeding difficulties and will fail to gain weight. Sepsis and death may occur if galactose is not removed from the diet. With removal of galactose, affected children may still experience long-term complications, including cataracts, developmental delay, or intellectual disability. Adult women may also experience premature ovarian failure. With proper treatment, affected individuals will have a normal life expectancy. For patients with classical galactosemia, there is no known genotype-phenotype correlation.
For information about carrier frequency and residual risk, please see the residual risk table.