Galactose-1-phosphate uridylyltransferase galactosemia

Galactose-1-phosphate uridylyltransferase galactosemia (or type 1) is the most common type of galactosemia. It is caused by a deficiency in galactose-1-phosphate uridylyltransferase. There are two variants of the GALT gene responsible for galactosemia.
 * One variant causes so-called classic galactosemia, in which there is an extreme deficiency in galactose-1 phosphate uridyltransferase. It is an autosomal recessive condition.  The gene for GALT was mapped at 9p13.  Most serious conditions are prominent.
 * The variant gene, responsible for Duarte galactosemia, leads to about half the normal levels of GALT. Individuals with Duarte galactosemia may experience few or none of the serious symptoms of classic galactosemia.

The severity of the symptoms is dependent on a number of factors, most importantly the amount of lactose in the individual's diet. It is also possible to have one each of the classic and Duarte genes, in which case GALT activity is intermediate.