Prenatal and postnatal diagnostic difficulties in a family with rare alleles of the galactose-1-phosphate uridyl transferase locus.

Whole-blood galactose-1-phosphate uridyl transferase (Gal-PUT) (EC 2.7.7.12) activity was absent in a newborn boy with galactosaemic symptoms. The symptoms disappeared on a galactose free diet. In the next pregnancy prenatal diagnosis was performed. Gal-PUT activity was measured by isotope technique and Gal-PUT genotype was determined by gel electrophoresis. The mother was shown to be heterozygous Duarte/heterozygous Los Angeles, the father heterozygous Duarte/heterozygous galactosaemia. The fetus had the same genotype as the father. A normal girl without galactosaemic symptoms was born. Reinvestigation of the index case showed that he was also heterozygous Duarte/heterozygous galactosaemia. It is concluded that the activity of Gal-PUT should always be measured by isotope technique to prove the diagnosis of heteditary galactosaemia. Furthermore, Gal-PUT-genotyping in families with rare alleles is essential for safe prenatal diagnosis.