A Duarte variant with clinical signs

Galactosemia: screening and diagnosis

Galactose is normally metabolized to glucose through the coordinated activities of three enzymes: galactokinase, galactose-1-phosphate uridyl transferase (GALT), and uridine diphospho-glucose 4-epimerase (epimerase). High concentrations of galactose and their metabolites are toxic to mammals. Hereditary deficiencies of galactokinase and of GALT and perhaps rarely of epimerase cause clinical disorders that can be prevented by early recognition and institution of a galactose-free diet. The genetics of disorders of galactose metabolisms and the methods used currently for their detection are reviewed. Future prospects in the diagnosis of these disorders are discussed.

Prenatal diagnosis of galactosaemia in six pregnancies -- possible complications with rare alleles of the galactose 1-phosphate uridyl transferase locus

We describe our experience in prenatal diagnosis of six foetuses at risk for galactosaemia. In one family the parents were both shown to be double heterozygotes at the galactose 1-phosphate uridyl transferase (Gal-PUT) locus, the mother having a Duarte/Los Angeles and the father a Duarte/galactosaemia genotype. The foetus (and an older brother previously thought to have classical galactosaemia) was also a Duarte/galactosaemia double heterozygote. In the other five families, the parents and three foetuses were heterozygous carriers of the galactosaemia gene, one of the foetuses had galactosaemia, and one was homozygous for the normal gene. It is concluded that by a combination of family studies and assay of cultured amniotic cell Gal-PUT, accurate prediction of the foetal Gal-PUT genotype is now possible.

Galactose-1-phosphate uridyl transferase deficiency due to Duarte/galactosemia combined variation: clinical and biochemical studies

The most common abnormality detected by the screening of newborn infants for galactosemia is a deficiency of galactose-1-phosphate uridyl transferase due to the presence in one individual of allelic genes for the Duarte variant and for galactosemia. Clinical studies of ten untreated individuals with this genetic compound, including three adults, failed to reveal evidence of cataracts, liver disease, or mental subnormality, the major clinical complications associated with galactosemia. Galactose-1-phosphate was not detectable in umbilical cord blood from one infant. Galactose was not detectable in random blood specimens from any of the individuals and was present in only small amounts following ingestion of milk in one infant and a child. It would appear that this common gentic variation is usually, if not always, benign.

'Durate variant with clinical signs' has alpha1 -antitrypsin genotype ZZ

A patient with neonatal jaundice and cirrhosis who was previously reported homozygous for the Durate variant of galactose-1-phosphate uridyl transferase has the ZZ genotype for alpha1-antitrypsin. A sister of the patient, also with ZZ genotype, is less severly affected with liver disease and is a heterozygote for the Durate variant. Since a number of patients with ZZ genotype of alpha1-antitrypsin have been previously reported to have liver disease, the latter genotype is the more probable explanation for the patients' clinical state. A question is raised, however, whether the Duarte variant may be specifically associated with the development of liver disease in ZZ individuals.

Uridine monophosphate kinase: A new genetic polymorphism with possible clinical implications

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