Study of a family with both galactosemic and Duarte variants of galactose-1-phospho uridyl transferase

Maple syrup urine disease: two different forms within a single family

A family is reported in which the index case presented with an acute form of maple syrup urine disease (MSUD), whereas two of her sisters and her father were found to have an almost asymptomatic form of the disease. It is proposed that the members of this family are compound heterozygotes for the classical deficient mutant gene and for a "variant" allele.

Galactose intolerance in individuals with double heterozygosity for Duarte variant and galactosemia

The most frequent cause for an abnormal result during screening of newborn infants for galactosemia is double heterozygosity for Duarte variant and galactosemia, in which galactose-1-phosphate uridyl transferase activity is reduced to approximately 17% of normal. Thirty-nine oral galactose tolerance tests were performed in 27 infants and children with this condition. In comparison to age-matched controls, all children with this genetic variant reached much higher levels of blood galactose and galactose-1-phosphate following oral galactose challenge. The integrated plasma galactose response increased with the age of the child, whereas integrated erythrocyte galactose-1-phosphate responses were elevated to the same degree at all ages. Although all children appeared clinically normal, the marked abnormalities in the ability to dispose of ingested galactose raise questions concerning appropriate dietary recommendations for such children.

Isoelectrofocusing of erythrocyte galactose 1 phospho uridyl transferase in a family with both galactosemia and Duarte variants

A family with the presence of the genes for both galactosemia and the Duarte variant is described. Galactose 1 phospho uridyl transferase has been studied not only by electrophoresis on starch gel, but also by isoelectro-focusing on thin-layer acrylamide. Normal and variant transferases were resolved into three bands, the isoelectric point of which was between 5.40 and 5.10 for the normal subjects, and between 5.25 and 4.95 for subjects with the Duarte variant.

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.

Galactose-1-phosphate accumulation by a Duarte-transferase deficiency double heterozygote

An infant, suspected of having galactosemia following a positive screening test on dried blood spots, was shown to be a Duarte-transferase deficiency compound heterozygote through studies of electrophoretic mobility of the transferase enzyme in blood from the patient and family members. No rise in blood glucose was seen following oral ingestion of galactose. At the same time, galactose rose in plasma and was excreted in the urine; galactose-1-phosphate accumulated in erythrocytes. A galactose-free diet was considered the prudent course in the presence of the patient's inability to metabolize galactose completely.