Galactokinase Deficiency

A number sign (#) is used with this entry because galactokinase deficiency is caused by homozygous or heterozygous mutation in the GALK1 gene (604313) on chromosome 17q24.

Classic galactosemia (230400) is a distinct disorder caused by mutation in the gene encoding galactose-1-phosphate uridyltransferase (GALT; 606999) on chromosome 9p13.

Description

Galactokinase deficiency is an autosomal recessive disorder that causes cataract formation in children not maintained on a lactose-free diet. Cataract formation is the result of osmotic phenomena caused by the accumulation of galactitol in the lens (Asada et al., 1999).

Clinical Features

Gitzelmann (1967) reported juvenile cataracts related to galactokinase deficiency in 2 sibs of a consanguineous Gypsy family, Fanconi had previously reported the cases as instances of 'galactose diabetes;' however, GALT activity in red cells was normal. There was no mental retardation. Several close relatives had reduced red cell galactokinase activity, suggesting that they were heterozygotes.

Cook et al. (1971) described an affected newborn, ascertained because of hyperbilirubinemia, who had resolution of the cataracts with dietary management. Segal et al. (1979), who studied affected brothers, suggested that mental retardation may occur with galactokinase deficiency.

Prachal et al. (1978) associated presenile cataracts with heterozygosity for galactokinase deficiency and galactose-uridyl transferase deficiency.

Bosch et al. (2002) reviewed the clinical features of galactokinase deficiency in describing 55 patients in 25 publications. Cataract was reported in most patients. Clinical abnormalities other than cataract were reported in 15 (35%) of 43 cases for which information was available. However, all symptoms were reported infrequently and a causal relationship with the galactokinase deficiency could not be determined. Pseudotumor cerebri is a rare but consistently reported abnormality in this disorder.

Molecular Genetics

In 2 patients with galactokinase deficiency and cataracts, Stambolian et al. (1995) identified 2 different homozygous mutations in the GALK1 gene (604313.0001; 604313.0002). One of the patients had been reported by Pickering and Howell (1972).

In affected members of 6 Romani (Gypsy) families from Bulgaria with galactokinase deficiency, Kalaydjieva et al. (1999) identified a homozygous mutation in the GALK1 gene (P28T; 604313.0003). The authors concluded that this mutation was most likely responsible for the galactokinase deficiency in the cases originally described by Gitzelmann (1967).

Asada et al. (1999) identified 5 mutations in the GALK1 gene in 7 unrelated Japanese patients with galactokinase deficiency.

Population Genetics

Mayes and Guthrie (1968) found 6 heterozygotes for galactokinase deficiency among 642 persons in Buffalo, N.Y.

In Italy, Magnani et al. (1982) estimated the heterozygote frequency to be 1 in 310; 2 persons presumably heterozygous by biochemical criteria were detected among 620 persons studied.