When presented with accumulated galactose, this enzyme reduces the aldehydic end group and produces galactitol, the analogous sugar alcohol. This compound exerts osmotic pressure within the lens because it diffuses very slowly. While patients deficient in galactokinase accumulate galactitol in the liver at rates comparable to those patients with transferase-deficient galactosemia, only the latter show evidence of hepatic damage. Hence, it is apparent that much remains to be learned about the pathophysiologic implications of galactose metabolic impairment. Accordingly, the data are insufficient to provide an accurate assessment of incidence, although the estimated range is 1 case per 50,000-100,000 live births.
Morbidity is limited to cataract formation.
Mental retardation and hepatic damage are not associated with galactokinase deficiency. As an autosomal recessive condition, the disorder is distributed equally between genders. Because galactokinase deficiency is a genetic disease, it is present from conception and may be revealed at birth by the presence of congenital cataracts. Failure to develop a social smile or to follow objects may be initial signs of visual deficit due to cataracts. GI symptoms associated with ingestion of galactose are conspicuously absent.