GALACTOSEMIA - RELATIONSHIP OF IQ TO BIOCHEMICAL CONTROL AND GENOTYPE

The long-term outlook for galactose-1-phosphate uridyl transferase deficiency (McKusick 230400) is poor. Although affected individuals who are treated with a galactose-free diet from early childhood usually progress to adulthood, they are frequently intellectually impaired and women often have ovarian dysfunction. The neuropsychological outcome does not appear to relate to the time of diagnosis and commencement of treatment (Waggoner et al 1990). The variability in outcome has been hypothesized to relate to genotype. The transferase gene has recently been mapped to chromosome 9p13 and a number of mutant alleles have been identified in patients with classical galactosaemia. One particular mutation (Q188R) has been found with a high frequency in both British and North American populations (Dunger and Holton 1994). A previous study has examined the relationship between intellectual functioning and the presence of the Q188R mutation, but in that study details of galactose-1-phosphate (gal-1-P) exposure were unknown (Kaufman et al 1994). We have investigated the relationship between IQ, the presence of the Q188R mutation and exposure to gal-1-P in patients with galactosaemia in the northwest region of England.