Urine and plasma galactitol in patients with galactose-1-phosphate uridyltransferase deficiency galactosemia

Urinary excretion of galactitol was determined in 95 normals (N/N), 67 gala ctosemic (G/G), and 39 compound heterozygotes for the Duarte and galactosem ia genotype (D/G). Galactitol excretion is age-dependent in both normal ind ividuals and patients with classic galactosemia on lactose-restricted diets . In galactosemic patients who are homozygous for the Q188R mutation, urina ry galactitol levels were fivefold to 10-fold higher than those of normal s ubjects of comparable age. All but a few patients with classic galactosemia with the Q188R mutation and another mutant G allele had urinary excretion comparable to the Q188R homozygous patients. African-American galactosemic patients with the S135L mutation of the galactose 1-phosphate uridyltransfe rase (GALT) gene also excreted abnormal quantities of galactitol. Most subj ects with a Duarte allele and a G allele excrete normal amounts of the suga r alcohol. There is a correlation between galactitol excretion and red bloo d cell (RBC) galactose-1-phosphate (gal-1-P). Plasma galactitol was also el evated in galactosemic patients (3.4 to 23.2 mu mol/L; undetectable in norm al individuals). In contrast to the decrease in urinary galactitol with age , plasma levels remain in a narrow concentration range with no significant difference with age. Urine and plasma galactitol distinguish galactosemic p atients from normals. In addition, urinary galactitol excretion may be an i mportant parameter for the assessment of steady-state galactose metabolism in galactosemia. Copyright (C) 1999 by W.B. Saunders Company.