A large deletion together with a point mutation in the GALC gene is a common mutant allele in patients with infantile Krabbe disease.

Galactocerebrosidase (GALC) activity is deficient in all patients with globoid cell leukodystrophy (GLD). While most patients have the severe infantile form of this autosomal recessive disorder (Krabbe disease), patients up to 50 years of age have been diagnosed in this laboratory. With the cloning of the GALC cDNA and availability of information regarding the gene organization, patients can be evaluated for their disease-causing mutations. We now report that a large deletion, together with a polymorphic C to T transition at position 502 of cDNA (counting from the A of the initiation codon), is responsible for a large number of disease-causing alleles in patients with Krabbe disease. Of 48 patients evaluated, 10 were found to be homozygous for the 502/del allele, five patients were heterozygous for this allele, 21 patients were heterozygous for the 502 mutation (presence of the deletion could not be confirmed), and one infantile patient was homozygous for the 502 mutation but at least one allele was not deleted. No patient was found to have the deletion without the 502 polymorphism. The delineation of mutations causing infantile Krabbe disease will provide new information regarding structure-function relationships in this multi-subunit enzyme and will improve the identification of patients and carriers in some families.