MUCOPOLYSACCHARIDOSIS TYPE-I (HURLER SYNDROME) - LINKAGE DISEQUILIBRIUM INDICATES THE PRESENCE OF A MAJOR ALLELE

Two polymorphism exist in the alpha-L-iduronidase (IDUA) gene, the gene that is defective in mucopolysaccharidosis type I (MPS I), viz. a KpnI polymorphism and a variable number of tandem repeats (VNTR) polymorphism with three common alleles. The analysis of allele and haplotype frequencies for these two polymorphism in the normal population and in MPS I patients revealed the presence of linkage disequilibrium. The frequency of the 2,2 (VNTR, KpnI) allele in MPS I patients was 57% compared with only 37% in the normal population. The implications for the presence of a major MPS I allele and the ability to predict patient phenotype are discussed.