Two new polymorphisms in the arylsulfatase A gene and their haplotype associations with normal, metachromatic leukodystrophy and pseudodeficiency alleles

Linkage disequilibrium exists between metachromatic leukodystrophy (MLD) and pseudodeficiency mutations and selected polymorphisms within the arylsulfatase A gene. We have identified 2 new polymorphic NlaIII sites, NlaIII1 and NlaIII2, in the gene that, when used in combination with the known BsrI and BamHI polymorphisms, extends the haplotype associations of the pseudodeficiency and the most common infantile onset MLD alleles. Fixed haplotypes have also been established for 3 other recurring MLD mutations, ala212val, pro426leu, and thr274met. The NlaIII2 site is relatively rare and was found only in association with the pseudodeficiency variant carrying the glycosylation site mutation alone.