EVIDENCE OF A GENETIC-MARKER ASSOCIATED WITH EARLY-ONSET IN FRIEDREICHS ATAXIA

We evaluated the association between age at onset of Friedreich's atax ia and alleles of two restriction fragment length polymorphisms (RFLP) at D9S15 and D9S5 in the 9q13-9q21.1 region. We studied 65 Italian pa tients from 49 families. Age at onset was not normally distributed in our patients, suggesting allelic heterogeneity. Patients homozygous fo r allele 1 of MspI RFLP detected by probe MCT112 at D9S15 (M1) had an earlier onset (mean 9.3, SD 3.4 years) than patients homozygous for al lele 2 (M2; mean 12.1, SD 4.3). Heterozygotes had an onset age similar to that of the M2 homozygotes. These findings suggest that the M1 all ele might be a marker of one allelic early-onset Friedreich's ataxia m utation.