MAIN CLINICAL-FEATURES OF THE 3 MAPPED AUTOSOMAL RECESSIVE LIMB-GIRDLE MUSCULAR-DYSTROPHIES AND ESTIMATED PROPORTION OF EACH FORM IN 13 BRAZILIAN FAMILIES

Autosomal recessive limb-girdle muscular dystrophies (AR LGMD) represe nt a group of muscle diseases with a wide spectrum of clinical signs, varying from very severe to mild. Four different loci that when mutate d cause the AR LGMD phenotype have been mapped or cloned or both: in t wo of them the linked families seem to have a relatively mild phenotyp e (LGMD2a and LGMD2b), in the third one the reported linked families s how a more severe clinical course (LGMD2c), while mutations in the fou rth locus may cause severe or mild phenotypes (LGMD2d). The relative p roportion of each of these genetic forms among the LGMD families and w hether there are other genes that when mutated cause this phenotype is unknown. The closest available informative markers for each of the ma pped AR LGMD genes have been tested in 13 Brazilian families with at l east three affected patients. The findings from the present report con firm nonallelic heterogeneity for LGMD and suggest that in our populat ion about 33% of the LGMD families are caused by mutations in the 15q gene, 33% in the 2p gene, 17% by mutations in the adhalin gene, and le ss than 10% may be by mutations at the 13q locus. They also suggest th at there is at least one other gene responsible for this phenotype. In addition, the main clinical features of the different forms are discu ssed.