OVERVIEW OF DISTAL MYOPATHIES - FROM THE CLINICAL TO THE MOLECULAR

Five distinct predominantly distal myopathies have been identified wit h discrete clinical and genetic patterns as follows: (1) Welander myop athy (late adult onset, type 1), with autosomal dominant inheritance a nd unknown molecular localization; (2) Markesbery-Griggs/Udd myopathie s (late adult onset, type 2), with autosomal dominant inheritance and linkage to chromosome 2q; (3) Nonaka myopathy (early adult onset, type 1), with autosomal recessive inheritance and molecular localization t o 9p1-q1. Nonaka myopathy is identical to quadriceps-sparing familial inclusion body myopathy; (4) Miyoshi myopathy (early adult onset, type 2), with autosomal recessive inheritance and localization to 2p; (5) Laing myopathy (early onset, type 3), with autosomal dominant inherita nce and linkage to chromosome 14. The gene and abnormal gene product h ave not yet been defined for any of the distal myopathies. However, it is already clear that disorders allelic to the distal myopathies can begin with proximal weakness. Given such major phenotypic variation, i t is possible that some of the diseases we regard as distal myopathies may become obsolete. Instead, these conditions may become known by th eir genetic mutation or abnormal gene product, much like Duchenne and Becker dystrophy. (C) 1998 Elsevier Science B.V. All rights reserved.