Muscle pathology in 31 patients with calpain 3 gene mutations..

BACKGROUND AND PURPOSE: At present, more than 20 different forms of limb-girdle muscular dystrophies (LGMDs) are known (at least 7 autosomal dominant and 14 autosomal recessive). Although these different forms show some typical phenotypic characteristics, the existing clinical overlap makes their differential diagnosis difficult. Limb-girdle muscular dystrophy type 2 (LGMD2A) is the most prevalent LGMD in many European as well as Brazilian communities and is caused by mutations in the gene CAPN3. Laboratory testing, such as calpain immunohistochemistry and Western-blot analysis, is not totally reliable, since up to 20% of molecularly confirmed LGMD2A show normal content of calpain 3 and a third of LGMD2A biopsies have normal calpain 3 proteo-lytic activity in the muscle. Thus, genetic testing is considered as the only reliable diagnostic criterion in LGMD2A. MATERIAL AND METHODS: In an attempt to find a correlation between genotype and muscle pathology in limb-girdle muscular dystrophy 2A we performed histopathological investigation of a group of 31 patients subdivided according to the type of pathologic CAPN3 gene mutation. RESULTS: In all biopsies typical features of muscular dystrophy such as fiber necrosis and regeneration, variation in fiber size and fibrosis were noted. Lobulated fibers were often encountered in the muscle biopsies of LGMD2A patients. Such fibers were more frequent in patients with 550delA mutation. CONCLUSIONS: These findings may be helpful in establishing diagnostic strategies in LGMD.

Permanent muscle weakness in McArdle disease.

McArdle disease is an autosomal recessive muscle glycogenosis. In the typical clinical presentation, only exercise-related symptoms are noted. Nevertheless, permanent weakness may occur, usually late in life. In this study we report on the clinical and genetic features of fixed muscle weakness in McArdle disease. Among the 80 McArdle patients being followed at the Institute of Myology of the Salpêtrière Hospital, 9 patients have permanent weakness. The diagnosis of McArdle disease was confirmed by muscle biopsy and genetic investigations. Two patterns of muscle weakness and wasting were noted: (1) proximal and symmetric in 5 patients; and (2) asymmetric, mimicking facioscapulohumeral dystrophy (FSHD) in 4 patients. Computerized tomography scan showed fatty infiltration in the shoulder and pelvic girdle muscles. There was no clear correlation between genotype and the severity of muscle weakness. Proximal muscle weakness appeared after the age of 40 years and affected 11% of subjects in our series of 80 McArdle patients. Among patients over 40 years of age, 37.5% had muscle weakness.