[Sarcoglycanopathies].

Identification of several clinical pictures in relation to a deficit of various protein components of the sarcoglycan complex, has allowed a new classification to be established for muscular dystrophies, correlating the protein alpha, beta, gamma, sigma deficit with a type of girdle dystrophy ('Limb-Girdle Muscular Dystrophy', LGMD) and the genomic identification respectively: 2D/17, 2E/4q12, 2C/13q12, 2E/4q12, 2F/5q33. The correlation between the various proteins and complexes and the dystrophin is known as Dystrophin Associated Glycoproteins (DAG) and Dystrophin Related Proteins (DRP). This interrelationship is fundamental to the study of the different components and the key to immunohistochemical study and evaluation amongst other things. Patients with alpha-sarcoglycan deficiency (LGMD 2D) show great clinical and genetic heterogeneity sometimes leading to severe degrees of muscular dystrophy similar to Duchenne muscular dystrophy. The mutation R77C is a recurrent mutation and the cause in over one third of the patients with this deficiency. Absence of gamma-sarcoglycan is also a cause of severe muscular dystrophies with the Duchenne phenotype. It has been described in the Mediterranean region, Japan and Brazil. The delta 525T mutation is the commonest and also, as occurs with C283Y (specific to the gypsy race), is a foundational mutation. Deficit of beta-sarcoglycan (LGMD 2E) gives rise to different grades of clinical severity, frequently with cardiac involvement. At present the phenotype of sigma-sarcoglycan deficit (LGMD 2F) has yet to be described [REV NEUROL 1999; 28: 150-3].