Sarcoglycanopathies.

The so-called sarcoglycanopathies form a subgroup of four genetically closely related autosomal recessive limb-girdle muscular dystrophies (LGMD2C-F) caused by mutations of the α-, β-, γ-, and δ-sarcoglycan genes. All four sarcoglycans are glycosylated transmembrane proteins and form a tetrameric complex that is part of dystrophin-associated proteins. The clinical phenotype associated with sarcoglycanopathies is characterized by a slowly progressive proximal muscle weakness with onset during childhood in most cases. The disease course is often similar but more variable than X-linked Duchenne muscular dystrophy. Diagnosis is usually based on muscle biopsy findings that confirm dystrophic changes and deficiency of one or more sarcoglycan proteins. Genetic testing is used to confirm the diagnosis. A number of different animal models have been developed to study the function of sarcoglycans and to develop specific therapeutic strategies such as gene transfer, but so far none of these techniques has entered clinical practice. Therefore, treatment is symptomatic and aims at amelioration of locomotor, respiratory, and cardiac manifestations of the disease.