Limb-Girdle Muscular Dystrophy Type 2F

Abstract

LGMD2F is clinically characterized by limb-girdle weakness, cardiomyopathy, and respiratory impairment. Since it is caused by mutations in the SGCG gene, encoding the delta-sarcoglycan protein (Table 14.1), it belongs to the group of disorders named sarcoglycanopathies, in which a mutation in any one sarcoglycan gene results in the secondary deficiency of the entire sarcoglycan complex. In most populations, delta-sarcoglycanopathy is the least common type of sarcoglycanopathy. LGMD2F was first reported in four Brazilian families, where all the affected patients share the same homozygous mutation, resulting in the premature truncation of the protein. Two additional American patients were reported with nonsense mutations and clinical symptoms consistent with Duchenne muscular dystrophy: one 9-year-old girl had facial weakness, mild wasting of proximal muscles in upper and lower extremities, scapular winging, and slight decrease in proximal muscle strength and became wheelchair dependent at age 14; another girl had frequent falls, toe walking, large calves, and difficulty with stairs at age 22 months. Few other cases have been reported, but all the LGMD2F patients reported so far show a Duchenne-like phenotype, with complete absence of the whole sarcoglycan complex in muscle.