Fukutin-related limb-girdle muscular dystrophy R13

Fukutin-related limb-girdle muscular dystrophy R13 (LGMD R13, formerly LGMD2M) is a rare autosomal recessive muscular dystrophy caused by mutations in the FKTN (fukutin) gene. This gene encodes a protein involved in the glycosylation of alpha-dystroglycan, a key component linking the muscle cell cytoskeleton to the extracellular matrix. When fukutin is deficient or dysfunctional, alpha-dystroglycan is hypoglycosylated, leading to impaired structural integrity of skeletal muscle fibers. LGMD R13 belongs to the group of dystroglycanopathies, which represent a spectrum of disorders ranging from severe congenital forms (such as Walker-Warburg syndrome and muscle-eye-brain disease) to milder limb-girdle phenotypes. Patients with LGMD R13 typically present with progressive proximal muscle weakness affecting the shoulder and pelvic girdle muscles, leading to difficulty with activities such as climbing stairs, rising from a seated position, and lifting the arms overhead. Onset is variable but often occurs in childhood or adolescence. Serum creatine kinase (CK) levels are usually markedly elevated. Some patients may also exhibit mild cardiac involvement, respiratory insufficiency, or subtle central nervous system abnormalities, though the limb-girdle form is generally milder than the congenital presentations associated with FKTN mutations. Muscle biopsy typically shows dystrophic changes with reduced immunostaining for glycosylated alpha-dystroglycan. There is currently no cure for LGMD R13. Management is supportive and multidisciplinary, including physical therapy to maintain mobility and prevent contractures, respiratory monitoring and support when needed, cardiac surveillance, and orthopedic interventions as appropriate. Corticosteroids are not a standard treatment for this condition. Research into gene therapy and strategies to restore alpha-dystroglycan glycosylation is ongoing but remains in early stages.

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