LGMD2B

LGMD2B, or limb-girdle muscular dystrophy type 2B, is a rare genetic disorder characterized by progressive muscle weakness and degeneration, primarily affecting the muscles of the hips, thighs, pelvis, shoulders, and upper arms. It falls under the broader category of limb-girdle muscular dystrophies (LGMD), a group of inherited muscle diseases that share similar clinical features but differ in genetic causes and progression.

LGMD2B is caused by mutations in the CAPN3 gene, which encodes the enzyme calpain-3. Calpain-3 plays a role in muscle fiber maintenance and repair, and its dysfunction leads to muscle fiber breakdown and weakness. The condition is inherited in an autosomal recessive manner, meaning an individual must inherit two copies of the mutated gene—one from each parent—to develop the disorder. Parents who carry one mutated copy are considered carriers but typically do not exhibit symptoms.

Symptoms of LGMD2B usually appear in late childhood or adolescence, though the age of onset can vary. Early signs may include difficulty running, climbing stairs, or rising from a seated position, as well as muscle cramps and stiffness. Over time, muscle weakness progresses, affecting mobility and potentially leading to mobility aids like wheelchairs. Respiratory and cardiac complications can also develop in advanced stages, though these are less common than in other forms of muscular dystrophy.

Diagnosis involves a combination of clinical evaluation, genetic testing to confirm CAPN3 mutations, and muscle biopsy to assess muscle fiber pathology. There is currently no cure for LGMD2B, but treatments focus on managing symptoms, such as physical therapy to maintain muscle strength and function, orthopedic interventions for joint deformities, and respiratory support if needed. Research into gene therapy and other experimental treatments is ongoing, offering potential future advancements for affected individuals.

The prognosis for individuals with LGMD2B varies depending on the severity of muscle involvement and the rate of disease progression. While the condition is progressive, many individuals can lead active lives for several decades with appropriate medical and supportive care. Genetic counseling is recommended for families with a history of LGMD2B to assess inheritance risks and family planning options.