Multiminicore myopathy

Multiminicore myopathy (also known as multiminicore disease, multicore myopathy, or minicore myopathy) is a rare inherited muscle disorder classified among the congenital myopathies. It is characterized by the presence of multiple small areas of disrupted structure (called minicores or multicores) within muscle fibers, visible on muscle biopsy. The disease primarily affects skeletal muscles, leading to muscle weakness and hypotonia (reduced muscle tone), typically presenting in infancy or early childhood. Several clinical forms have been described, including the classic form (the most common), which features axial muscle weakness, scoliosis, and respiratory insufficiency; a form with prominent external ophthalmoplegia (weakness of eye muscles); a form with hand involvement and joint contractures; and a moderate form with generalized weakness. The classic form of multiminicore myopathy is most frequently caused by recessive mutations in the SEPN1 (selenoprotein N) gene or the RYR1 (ryanodine receptor 1) gene. Mutations in RYR1 can also cause other forms of the disease. Less commonly, mutations in MYH7 and other genes have been implicated. The disease predominantly affects the musculoskeletal and respiratory systems. Patients often present with delayed motor milestones, proximal and axial muscle weakness, spinal rigidity, scoliosis, and progressive respiratory compromise that may require ventilatory support. Facial weakness and feeding difficulties may also occur in early life. Cardiac involvement is uncommon but has been reported in certain genetic subtypes. There is currently no cure for multiminicore myopathy, and treatment is supportive and multidisciplinary. Management focuses on physical therapy and rehabilitation to maintain mobility, orthopedic interventions for scoliosis, and respiratory monitoring with ventilatory support when needed. Nutritional support may be required in patients with feeding difficulties. Regular cardiac screening may be recommended depending on the genetic subtype. Genetic counseling is important for affected families. With appropriate supportive care, many patients maintain ambulation, though the clinical course and severity can vary significantly depending on the underlying genetic cause and clinical subtype.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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