Clinical Presentation, Diagnosis, and Genetic Insights of Miyoshi Myopathy: A Case Report and Literature Review

Miyoshi myopathy (MM) is an autosomal recessive dysferlinopathy caused by a mutation in the dysferlin (DYSF) gene on chromosome 2p. Recent findings indicate that MM and Lower Girdle Muscular Dystrophy R2 (LGMD2B) are the same disease. We present the case of a 44-year-old male who first experienced symptoms of MM at the age of 19, initially noticing difficulty climbing stairs and standing on his toes. By the age of 29, he had developed significant calf muscle atrophy and weakness, which led to difficulties with walking. Electromyography and nerve conduction studies showed axonal damage and myogenic features. Genetic testing ruled out Charcot-MarieTooth disease but identified a pathogenic variant in the DYSF gene. Laboratory tests revealed elevated creatine kinase levels. Photographs of the patient's lower limbs showed significant calf muscle atrophy. Based on clinical, laboratory, and electrophysiological findings, he was diagnosed with MM. This case highlights the importance of genetic testing in diagnosing muscular dystrophies and underscores the need for continued research into gene and cell therapies. To the best of our knowledge, this is one of the first studies reporting a case of MM in Poland.