Patients with ANO5 mutations may present not only limb-girdle muscular dystrophy type 2L or adult-onset Miyoshi-type myopathy but also with asymptomatic hyperCKemia, exercise intolerance, or rhabdomyolysis. In this study, data from 38 patients in France with ANO5 mutations with and without muscle weakness on first examination were compared. The authors found that creatine kinase (CK) levels ranged from 200 to 40,000 U/L. Electromyography showed a myopathic pattern in 5 patients, and muscle imaging showed involvement of posterior calf muscles in 10. Mild cardiac involvement was observed in 2. Sixteen remain free of weakness after a median follow-up period of 5 years. Asymptomatic, sometimes mild, hyperCKemia or exercise intolerance is a presentation of ANO5-related myopathy and may remain isolated or precede muscle weakness by many years.
