BACKGROUND
Miyoshi myopathy (MM) is an autosomal-recessive
muscle disorder caused by mutations in the DYSF gene. Clinical features and histopathological changes in dysferlinopathies may mimic
inflammatory myopathies and a high degree of clinical suspicion is required to guide the genetic investigation. CASE REPORT We report the case of a 16-year-old male who presented with severe bilateral calf
pain and elevated CK levels (15 000 IU/l) who was on prolonged
steroid therapy prompted by the clinical suspicion of
inflammatory myopathy. Three years into his illness, he was referred for neuromuscular evaluation presenting with untreatable
muscle pain and progressive weakness. The diagnosis of "refractory
polymyositis" was revisited. Targeted exome sequencing revealed homozygous pathogenic mutations in the DYSF gene, confirming a diagnosis of
Miyoshi myopathy. CONCLUSIONS Our case illustrates that severe
muscle pain may be the initial feature of
Miyoshi myopathy and should be considered in the differential diagnosis of
inflammatory myopathies. Although the described patient reported partial clinical improvement in
muscle pain,
steroid treatment is not an effective
therapy for
dysferlinopathy patients and it did not prevent
disease progression. In addition, we confirm the utility of next-generation sequencing approaches to
myopathies, particularly in complex or unusual cases when muscle biopsy is not available.