Sarcoplasmic body myopathy--a rare hereditary myopathy with characteristic inclusions.

OBJECTIVES: To characterise a Swedish family with a rare hereditary myopathy with unique sarcoplasmic inclusion bodies in the muscle biopsy. MATERIALS AND METHODS: Part of the pedigree was described in 1980. Nine new members of the included and the phenotype further characterised through clinical, neurophysiological and radiological investigations. RESULTS: Six of the nine subjects displayed clinical and/or laboratory evidence of myopathy with sarcoplasmic inclusions. CONCLUSIONS: Sarcoplasmic body myopathy is distinguished from other distal myopathies by a more malignant course and early involvement of thenar muscles and hand flexors. Five to ten years after onset the affected subjects develop distal, as well as proximal, weakness and atrophy and the majority require a wheelchair after ten to fifteen years of disease. The disorder is manifested through elevated creatine kinase levels and the presence of the pathognomonic sarcoplasmic inclusions prior to clinical signs and symptoms.