Sarcocystosis: a rare polymyositis mimic

For a diagnosis of polymyositis (PM) to be deemed probable or defi nite, affected patients must fulfil 3 or 4, respectively, of the Bohan & Peter 1975 diagnostic criteria (i.e. proximal muscle weakness, elevated muscle-specific enzyme levels, myopathic EMG and characteristic muscle histology) 1 . We report here a patient who was initially misdiagnosed and treated as having PM, and whose diagnosis of sarcocystosis myopathy was only confirmed when specialist muscle histology was undertaken in a tertiary laboratory.