The authors present an account of a rare idiopathic relapsing form of focal myositis affecting the left musculus rectus bulbi inferior in 22-year-old female patient. The clinical course of the disease and possibilities of its diagnosis are described. The differential diagnosis of focal myositis is also discussed. The authors emphasize the necessity of treatment of idiopathic focal myositis with prednisone and the need of dispensary care of these patients as approximately one third, unless treated, develop generali- zed forms of polymyositis with a variable prognosis.

        Key words: focal myositis, differential diagnosis, CT, NMR, creatine kinase, generalised polymyositis,