The inflammatory myopaties such as polymyositis (PM) and dermatomyositis (DM) are autoimmune inflammatory muscle disorders characterised by the development of proximal and often symmetrical muscle weakness. Levels of serum muscle enzymes such as creatine kinase (CK), lactate dehydrogenase (LDH), asparate aminotransferase (AST) and alanine aminotransferase (ALT) are usually elevated. However, high levels of AST, ALT and LDH, without a determination of CK, are often misdiagnosed with hepatic diseases. Conversely, concomitant elevations of AST, ALT and LDH along with CK in patients with PM and DM may be considered to be due to myopathy itself even in a case of coexistence of liver injury. Oral administration of prednisolone was begun at a dose of 60 mg/day, resulting in a good outcome.