Diabetic myonecrosis: an unusual mimicker of idiopathic inflammatory myositis

Diabetic myonecrosis or diabetic muscle infarction (DMI), is a very rare and under-recognised complication of poorly controlled long-standing diabetes mellitus. We report a case of a 59-year-old male, who had diabetes for ten years. He presented with bilateral thigh pain of insidious onset for three months and difficulty in walking, with a similar episode in his right thigh in 2015. Creatine phosphokinase (CPK) was one and half times the normal upper limit. Magnetic resonance imaging (MRI) of his thighs showed symmetrical bulky muscles with hyperintensities on T2-weighted and short tau inversion recovery (STIR) images, supporting a clinical diagnosis of idiopathic inflammatory myositis (IIM). However, a review of histopathology slides of a muscle biopsy from the right vastus lateralis performed in 2015 showed muscle fibre ischaemic necrosis suggestive of muscle infarction. Thus a diagnosis of recurrent diabetic myonecrosis was made and the patient was treated with bed rest, opioids and aspirin with gradual recovery.