The three major categories of the idiopathic inflammatory myopathies are dermatomyositis, polymyositis, and inclusion body myositis.1 The most important clinical feature distinguishing inclusion body myositis from dermatomyositis and polymyositis is the lack of responsiveness to immunosuppressive treatment.1 2 Yet, it is the experience of many clinicians that a small subgroup of patients with inclusion body myositis show at least a partial response to immunosuppressive treatment. There are no specific characteristics which can identify this subgroup. In this report we present an anti-Jo-1 positive patient with inclusion body myositis who showed a marked and sustained clinical improvement after treatment with oral prednisone.

A 74 year old man, with no relevant medical history, presented with a slowly progressive proximal muscle weakness of the lower limbs. On presentation there were no complaints of muscle weakness of the upper limbs, dysphagia, myalgia, arthralgia, or feelings of general malaise. He denied any sensory symptoms. His family history was negative for neuromuscular or rheumatic disorders and he did not use any myotoxic drugs.

Physical examination showed asymmetric proximal and distal muscle weakness (muscle strength in MRC grades: neck flexors 3, right and left triceps 4, right and left iliopsoas 4, right and left gluteus maximus 4, right quadriceps 4, left quadriceps 2.5, right and left hamstrings …