Case history

A 73 year old lady was referred with a four week history of proximal muscle weakness, myalgia and an erythematous, oedematous rash affecting her face, upper chest, and back. Systemic enquiry and general examination was otherwise unremarkable. Initial investigations revealed a normal full blood count, erythrocyte sedimentation rate, C reactive protein, urea and electrolytes, liver function test, thyroid function tests, and urine analysis. The creatine kinase (CK) was increased to 3806 (normal range 24–170 U/l). Although Mi-2 antibody testing was not carried out she did have an IgG ANA level of 100. The rest of the autoimmune screen was negative. A needle muscle biopsy showed type 2-fibre atrophy with perivascular inflammatory changes but no direct evidence of myositis.

She was given high dose oral prednisolone (60 mg daily) and received two pulses of intravenous methylprednisolone (1 g) and cyclophosphamide (1 g). Although the CK level responded rapidly to this treatment her clinical response was more gradual. Azathioprine was introduced and the prednisolone dose was gradually reduced to 30 mg daily with plans to reduce the dose further by 5 mg/month. She had a normal chest radiograph, sigmoidoscopy, barium enema, and abdominal ultrasound.

Three months after the onset of her dermatomyositis she was seen urgently with acute thoracolumbar back pain. Radiographs confirmed slight vertebral wedging of D12. A myeloma screen and biochemical bone profile were normal. An isotope bone scan showed increased activity at D12 …