Dermatomyositis and pemphigus vulgaris: association or coincidence?

A 76-year-old woman presented with a pruritic photodistributed rash and dysphagia. Serum anti-nuclear antibody was positive (titre 1/1280) and skin and muscle biopsies confirmed a diagnosis of dermatomyositis. She was treated with oral prednisolone (5-50 mg/day), mometasone furoate 0.1% ointment and lotion, and tacrolimus 0.03% ointment. Four years later she presented with multiple painful scaly erosions on the face, scalp and trunk. Histopathology and direct and indirect immunofluorescence confirmed a diagnosis of pemphigus vulgaris. Repeated malignancy screens were negative. She was treated with methotrexate (10 mg/week) and prednisolone (50 mg/day slowly tapered to 5 mg/day), with good control of both diseases.