Primary thyroid lymphoma presenting as dermatomyositis: a first case and review of the literature.

A 55-year-old woman presented with a 3-week history of weakness. On examination, she had a heliotrope rash, V-neck and shawl signs. There was symmetric proximal muscle weakness, and 2/5 strength in upper and lower extremities. Laboratory values showed CK 5836, CRP 14.9, erythrocyte sedimentation rate 49, lactate dehydrogenase 633, negative antinuclear antibodies and anti-Jo1 antibodies. Muscle biopsy and immunohistochemistry findings were consistent with dermatomyositis. Treatment with high-dose steroids, cyclophosphamide and intravenous immunoglobulin (IVIG) was started, without improvement of symptoms. She was found to have cold agglutinins with a cold screen titre of 1:256,256. Work up for malignancy ensued. Positron emission tomography-computed tomography (PET-CT) showed increased uptake in the thyroid. Fine-needle thyroid biopsy with flow cytometry studies revealed atypical lymphocytes consistent with diffuse large B-cell lymphoma. The patient underwent R-CHOP therapy, with remarkable improvement of her symptoms. Dermatomyositis associated with primary thyroid lymphoma has not been previously reported. This case reinforces the importance of cancer screening in dermatomyositis patients. 2016 BMJ Publishing Group Ltd.