Background Dermatomyositis (DM) is an idiopathic inflammatory myopathy. Like polymyositis (PM), it is a rare disorder with prevalence rates estimated at about 1 per 100,000 in the general population. There is a female to male predominance of about 2:1 in adults. The peak occurs in the fifth decade, although all age groups may be affected. DM (and PM to a lesser extent) has been known to be associated with cancer. Estimates of the frequency of cancer in adults with DM/PM range from 7 to 34%. There have been several reports of improvement of myositis following successful treatment of the malignancy, as well as worsening of the myositis associated with cancer recurrence. So far, very few cases of large cell carcinoma associated DM have been reported.
Case Report We present a case of a 50-year-old gentleman who presented to us with generalized worsening pain and stiffness for 2 months. He also noticed a rash on the elbows and knuckles, which had appeared since the onset of increasing stiffness. Positive laboratory values: ESR 38, AST/ALT 333/104, LDH 715, CK 28,258, TSH 2.4, ANA positive (1:160 speckled pattern), aldolase 34.4 (normal 0-7). A CT scan of the chest was performed in view of the diagnosis of dermatomyositis. There was a 4.2 cm by 3 cm retrocaval mass with areas of necrosis and few mediastinal lymph nodes. There was a filling defect in the right pulmonary artery with recanalization suggestive of a chronic pulmonary embolus with multiple pleural-based wedge-shaped densities suggestive of pulmonary infarcts. A biopsy of the mediastinal lymph nodes revealed a metastatic anaplastic carcinoma of the large cell type. The patient received chemotherapy with carboplatin and docetaxel and radiotherapy, anticoagulation for pulmonary embolism, and steroids for DM.
Discussion DM, a rare disorder of the dermatologic and musculoskeletal system, is often the harbinger of malignancy. A systematic search for occult malignancy should be carried out in patients diagnosed with DM. Mortality is due to progression of underlying malignant disease. This underscores the potential harmful effects of delayed diagnosis of malignancy in patients with DM. Investigations may include CT scans of the chest, abdomen, and pelvis, along with endoscopy of the gastrointestinal tract. Investigations of the genitourinary tracts and breast may be undertaken depending on individual cases.
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