A 53-year-old woman presented with proximal muscle weakness and myalgia in her upper and lower limbs. She was recently diagnosed with advanced ovarian cancer involving abdominal carcinomatosis. Her medication included therapeutic dalteparin for a tumor-associated ovarian vein thrombosis. Physical exam revealed proximal muscle weakness with a V-neck and Shawl sign. Laboratory results showed elevated creatinine kinase and positive antinuclear antibodies. Myositis panel returned negative. Skin biopsy and EMG were both compatible with dermatomyositis.