Paraneoplastic syndrome and underlying breast cancer: a worsening rash despite initiation of chemotherapy.

Skin may show the first clinical evidence of systemic disease and can be the first clue to malignancy in 1% of cases. Dermatomyositis is an immunologically mediated inflammatory myopathy characterized by proximal muscle weakness, muscle inflammation, and characteristic skin findings. It has an incidence of 1 in 100,000 patients. In 15%-30% cases of dermatomyositis, an underlying malignancy is the cause of paraneoplastic syndrome. Ovarian and breast cancer in women and lung cancer in men are the most common malignancies associated with dermatomyositis. Here we report the case of a 55-year-old postmenopausal woman who initially presented with a facial rash. She was treated for chemical dermatitis without resolution of symptoms and was subsequently found to have dermatomyositis associated with stage IV invasive ductal carcinoma of the breast. In most cases, the skin changes resolve after treatment for the underlying malignancy has been initiated, but in this case of paraneoplastic dermatomyositis, the rash worsened with initiation of treatment for underlying breast cancer.