Paraneoplastic dermatomyositis associated with Merkel cell carcinoma.

A man in his 70s presented to a dermatology outpatient clinic with a new rash developing over 4 weeks, associated with weakness and swallowing difficulties. He had a background of Merkel cell carcinoma (MCC) diagnosed 2 years prior, with a recent CT suspicious for pancreatic metastasis. On examination, there were urticated plaques involving the face, neck, back and abdomen. Gottron sign and papules, Holster sign and periorbital erythema were also present. There was proximal muscle weakness and dysphagia, requiring urgent inpatient assessment and a multidisciplinary care approach. An autoantibody screen was positive for antitranscription intermediary factor 1 (TIF1)-γ. A diagnosis of paraneoplastic dermatomyositis (DM) was made, and the patient was commenced on intravenous methylprednisolone with good response to treatment. This case highlights the need for multidisciplinary care in the management of these two rare diseases: MCC and DM. We also discuss the autoantibody anti-TIF1-γ in paraneoplastic DM.