Muscle weakness with a hidden cause.

Idiopathic inflammatory myopathies (IIM) represent a diverse group of systemic autoimmune disorders characterised by skeletal muscle weakness with variable clinical manifestations.Dermatomyositis (DM) is a heterogeneous IIM and is associated with progressive muscle weakness, with characteristic skin features, and with an increased risk of malignancy. Here, we report a previously healthy man in his early 40s who presented to the emergency department with a 14-day history of symmetric progressive proximal muscle weakness. Both upper arms were painful and swollen, and they displayed marked weakness in arm elevation. Climbing stairs was no longer possible due to muscle weakness and pain. A facial and truncal rash as well as periungual erythema were noted. Laboratory analysis revealed highly elevated creatine kinase. Based on these findings, the diagnosis of DM was confirmed. A comprehensive search for malignancy revealed a non-palpable pure seminoma. While DM as a paraneoplastic phenomenon of seminoma is extremely rare, our case underlines the importance of a thorough tumour search.