Paraneoplastic dermatomyositis preceding detection of metastatic oesophageal squamous cell carcinoma after prolonged remission following pembrolizumab therapy.

Dermatomyositis is a recognised paraneoplastic inflammatory myopathy although its association with oesophageal malignancy is uncommon. Most reported cases either precede or accompany the initial diagnosis of malignancy. We report a man in his late fifties with previously treated oesophageal squamous cell carcinoma who developed florid dermatomyositis after approximately 6 years of sustained remission following chemotherapy, radiotherapy and pembrolizumab therapy. He presented with progressive proximal muscle weakness, dysphagia and characteristic cutaneous manifestations accompanied by markedly elevated creatine kinase levels. Fluorodeoxyglucose positron emission tomography-CT demonstrated metastatic oesophageal squamous cell carcinoma involving the thoracic oesophagus, abdominal lymph nodes and liver. Corticosteroids followed by paclitaxel-carboplatin rechallenge chemotherapy resulted in marked improvement in both inflammatory manifestations and tumour burden. The chronology was notable for parallel evolution of inflammatory activity and metastatic disease after prolonged oncological remission.