Pembrolizumab: Anti-melanoma differentiation-associated gene 5 (MDA5)-positive pauci-myopathic dermatomyositis, hypothyroidism and severe diarrhoea.

A 64-year-old man developed anti-melanoma differentiation-associated gene 5 (MDA5)-positive pauci-myopathic dermatomyositis, hypothyroidism, and severe diarrhea after receiving pembrolizumab for squamous cell lung cancer. The patient had a history of arterial hypertension and chronic allergic contact dermatitis. He experienced hypothyroidism, dyspnea, exacerbation of eczema, myalgia, and muscle weakness. The diagnosis of anti-MDA5-positive pauci-myopathic dermatomyositis was made, and treatment with pembrolizumab was discontinued. The patient later developed severe diarrhea and hypokalemia, leading to the discontinuation of pembrolizumab again. Overall, the patient's condition improved with treatment. [Extracted from the article]