Abstract
A 72-year-old man with locally advanced lung squamous cell carcinoma experienced red purpura on the lower legs and hematuria when the disease progressed during definitive chemoradiotherapy. He had renal dysfunction and proteinuria. Biopsy specimens of the skin lesion and kidney revealed immunoglobulin A vasculitis. Potential causes such as paraneoplastic syndrome and cancer treatment have been proposed. The administration of steroids rapidly improved the symptoms. The presentation of immunoglobulin A vasculitis is accompanied by malignancies. Clinicians should keep this syndrome in mind, even during curative-intent treatment.