The combination of GI (colitis) and MSK (arthritis and polymyalgia-like syndrome) irAEs was observed in diverse malignancies (sarcomatoid carcinoma of the lung, pancreatic cancer, and gastric cancer) and treatment types (single-agent PD-1, combination PD-L1 and CTLA-4 in combination with chemotherapy, and two different single-agent PD-1 inhibitors [funding related]). The gene discussed is CTLA4; the disease is lung sarcomatoid carcinoma.