We report a unique case of a 65-year-old man with squamous-cell NSCLC and high PD-L1 expression (80%), who developed a rare complication: radiation recall pneumonitis (RRP), with superimposed Pneumocystis jirovecii pneumonia and severe symptomatic hyponatremia induced by trimethoprim/sulfamethoxazole (TMP-SMX). Here, CD274 is linked to pneumocystosis.