CD4 and B-cell acute lymphoblastic leukemia: Here we report the first case, to our knowledge, of PJP in a patient with a CD4+ T cell count of >200/μL after CAR-T cell therapy.<h4>Case</h4>A 14-year-old girl developed hemophagocytic lymphohistiocytosis (HLH) after cord blood transplantation (CBT) for relapsed precursor B-cell acute lymphoblastic leukemia (B-ALL).