Immune Reconstitution Inflammatory Syndrome-like Condition Associated with Pneumocystis jirovecii Pneumonia During Folinic Acid Treatment in a Rheumatoid Arthritis Patient

A 94-year-old woman with rheumatoid arthritis who had been treated with low-dose methotrexate was referred to our hospital because of a 3-day history of a fever and pancytopenia. With a diagnosis of febrile neutropenia of unknown origin, empirical antibiotic treatment and folinic acid therapy were initiated. Despite a recovery from pancytopenia, the high fever remained, and dyspnea developed. She was clinically diagnosed with Pneumocystis jirovecii pneumonia (PCP) and successfully treated with trimethoprim/sulfamethoxazole and adjunctive corticosteroid therapy. Folinic acid treatment effectively brought about rapid immune recovery but might have led to a clinical manifestation of PCP resembling immune reconstruction inflammatory syndrome.