Pneumocystis pneumonia in a patient with rheumatoid arthritis treated with methotrexate: A case report

Rationale: Pneumocystis jirovecii pneumonia (PCP) is an opportunistic and life-threatening pulmonary infection observed in patients receiving immunosuppressive treatment. In rheumatoid arthritis (RA) patients, methotrexate (MTX) is a risk factor for PCP. However, it is difficult to clinically differentiate between RA-related interstitial pneumonia, MTX-related interstitial pneumonia, and PCP. Patients concerns: An 88-year-old Japanese woman with a 4 years history of RA was admitted to our hospital with shortness of breath. She was initially treated with salazosulfapyridine (1000 mg/day). However, her active arthritis had been refractory and she was treated with MTX (8 mg/week) at 20 months before current presentation. Diagnosis: High-resolution chest computed tomography demonstrated diffuse ground-glass opacities distributed throughout the middle and lower lobes, predominantly in the right lung. Although serum β-D-glucan (BDG) level was low, the patient was clinically diagnosed with PCP based on the positive result in polymerase chain reaction for P. jirovecii DNA using the sputum sample. Intervention: The patient was immediately treated with trimethoprim–sulfamethoxazole and high-dose prednisolone, which successfully improved pulmonary shadows and respiratory failure. Outcomes: The patient’s respiratory symptoms including hypoxia improved. On day 11, the patient developed trunk pruritus and rashes, prompting a transition from trimethoprim/sulfamethoxazole to atovaquone. On day 14, chest CT showed complete resolution of the ground-glass opacities. The patient was discharged from our hospital on the 21th day. Lessons: Evidence regarding the diagnostic testing for PCP in patients with RA is insufficient. Measurement of BDG levels is useful for the early diagnosis of PCP in human immunodeficiency virus-infected patients. However, BDG levels should be carefully judged when PCP is suspected in RA patients receiving MTX. Progressive respiratory distress should be considered to be a consequence of PCP, and physicians should consider establishing an early diagnosis and treatment intervention for PCP in patients with RA receiving MTX.