A Case of Pneumocystis Pneumonia Caused by Long-Term Low-Dose Steroid Therapy

Pneumocystis pneumonia (PCP) is an opportunistic infection caused by <i>Pneumocystis jirovecii</i>. It typically occurs in patients with advanced HIV infection and severely reduced CD4+ T cell counts, but it is also seen in other immunocompromised hosts such as those receiving long-term corticosteroids, immunosuppressive agents, or chemotherapy. Common symptoms include progressive dyspnea, dry cough, and low-grade fever. In general, patients at risk for PCP who are receiving the equivalent of 20 mg/day or more of prednisolone for at least eight weeks are recommended to receive prophylactic trimethoprim-sulfamethoxazole (TMP-SMX) therapy. We report our experience of managing PCP in an 80-year-old man with a history of rheumatoid arthritis who had been receiving oral prednisolone 4 mg/day for 21 years. The patient was admitted to our hospital for rehabilitation due to disuse syndrome following surgery for aortic dissection. On hospital day one, the patient developed a fever. Oxygenation impairment was observed, prompting chest radiography and subsequent computed tomography (CT) imaging, which revealed reticular shadows and ground-glass opacities in both lung fields. These findings led to the suspicion of bacterial pneumonia and initiation of ceftriaxone therapy. By day four, his oxygen saturation dropped to 90% on room air, and laboratory tests showed a β-d-glucan level of 62.5 pg/ml. On day five, the antibiotic regimen was switched to meropenem, vancomycin, and TMP-SMX. Bronchoscopy was considered unsafe because of the patient's general condition, and sputum polymerase chain reaction (PCR) was performed instead, which was positive for <i>Pneumocystis jirovecii</i>. Based on the PCR results, clinical course, and imaging findings, a diagnosis of PCP was made. ST and atovaquone were administered for a total of three weeks, resulting in defervescence and significant improvement in oxygenation. Even low-dose corticosteroid therapy is associated with an increased risk of opportunistic infections, depending on the cumulative dose. Although our patient had been receiving only a low daily dose, the cumulative exposure indicated a high risk for infections such as PCP. In conclusion, our case experience suggests that in patients receiving long-term corticosteroid therapy, PCP and other opportunistic infections must be considered in the differential diagnosis of pneumonia, regardless of the daily corticosteroid dose received.