Pneumocystis Jiroveci Pneumonitis: A Rare Pneumonia in a Patient Treated with Chemoimmunotherapy

Abstract

Introduction: Immune-related adverse events occur in 20% of cases of treated with checkpoint inhibitor agents and require immunosuppressive agents depending upon the severity. This leads to increased vulnerability to opportunistic infections such as Pneumocystis Jiroveci pneumonia (PJP). Here we present a patient with stage four Non small cell lung cancer (NSCLC) who underwent 4 cycles of chemoimmunotherapy with Carboplatin, Pemetrexed and Pembrolizumab. Subsequently, the patient was found to have PJP pneumonia. Case presentation: A 71-year-old Caucasian male, known to have hypertension, T2DM and stage 4 NSCLC (s/p right lower lobectomy) was being treated with palliative chemoimmunotherapy: carboplatin, pembrolizumab and pemetrexed. He completed 4 cycles. Pembrolizumab was discontinued in March 2020 due to concern for myositis. However, Pemetrexed maintenance was continued and he received his last and sixth dose in October 2020. He presented with worsening dyspnea and nonproductive cough for 1 month without any h/o fever, sweats or chills. CT chest showed new diffuse bilateral ground-glass infiltrates with no pleural effusion or consolidation compared to a negative CT PE study one month earlier. COVID 19 testing was negative. He was given Solu-Medrol 1 g for 3 days, however he didn't improve. Initial differentials were checkpoint inhibitor pneumonitis, drug-induced pneumonitis, pulmonary alveolar proteinosis, unrecognized hypersensitivity pneumonitis, cryptogenic organizing pneumonia, and unlikely pneumocystis pneumonia or diffuse alveolar hemorrhage. The respiratory array test was negative. Sputum PCR was positive for Pneumocystis Jiroveci and he was started on Trimethoprim-Sulfamethoxazole (TMP-SMX) and Prednisone. TMP-SMX was continued for 21 days. The patient improved but required readmission, more steroids, and underwent bronchoscopy with BAL which confirmed the resolution of PJP infection. He was then treated for HAP and subsequently was discharged. Discussion: Immune suppression is very well known with standard chemotherapeutic agents.PJP infection is rarely encountered in patients with NSCLC and has a low incidence of 2.6 per 100,000 person-years. Sputum PCR has increased sensitivity to conventional stain approximately 100%. However, specificity varies depending upon the population: 20% colonization rate in healthy adults. The risk of this infection is associated with chemoradiotherapy, corticosteroids, and immunosuppression. Multiple similar case presentations have been reported in literature, with similar occurrence in lung cancer patients being treated with pemetrexed, pembrolizumab and methotrexate containing regimen. Although rare, we must keep PJP as a differential in NSCLC patients undergoing treatment with chemoimmunotherapy and presenting with pneumonia.