Pneumocystis jirovecii Pneumonia (PCP) in a Non-HIV Lung Cancer Patient in the Absence of Common Risk Factors

Pneumocystis jirovecii pneumonia (PCP) has been described mainly in AIDs and in immunocompromised patients with hematological malignancies, organ transplant recipients, collagen vascular disease, and primary immune deficiencies or those under treatment with steroids or chemotherapy. The incidence of PCP pneumonia is increasing in solid organ tumors and hematological malignancies receiving chemotherapy. Pneumocystis pneumonia has been rarely reported in patients with non-small cell lung cancer (NSCLC). We describe a 68-year-old woman with a recent diagnosis of squamous cell lung cancer, who received radiotherapy two weeks prior to the current hospital admission with shortness of breath and dry cough. The initial investigations, including chest X-ray and CT images, were suggestive of atypical pneumonia, with PCP pneumonia as the top differential. Treatment was started with high-dose trimethoprim-sulfamethoxazole (cotrimoxazole) and oxygen support. Serum beta-glucan was found to be more than 500 pg/ml in favor of PCP infection. Oral steroids were added to the treatment in view of hypoxia (arterial oxygen pressure (PaO2) < 70 mmHg) requiring high-flow nasal cannula support. Subsequently, bronchoscopy was done and the bronchoalveolar lavage (BAL) sample came positive for PCP polymerase chain reaction (PCR). The patient made a significant recovery after four weeks of treatment with cotrimoxazole and was discharged home in stable condition with cotrimoxazole prophylaxis. The reported cases of PCP pneumonia in lung cancers were following chemotherapy, chemoradiation, or steroid treatment.The incidence of PCP pneumonia in lung cancer patients receiving radiotherapy is relatively rare. Our patient could not tolerate chemotherapy for the cancer due to an anaphylactic reaction and hence was treated with radiotherapy alone for the lung cancer prior to getting PCP pneumonia. Therefore, it is important to carry a high index of suspicion for PCP infection in a lung cancer patient presenting with features of atypical pneumonia following cancer treatments, including radiotherapy alone.