Clinical characteristics of Pneumocystis jirovecii pneumonia in non-HIV patients by metagenomic next-generation sequencing

Objective To investigate the clinical features of patients with Pneumocystis jirovecii pneumonia (PJP) diagnosed by metagenomic second-generation sequencing. Methods A total of nine PJP patients who were admitted to Department of Respiratory and Critical Care Medicine, the Affiliated Hospital of Xuzhou Medical University from January 1, 2021 to September 30, 2021 and diagnosed by second-generation sequencing using bronchoalveolar lavage fluid (BALF) were selected and their clinical data were retrospectively analyzed. Their clinical manifestations, laboratory examination indicators, imaging performance, other basic diseases, treatment and outcome, and the etiology of metagenomic next-generation sequencing (mNGS) were observed. Results Among the nine PJP patients, there were seven men and two women, aged 17—70 years, with an average age of 54±15 years. There were eight patients with basic diseases and one without basic disease. Four patients took oral hormones and immunosuppressants for a long time, while only two patients were given long-term oral hormones alone. Their clinical manifestations included fever, cough, and dyspnea. According to chest CT scan, patch shadow was menifested, most of which were accompanied by ground glass density shadow, together with multiple nodular shadows and honeycomb shadows. Nine PJP patients presented hypoxemia, with an average oxygenation index of (185±82) mmHg, and their peripheral blood lymphocyte counts decreased, with an average value of (0.88±0.39) ×10⁹/L, where eight cases showed significant decreases in CD4⁺ T lymphocyte count, with an average value was (250±187) cells/μl, and remarkable increase in (1, 3)-β D-dextran level and lactate dehydrogenase level, with the averages of (347±193) ng/L and (819±420) U/L, respectively. Among the nine patients, Pneumocystis jirovecii were detected by mNGS in the BALF of five patients (55.6%), in both the sputum and mNGS of four patients (44.4%). Two patients were Pneumocystis jirovecii positive in the sputum alone, but diagnosed with PJP, based on typical clinical and imaging menifestation. Furthermore, other viruses, multidrug-resistant bacteria and other fungi were detected. After treatment with compound sulfamethoxazole and carboplafencin, four cases improved and five cases died. Conclusions Non-HIV-infected immunosuppressed patients suffer from a variety of underlying diseases of PJP, which is related to administration of glucocorticoids and immunosuppressants. The severity of the disease is severe, and mixed opportunistic infections are common, with a high case fatality rate. Compared with conventional laboratory tests, mNGS has high sensitivity and specificity, and may be an effective diagnosis method for PJP.