Metagenomic Next-Generation Sequencing in Diagnosis of a Case of Pneumocystis jirovecii Pneumonia in a Kidney Transplant Recipient and Literature Review

BACKGROUND: Despite the increasing incidences of Pneumocystis jirovecii pneumonia (PCP) in renal transplant recipients, diagnosis of PCP remains challenging due to its nonspecific clinical presentation and the inadequate performance of conventional diagnostic methods. There is a need for novel diagnostic methods. CASE PRESENTATION: A 27-year-old woman developed acute pneumonia 4 months after renal transplantation. Blood tests revealed a low CD4 count, a normal 1,3-beta-D-glucan level and other changes typical of inflammatory responses. Chest imaging showed bilateral diffuse infiltrates. Microscopic examination of stained sputum and bronchoalveolar lavage fluid (BALF) smear specimens did not find Pneumocystis organisms. There was also no evidence for other pathogens known to cause pneumonia in various antibody and culture tests. Direct metagenomic next-generation sequencing (mNGS) analysis of a BALF specimen identified a large number of P. jirovecii reads, allowing to confirm the diagnosis of PCP. Following treatment with trimethoprim-sulfamethoxazole for two weeks, the patient was cured and discharged. CONCLUSION: This case report supports the value of mNGS in diagnosing PCP, highlights the inadequate sensitivity of conventional diagnostic methods for PCP, and calls for the need to add PCP prophylaxis to the current Diagnosis and Treatment Guideline of Invasive Fungal Infections in Solid Organ Transplant Recipients in China.