Recent Advances in the Diagnosis and Management of Pneumocystis Pneumonia

Abstract

In human immunodeficiency virus (HIV)-infected patients, Pneumocystis jirovecii pneumonia (PCP) is a wellk-nown opportunistic infection and its management has been established. However, PCP is an emerging threat to immunocompromised patients without HIV infection, such as those receiving novel immunosuppressive therapeutics for malignancy, organ transplantation, or connective tissue diseases. Clinical manifestations of PCP are quite different between patients with and without HIV infections. In patients without HIV infection, PCP rapidly progresses, is difficult to diagnose correctly, and causes severe respiratory failure with a poor prognosis. High-resolution computed tomography findings are different between PCP patients with HIV infection and those without. These differences in clinical and radiological features are due to severe or dysregulated inflammatory responses that are evoked by a relatively small number of Pneumocystis organisms in patients without HIV infection. In recent years, the usefulness of polymerase chain reaction and serum β-D-glucan assay for rapid and non-invasive diagnosis of PCP has been revealed. Although corticosteroid adjunctive to anti-Pneumocystis agents has been shown to be beneficial in some populations, the optimal dose and duration remain to be determined. Recent investigations revealed that Pneumocystis colonization is prevalent and that asymptomatic carriers are at risk for developing PCP and can serve as the reservoir for the spread of Pneumocystis by airborne transmission. These findings suggest the need for chemoprophylaxis in immunocompromised patients as well as infection control measures, although the indications remain controversial. Because a variety of novel immunosuppressive therapeutics have been emerging in medical practice, further innovations in the diagnosis and treatment of PCP are needed.

Keywords: Chemoprophylaxis; Immunocompromised Host; Infection Control; Loop-Mediated Isothermal Amplification; Pneumocystis jirovecii Pneumonia.

Figure 1. High-resolution computed tomography findings of Pneumocystis jirovecii pneumonia (PCP). (A) PCP in a patient with rheumatoid arthritis receiving methotrexate therapy. Diffuse ground-glass opacity (GGO) is distributed in a panlobular manner, in which GGO is sharply demarcated from the adjacent lung by interlobular septa. (B) PCP in a patient with human immunodeficiency virus infection. Diffuse GGO is distributed in an inhomogeneous manner without sharp demarcation. Subpleural sparing is also indicated. (C) PCP in a patient with malignant lymphoma. Among GGO, patchy consolidation is located along the bronchovascular bundle. (D) PCP in a cancer patient who was receiving chemotherapy and high-dose corticosteroid. Cysts are observed within the affected area, suggesting that they were formed by PCP.