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Pneumocystis pneumonia (PJP) is caused by Pneumocystis jiroveci and is an important infection of chronically immunocompromised patients, especially those receiving higher doses of corticosteroids and those with abnormalities in cell-mediated immunity. Until recently, the vast majority of cases were in HIV patients. This has changed with an increasing proportion occurring in non-HIV patients, including in solid organ and hematopoietic stem cell transplant recipients. The risk factors, clinical presentation, and response to therapy in such patients are different than in HIV. Patients are particularly vulnerable during the initial months after transplant and at times of intensification of immunosuppression for treatment of rejection and graft-versus-host disease (GVHD). Effective prophylaxis for 6–12 months after transplant and during time of treatment for acute rejection (or GVHD) all but eliminates the risk during those periods. PJP now tends to occur in patients not receiving effective prophylaxis during high-risk periods. Reasons include persistence of intense immune compromise beyond the typical prophylaxis periods, failure to prescribe prophylaxis, non-adherence, and occasionally breakthrough infection. Clinical manifestations tend to be more abrupt and severe than in those with HIV, and prompt treatment is imperative. Empiric therapy is often warranted, but establishing the diagnosis is important to limit unnecessary exposure to potentially toxic therapy and potentially lifetime secondary prophylaxis. Traditional tests (staining of induced sputum and bronchoalveolar lavage fluid) continue to be a mainstay of diagnosis, now complemented by nucleic acid testing of respiratory tract specimens and serum beta-D-glucan assays.

DOI: 10.1007/978-3-030-01751-4_48-1