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Pneumocystis Pneumonia Complicated by Extensive Diffuse Pneumatoceles

High-resolution chest computed tomography scan before treatment (A) and after treatment (B) of Pneumocystis jirovecii pneumonia with 21-day course of trimethoprim-sulfamethoxazole and intravenous immunoglobulin.

A 60-year-old male presented to the outpatient clinic with shortness of breath, subjective fevers, and night sweats of 1-month’s duration. Initial chest X-ray revealed new bilateral perihilar consolidations. He was treated with a 5-day course of levofloxacin 750 mg/d without improvement. Therefore, he underwent a chest computed tomography (CT) scan which showed extensive bilateral pneumatoceles (Figure 1A). Bronchoscopy with bronchoalveolar lavage (BAL) was positive for Pneumocystis jirovecii on polymerase chain reaction (PCR). Laboratory workup revealed lymphopenia with lymphocyte count of 0.41 × 10(9)/L and CD4 count of 40 cells/mm3. The patient had no risk factors for HIV infection. HIV RNA testing and fourth-generation combined HIV 1/2 immunoassay for the detection of P 24 antigen and HIV 1/2 antibodies were negative on 2 separate occasions 12 weeks apart. Both tests have a sensitivity of 79.8% and 97.6%, respectively, in acute HIV infection.1 However, if acute HIV infection is suspected, HIV RNA and serologic tests should be repeated in 4-8 weeks because 99% of patients infected with HIV test positive 45 days after HIV acquisition.2 Therefore, HIV was ruled out as a cause of the patient’s lymphopenia.

Autoantibodies against granulocytes-macrophage colony-stimulating factor and interferon gamma were negative in addition to negative antinuclear antibody (ANA) and antineutrophil cytoplasmic antibody (ANCA). INVITAE© genetic panel, which includes 207 genes associated with inherited disorders of the immune system, was performed and showed 1 possibly pathogenic variant in the TNFRSF13B gene; c.542C>A (p.Ala181Glu). Changes in this gene are associated with common variable immunodeficiency. However, it was not entirely clear how this would explain the patient’s complex presentation.

He was treated with a 21-day course of trimethoprim-sulfamethoxazole at a dose of 15 mg/kg in addition to intravenous immunoglobulin (IVIG). On follow-up, the patient had near-complete resolution of the cystic lung changes with complete resolution of his symptoms (Figure 1B). CD4 lymphopenia persisted despite appropriate treatment. The current working diagnosis is idiopathic CD4 lymphopenia with hypogammaglobinemia.

Pneumocystis jirovecii pneumonia (PCP) is a potentially life-threatening fungal infection that occurs almost exclusively in patients who are immunocompromised.3 Patients often have nonspecific symptoms including dyspnea and low-grade fevers. Bilateral diffuse interstitial opacities are typically seen on imaging with ground-glass opacities being the dominant feature.4 However, a minority of patients present with pneumatoceles. This is particularly less common in patients not infected with HIV with an incidence as low as 3% and is often reversible with treatment.5 The pathogenesis is not well understood. Proposed theories include inflammatory exudates acting as a one-way valve leading to cyst formation, elastase release from macrophages leading to destruction of alveolar septa, and direct tissue damage caused by Pneumocystis jirovecii.6

This is less commonly encountered now because of the increased awareness of pneumocystis infections in patients without HIV, and the improved diagnostic tests resulting in early diagnosis and treatment. Pneumocystis jirovecii pneumonia should be considered in patients presenting with pneumatoceles.

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-Hasan Ahmad Hasan Albitar, MDaOmar M. Abu Saleh, M.B.B.S.b

This article originally appeared in the May 2019 issue of The American Journal of Medicine.

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