Pneumocystis, Jiroveci Pneumonia



Pneumocystis, Jiroveci Pneumonia


Jud W. Gurney, MD, FACR





Key Facts


Terminology



  • Opportunistic fungal infection often affecting individuals with T-cell immunodeficiency


Imaging Findings



  • Ground-glass is dominant finding; opacities symmetric and diffuse with sparing of lung periphery (40%)



    • Mosaic attenuation pattern (30%)


    • Upper lobe distribution in some, may be associated with aerosolized pentamidine prophylaxis


  • Cysts (30%), thin-walled, usually in ground-glass opacities


  • Prior irradiated lung protected: PCP will develop only outside radiation ports


  • Extremely rare to have PCP with normal HRCT examination


Top Differential Diagnoses



  • Hypersensitivity Pneumonitis


  • Lymphocytic Interstitial Pneumonia


  • Diffuse Alveolar Hemorrhage


Pathology



  • Patients with impaired cell-mediated immunity predisposed to PCP


  • Organism can be found in normal lungs


  • Even with highly active antiretroviral therapy (HAART), PCP remains most prevalent opportunistic infection in AIDS


Clinical Issues



  • Nonproductive cough (75%), fever (75%), dyspnea (65%), and hypoxia


  • Appropriately treated PCP has very good prognosis







Axial CECT shows diffuse ground-glass opacities image with lobular sparing. Small holes image may represent early pneumatoceles.






Coronal CECT reconstructions shows diffuse perihilar distribution of ground-glass opacities image and small pneumatoceles image.


TERMINOLOGY


Abbreviations and Synonyms



  • Pneumocystis pneumonia (PCP)


Definitions



  • Opportunistic fungal infection often affecting individuals with T-cell immunodeficiency



    • 2 major forms: Trophozoites and cysts


IMAGING FINDINGS


General Features



  • Best diagnostic clue: Diffuse symmetric ground-glass opacities in hypoxic immunocompromised patient


  • Patient position/location



    • Diffuse perihilar with peripheral sparing


    • Less common upper lobe predominant with cysts


  • Morphology: Ground-glass opacities with cysts (30%)


CT Findings



  • Morphology



    • Ground-glass is dominant finding



      • Diffuse infections (predominantly PCP) is most common cause of isolated diffuse ground-glass opacities


    • Superimposed intralobular and smooth interlobular septal thickening less common, results in “crazy-paving” pattern


    • Cysts (30%)



      • Thin-walled, usually in ground-glass opacities


      • Usually upper lobe distribution


      • Predispose to pneumothorax


      • With successful treatment, resolve over 5 months


      • Rarely described in non-AIDS PCP


    • Atypical patterns (5-10%) such as multiple nodules (some with cavitation), asymmetric consolidations or rarely, dominant reticular opacities



      • Multiple nodules (may cavitate)


      • Asymmetric consolidation


      • Reticular (interlobular and intralobular) opacities rarely dominant finding


  • Distribution



    • AIDS



      • Ground-glass opacities symmetric and diffuse with sparing of lung periphery 40%


      • Mosaic attenuation pattern 30%



      • Upper lobe distribution in some; may be associated with aerosolized pentamidine prophylaxis


    • Non-AIDS: Often spares 1 lung zone (upper, middle, lower)


    • Prior irradiated lung protected: PCP will develop only outside radiation ports


  • Other



    • Adenopathy uncommon (10%), short axis diameter > 1 cm



      • More common with other fungal or tuberculous infection


    • Tree-in-bud pattern not present



      • Consider bacterial pneumonia, aspiration, or endobronchial tuberculosis


    • Pleural effusion rare


  • In AIDS, confidant diagnosis can be made in 95%


Radiographic Findings



  • May be normal


  • Spontaneous pneumothorax in patients with AIDS = Pneumocystis pneumonia


Nuclear Medicine Findings



  • Historically, gallium scan used for questionable cases, now replaced by CT due to long imaging times (24 hours)



    • Widespread lung activity is present with PCP


Imaging Recommendations



  • Best imaging tool: Extremely rare to have PCP with normal HRCT examination


DIFFERENTIAL DIAGNOSIS


Hypersensitivity Pneumonitis



  • Antigen source identified with careful work and personal history



    • Onset of dyspnea and nonproductive cough tends to be more subacute or chronic


    • Hypoxia often more mild and fever less common


  • Diffuse ground-glass most common imaging manifestation


  • Ill-defined centrilobular nodules more common than in PCP


  • Air-trapping common at expiratory CT, uncommon with PCP


  • May also have cysts


Lymphocytic Interstitial Pneumonia



  • Increased frequency in AIDS, especially in children


  • Thin-walled cysts, ground-glass opacities, and centrilobular nodules


  • Lymph nodes may be enlarged, uncommon with PCP


Diffuse Alveolar Hemorrhage



  • Anemia common


  • Clinical history, tissue sampling, and laboratory investigation required to differentiate different etiologies of DAH


  • Diffuse or extensive bilateral ground-glass and consolidative opacities similar to PCP


Cytomegalovirus Pneumonitis

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Pneumocystis, Jiroveci Pneumonia

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