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Cryptococcal Pneumonia vs. PCP in Immunocompromised Hosts
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Burke A. Cunha, Professsor of Medicine State University of New York School of Medicine, Stony Brook
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llusardi{at}winthrop.org Burke A. Cunha
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Dear Sir: I read with interest the article by Dr. Chang et al on pulmonary cryptococcosis describing the differences between cryptococcal pneumonia (CP) in normal/ compromised hosts.1 However, the common clinical problem is to differentiate CP from Pneumocystis (carinii) jiroveci pneumonia (PCP) in immunocompromised hosts. Immunocompromised hosts on immunosuppressive therapy are predisposed to either CP or PCP. Immunocompromised hosts with diffuse infiltrates often require transbronchial/lung biopsy to differentiate CP from PCP.2 A key differentiating point between CP and PCP is the presence/absence of an oxygen diffusing defect. An increased A-a gradient (>30) is characteristic of PCP but not CP. The A-a gradient is an important way to differentiate PCP from other acute diffuse infiltrates in immunosuppressed hosts, i.e., fungal/ tuberculous pneumonias, pulmonary hemorrhage, heart failure etc.2, 3 Pathologically, CP and PCP resemble each other, i.e., both are PAS and silver stain positive.4, 5 The microscopic appearance on lung biopsy of C. neoformans is much larger (2-15µm) and has more morphologic variability than PCP which is smaller (3-µm)/uniform in size and often present in clumps. Capsules demonstrated by mucicarmine stain are diagnostic of CP. During silver stain preparation, C. neoformans capsules are destroyed, but a clear “halo” surrounds the organisms. The absence of a capsule/halo readily differentiates PCP from CP. If budding is present in lung biopsy specimens, C. neoformans is confirmed since PCP has no budding forms. 4, 5 The radiologic/microbiological features of PCP and CP in immunocompromised hosts can help in their differentiation. The most useful clinical finding is the presence/absence of an, ? A-a gradient (>30) which favors PCP vs. CP. Microbiologically/pathologically, the most important differences, differentiating PCP from CP are the presence/absence of a capsule, size/morphological variation, and budding 4, 5. Burke A. Cunha, MD Chief, Infectious Disease Division Winthrop-University Hospital, Mineola, New York and Professor of Medicine State University of New York School of Medicine Stony Brook, New York REFERENCES 1. Chang W et al, Ching T, Hsu, HH, Lee SC, Huang, KL, Tung, HJ, Chen, CY. Pulmonary Cryptococcosis* Comparison of Clinical and Radiographic Characteristics in Immunocompetent and Immunocompromised Patients. Chest Journal 2006; 129: 333-340 2. Rubin RH, Greene R: Clinical approach to the compromised host with fever and pulmonary infiltrates. In Rubin RH, Young LS (eds): Clinical Approach to Infection in the Compromised Host, ed 3. New York, Plenum Medical Book Company, 1994 3. Cunha, BA. Pneumonias – its compromised hosts. Infectious Disease Clinics of North America 2001; 15: 591-612 4. Beneke ES, Rogers AL. Medical Mycology and Human Mycoses.1996 Belmont (CA), Star Publishing Co. 1996 5. Cunha, BA. PCP vs Cryptococcal Pneumonia. Infectious Diseases Practice 2006; 30: 118-120 |
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