Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Pneumocystis jirovecii Pneumonia
- Radiologic Findings
- Fig 1. Chest PA shows haziness in bilateral lower lung zones and cystic changes in bilateral upper lung zones.
Fig 2. CT scan reveals patchy ground-glass opacities and consolidation in both lungs, predominantly involving the lower zones. Cysts or pneumatoceles are seen in both lungs, predominantly involving the upper zones. A cavitary nodular lesion is also seen in the right upper lobe.
- Brief Review
- After the diagnosis of Pneumocystis pneumonia through wedge resection of the left lung, the patient was tested for HIV, and the result returned positive.
Pneumocystis jiroveci is an atypical fungus that infects almost exclusively the pulmonary alveoli and causes pneumonia in immunocompromised human hosts, particularly those with a deficiency in cell-mediated immunity. Since intraalveolar macrophages serve as the primary host defense against P. jiroveci, macrophage deficiency or dysfunction can lead to infection. CD4+ T lymphocytes, which decrease during HIV infection, are essential for eradicating P. jiroveci infection. Thus, P. jiroveci pneumonia (PCP) is the most common opportunistic infection among AIDS patients. PCP occurs primarily among persons who are unaware of their HIV infection.
Other susceptible patients include bone marrow transplant recipients, those with hematologic malignancies, those undergoing chemotherapy for malignancy, and those undergoing long-term corticosteroid therapy for inflammatory and connective tissue diseases.
The most common symptoms of PCP are dyspnea and non-productive cough. In patients who are profoundly immunocompromised, onset may be more dramatic and resemble other pulmonary infections. However, the presentation is usually non-specific and insidious.
The diagnosis can often be confirmed with bronchoalveolar lavage.
Chest radiographic findings of PCP are non-specific, and one-third of infected patients may have normal radiographic findings. HRCT may be indicated in the evaluation of immunocompromised patients with normal chest radiographic findings. Features suggestive of PCP in patients with CD4+ T lymphocyte counts below 200/mm3 include small pneumatoceles, subpleural blebs, fine reticular interstitial changes, and predominantly perihilar lesions.
HRCT is sensitive and can be used to exclude PCP in patients with clinical suspicion of PCP but who have normal chest radiographs. Extensive ground-glass opacity (GGO) or GGO predominantly involving the perihilar or mid zones is the principal finding in PCP, reflecting the accumulation of intraalveolar fibrin, debris, and organisms. There may be a mid, upper, or lower zone predilection depending on whether the patient is receiving prophylactic aerosolized medication. Other features include reticular opacities, septal thickening, and pneumatocele (~30%). Pleural effusion is rare, and lymphadenopathy is uncommon (10%).
Atypical features, found more frequently in patients treated prophylactically, include consolidation, nodules, lymphadenopathy, and pleural effusion. Consolidation is more common in patients without HIV infection and tends to develop more rapidly, reflecting pulmonary damage from the host immune response. Nodules may cavitate and usually indicate the presence of intercurrent infectious bronchiolitis from other organisms.
The cystic form of PCP is also more frequent in patients receiving prophylaxis. In this pattern, thin-walled cysts or pneumatoceles are found in both lungs with upper lobe predominance, which increases the risk of pneumothorax due to cyst rupture.
Patients with moderate to severe infections are treated with trimethoprim-sulfamethoxazole combined with corticosteroids. These agents may be used as prophylactic agents. Overall, with prompt treatment, survival is good (50%–95%), although relapses are common.
- Please refer to
Case 727, Case 797, Case 823, Case 948, -
- References
- 1. Jeffrey P. Kanne, Donald R. Yandow, Cristopher A. Meyer. Pneumocystis jiroveci Pneumonia: High-Resolution CT Findings in Patients With and Without HIV Infection. AJR 2012; 198:W555-W561.
2. Hidalgo A, Falcó V, Mauleón S et-al. Accuracy of high-resolution CT in distinguishing between Pneumocystis carinii pneumonia and non- Pneumocystis carinii pneumonia in AIDS patients. Eur Radiol. 2003;13 (5): 1179-84.
3. Maffessanti M, Polverosi R, Dalpiaz G et-al. Diffuse lung diseases, clinical features, pathology, HRCT. Springer Verlag. (2006) ISBN:8847004292.
- Keywords