Infect > Granuloma > Nocardia

Nocardia:

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Clinical:

Nocardia is a gram-positive and weakly acid fast aerobic organism found in soil and decaying vegetation. Most cases of pulmonary infection are caused by N. asteroides (N. asteroides accounts for approximately 85% of all nocardial infections and most pulmonary infections [4]). Infection is common in immune compromised hosts (particularly those with impaired cell mediated immunity [4]), diabetics, and patients receiving high dose corticosteroids. Other risk factors for infection include: Immunosuppression (following organ transplant, esp. cardiac transplantation), alveolar proteinosis, HIV infection [4], and lymphoreticular malignancy (leukemia, lymphoma). The reported incidence of nocardial infection in solid organ transplant patients varies from 0.7-3.5% [4].

Patients generally present with cough, fever, dyspnea, and constitutional symptoms, but a wide range of clinical presentations can be seen. Nocardia can spread hematogenously to extrapulmonary locations- most frequently to the CNS with brain abscess, but also to the skin and joints [4]. Approximately one-third of infected immunocompromised patients will have disseminated disease [4]. Diagnosis is often difficult owing to the slow growth of the organism. Treatment with sulfonimides is usually effective.

X-ray:

The infection typically begins as a localized consolidation which progresses to cavitation. The consolidation can appear mass-like. Chest wall extension with rib destruction and sinus tract formation can be seen. Multiple pulmonary nodules which can cavitate (33%) are another common manifestation of infection, particularly in HIV patients [2]. Pleural effusion occurs in approximately 50% of cases and adenopathy can also be identified. However, other authors state that mediastinal and hilar adenopathy are not usual features of pulmonary nocardiosis [4].

REFERENCES:

(1) J Comput Assist Tomogr 1995; 19 (1): 52-55

(2) J Comput Assist Tomogr 1995; 19 (5): 726-732

(3) J Thorac Imaging 1998; Conces DJ. Bacterial pneumonia in immunocompromised patients. 13: 261-270

(4) AJR 2011; Kanne JP, et al. CT findings of pulmonary Nocardiosis. 197: W266-W272

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