A 63-year-old male patient presented to the outpatient department with history of low-grade fever, cough and mild dyspnoea for one week. Diagnosed case of dermatomyositis on immunosuppressants for a few months.
Chest radiograph: A region of wedge-shaped consolidation with internal cystic lucencies in left upper zone. Also patchy consolidation noted in left retrocardiac region and mild peribronchial thickening in left lower zone.
HRCT (high resolution computed tomography) chest: A (5.1 x 3.4 x 4.5 cm) relatively well-defined mass-like consolidation with internal ill-defined small cavities and an ill-defined halo of ground glass opacity noted in the subpleural aspect of anterior segment of left upper lobe. Focal mass-like consolidation and ill-defined consolidation with adjacent ground glass opacities and fine interstitial septal thickening in the posterior basal segments of bilateral lower lobes. No lymphadenopathy.
BACKGROUND: Pulmonary involvement is the most common manifestation of nocardiosis . It is caused by Nocardia species which is a gram positive, weakly acid-fast positive bacteria found in soil . It is an uncommon opportunistic infection commonly occurring in immunocompromised subjects like HIV/AIDS, organ transplant, steroid therapy and uncommonly in immunocompetent subjects as well .
CLINICAL PERSPECTIVE: Clinical features are non-specific, which ranges from acute pulmonary disease to disseminated disease course . Common pulmonary symptoms include cough, dyspnoea, chest pain, fever etc. Complications like empyema, chest wall extension of the pulmonary disease are uncommon. Imaging (chest radiograph, HRCT chest) is advocated in cases where the symptoms are not amenable to resolution by the empirical antibiotic therapy and worsening clinical picture.
IMAGING PERSPECTIVE: Usually chest radiography is the first modality offered, whereas high resolution CT (HRCT) chest is performed later on when the radiographic findings are progressing and clinical picture is not improving. Radiological findings in pulmonary nocardiosis are usually non-specific, which include nodules, consolidation, cavitation, septal thickening, ground glass opacity, crazy paving etc. . Cavitation is usually observed in immunocompromised cases. Usually there is no lymphadenopathy. Thus microbiological analysis is imperative for confirmation of Nocardia infection using samples like sputum, bronchoalveolar lavage (BAL) to isolate the microorganism .
OUTCOME: Usually medical management is done with antibiotics like sulfonamides, cotrimoxazole. This may be complemented by the temporary cessation of the immunosuppressive therapy. However surgical intervention is needed for drainage of empyema, chest wall abscess. Prognosis depends on the immune status of the patient, extent of systemic involvement with disseminated infections carrying poor prognosis, effectiveness of antibiotic treatment . Improvement in the imaging findings on follow up is usually resonated in the clinical status of the patient suggesting adequate treatment.
TAKE HOME MESSAGE:
- Pulmonary Nocardiosis is a rare manifestation and should always be considered as one of the differential diagnoses in cases of immunocompromised subjects presenting with respiratory complaints.
- Imaging is usually non-specific, therefore microbiological analysis is most important.
Differential Diagnosis List