TB or Not TB: Lung Nocardiosis, a Tuberculosis Mimicker

Abstract

Nocardia, a gram-positive bacterium found in soil and water, rarely causes infections in immunocompetent patients. Diagnosing and treating nocardiosis can be challenging due to its infrequency and the similarity of its symptoms to other diseases. We describe the case of a middle-aged male with a history of latent tuberculosis who presented with hemoptysis. Imaging revealed a persistent lung mass, and pathology and microbiology studies confirmed Nocardia infection. The patient was treated with antibiotics and discharged home. Pulmonary nocardiosis can mimic tuberculosis, fungal infections, or malignancies. Immunocompetent patients make up one-third of the cases. Diagnosis can be difficult, as the organism takes time to grow in culture, but molecular techniques and histology can aid in diagnosis. Treatment often involves a six- to 12-month course of trimethoprim-sulfamethoxazole (TMP-SMX). Prompt identification of the etiological agent is essential for effective treatment, especially for immunocompetent patients who may not exhibit typical risk factors.

Keywords: lung nocardiosis; necrotizing pneumonia; nocardia in immunocompetent; nocardia species; pulmonary cavitation.

Figure 1. Computed tomography of the chest in coronal (A) and axial (B) views.

It shows a left upper lobe mass (red arrow) which measures up to 6.7 cm in diameter. It contains a fluid density material and heterogeneously enhances.

Figure 2. Chest X-ray in the anteroposterior view done on the day of current admission.

There is a large mass in the left upper lung, which appears to have progressed slightly. The right lung is clear. There is no evidence of pneumothorax or pleural effusion. Also, it shows a remote left clavicular fracture.

Figure 3. Computed tomography of the chest in coronal (A) and axial (B) views performed in current admission.

It shows the same upper lung mass, which increased in size (red arrow). The mass currently measures 7.7 cm with a mild patchy infiltrate seen around the mass.

Figure 4. Pathology of the resected cavitary lesion in the left upper lobe.

Picture A includes a macroscopic pathologic sample consisting of a lobectomy measuring 16x8x6.5 cm. There is a mass measuring 11 cm (red arrow) located near the pleura of the lung. This mass is located 3 cm from the bronchial margin. Dissection of the mass reveals a cavitary lung lesion filled with degenerative yellow-tan debris. Pictures B, C, and D correspond to low-, medium-, and high-power fields in the microscope of the mass. These show acute necrotizing cavitary granulomatous inflammation with chronic bronchitis.

Figure 5. Microscopic view of the patient's tissue culture findings.