Pulmonary Nocardiosis in a Post-Tuberculosis Patient
Pulmonary nocardiosis is an uncommon but potentially life-threatening opportunistic infection caused by aerobic actinomycetes of the genus Nocardia. Owing to its nonspecific clinical and radiological manifestations, it frequently mimics pulmonary tuberculosis, bacterial pneumonia, and fungal infections, often resulting in delayed diagnosis and treatment. We report the case of a 52-year-old immunocompetent female with a history of successfully treated pulmonary tuberculosis who presented with cough with expectoration, fever, chest pain, and loss of appetite. Clinical examination revealed bilateral decreased breath sounds with occasional wheeze. Laboratory investigations demonstrated neutrophilic leukocytosis, while conventional acid-fast bacilli staining was negative. Computed tomography of the chest showed bilateral upper lobe cavitary consolidations with multiple centrilobular nodules and a tree-in-bud appearance, initially raising suspicion of recurrent pulmonary tuberculosis. However, modified acid-fast staining of sputum demonstrated thin, branching filamentous organisms consistent with Nocardia species, establishing the diagnosis of pulmonary nocardiosis. Bronchoalveolar lavage culture was negative, likely due to prior antibiotic exposure. The patient was treated with weight-adjusted double-strength trimethoprim-sulfamethoxazole, resulting in marked clinical improvement and significant radiological resolution on follow-up. This case emphasizes the importance of maintaining a high index of suspicion for pulmonary nocardiosis in patients with post-tuberculous structural lung disease who present with persistent respiratory symptoms and cavitary pulmonary lesions despite negative acid-fast bacilli results. Early microbiological confirmation using modified acid-fast staining and prompt initiation of appropriate antimicrobial therapy are crucial to prevent dissemination and improve clinical outcomes, particularly in tuberculosis-endemic regions where nocardiosis remains an underrecognized differential diagnosis.