Post-primary pulmonary tuberculosis

A patient from Honduras presented to the emergency department with night sweats and fever for the last four days. He also had dyspnea and a productive cough since one month ago. He was additionally a former smoker from one month ago and, he had been in prison ten years ago

PA chest radiography shows multiple bilateral fibronodular opacities and ill-defined pulmonary nodules with an upper lung lobes predominance. Some cavitary lesions can also be observed.

Multiple axial CT images through the lungs demonstrate multiple thick-walled pulmonary cavities predominantly in the apical and posterior segments of the upper lobes, as well as the superior segments of the lower lobes. There are multiple areas of nodularity and partial consolidation in a bilateral and peripheric distribution, forming a tree-in-bud pattern in some locations. Apical architectural distortion, fibrotic bronchiectasis and upper lung volume loss can additionally be observed. There are also small mediastinal lymphadenopathies.

The imaging findings in this case, along with the clinical presentation, were highly suggestive of tuberculosis reactivation. The final diagnosis was made by positive PCR on the sputum for Mycobacterium tuberculosis complex.

Tuberculosis is an infectious disease mostly transmitted by Mycobacterium tuberculosis, contained in airborne droplets [1,2]. It constitutes a world health issue, causing 9 million people new infections and 1.5 million deads every year [1]. Most cases occur in developing countries, particularly in Africa and Asia [1,2]. This bacteria reaches the terminal airspaces by inhalation, where most individuals will harbour the infection and will remain asymptomatic and noncontagious. However, some people will develop active tuberculosis within the first 1-2 years, while others will be able to control the initial infection, but the microorganism will remain dormant and reactivate many years after causing post-primary tuberculosis [1,2].

Regarding the clinical aspect, tuberculosis predominantly affects the pulmonary system, although it can involve any organ system [3]. The active disease presents with multiple symptoms, including fever, night sweats, productive cough that produces bloody sputum, and weight loss [1,2].

Post-primary pulmonary tuberculosis associates patchy and poorly defined consolidations involving the apical and posterior segments of the upper lobes and the superior segments of the lower lobes (1,2,3,4). Although the presence of cavities is considered the hallmark of reactivation tuberculosis, they are isolated to 20-45% of the subjects (1,2). The cavitary lesions typically have irregular and thick walls [1]. However, the most common CT findings in this disease are centrilobular and tree-in-bud nodules distributed in the lungs periphery and both the upper and lower lobes, known to be a highly suggestive sign of active infection [1,2].

Standard treatment of active pulmonary tuberculosis consists of one first regimen of isoniazid, rifampin, pyrazinamide, and ethambutol for two months (bactericidal phase); and a second regimen of isoniazid and rifampin during four more months (sterilizing phase) [1,4]. The length of the treatment can have variations depending on the presence of cavitation on the initial chest radiograph or having a positive tuberculosis positive culture after two months of therapy initiation [1].

Tuberculosis is still a leading cause of death worldwide. The combination of the clinical history with the typical imaging findings is the clue to suspect this entity, being able to start the treatment before making a microbiological diagnosis.

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