Secondary Pulmonary Tuberculosis

Secondary pulmonary tuberculosis is type III pulmonary TB, encompassing infiltrative pulmonary tuberculosis and chronic fibro-cavitary pulmonary tuberculosis from the 1978 five-type classification. It is mainly caused by reactivation of latent foci from primary infection (usually in childhood), or by exogenous reinfection. Advances in molecular biology, especially DNA fingerprinting, have provided direct evidence for exogenous reinfection. This type can occur at any age after primary infection and is most common in adults, being the most common form of adult pulmonary TB. Because the host has developed some immunity, lesions are usually localized and slowly progressive, with less systemic dissemination. Pathologically and radiologically, secondary TB is divided into exudative, proliferative, fibro-caseous, caseous pneumonia, cavitary, tuberculoma, and chronic fibro-cavitary types; lesions are rarely single and usually coexist in mixed forms, with one predominant. With modern potent chemotherapy, pathological/radiological distinction has limited treatment value but still aids differential diagnosis. Secondary TB readily forms caseous necrosis and cavities, has more sputum-positive patients, and is epidemiologically more important.

Common Symptoms

Fever of unknown origin; chest pain; hemoptysis with chest pain; menstrual changes; sputum production; hemoptysis; cough; night sweats; fatigue; weight loss

Causes and Pathogenesis

1. Endogenous reactivation: The main cause of secondary TB. Latent foci form after early bacteremia; when resistance declines, latent foci reactivate. 2. Exogenous reinfection: New infection rather than reactivation of old foci. Pathophysiology: Lesions induced by tubercle bacilli are specific, varying with host status, allergic reaction intensity, local tissue characteristics, and bacterial virulence. TB is a chronic inflammation with exudative, proliferative, and degenerative basic changes. Exudative lesions indicate high bacterial load, strong virulence, strong allergy, or acute phase; vascular permeability increases with inflammatory cells and protein extravasation, showing lymphocyte nodules and detectable tubercle bacilli.

Treatment

Drug therapy, symptomatic treatment, supportive therapy

Preventive Measures

1. Control the source of infection: Promptly detect and treat sputum-positive pulmonary TB. 2. Cut transmission routes: Ventilate rooms and disinfect. 3. Protect susceptible populations: BCG vaccination, exercise, and build resistance. Close contacts of sputum-positive patients with strongly positive PPD may receive chemoprophylaxis.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.