# Pulmonary Tuberculosis Clinical Features and Radiology > Pulmonary tuberculosis clinical features and radiology for NEET-PG Medicine: primary versus post-primary disease, Ghon complex and cavitation. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/pulmonary-tuberculosis-clinical-features-and-radiology - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Harrison's Principles of Internal Medicine; Davidson's Principles and Practice of Medicine; National Tuberculosis Elimination Programme Guidelines - How to cite: "Pulmonary Tuberculosis Clinical Features and Radiology", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/pulmonary-tuberculosis-clinical-features-and-radiology ## Direct answer Pulmonary tuberculosis is a Mycobacterium tuberculosis infection of the lung, either primary, seen in children and non-immune contacts, or post-primary, arising in adults when a latent focus reactivates. Radiology separates the two: primary disease shows a Ghon complex, a focus with a draining hilar node, while post-primary disease favours upper lobe apical and posterior consolidation, cavitation and fibrosis. Microscopy, culture or molecular testing confirms the diagnosis, with radiology supporting it. ## What you must remember - **Ghon complex:** a subpleural caseating focus with a draining hilar or mediastinal node, which usually heals and calcifies; the healed lesion is called a Ranke complex. - **Simon focus:** an apical lesion seeded during the initial bacteraemia, which reactivates decades later and underlies most post-primary cavities. - **Primary disease:** middle and lower zone consolidation with hilar lymphadenopathy, common in children and HIV-positive patients, and sometimes with pleural effusion. - **Post-primary disease:** upper lobe apical and posterior segment involvement, with cavitation, fibrosis and tree-in-bud nodules from bronchogenic spread. - **Cavitary pattern:** a thick-walled cavity with surrounding consolidation and satellite lesions signals high bacillary load and infectivity. - **Miliary pattern:** innumerable 1 to 3 millimetre nodules from haematogenous dissemination, which can be missed on early plain films. - **Diagnosis:** CBNAAT, the molecular test used first-line under the National Tuberculosis Elimination Programme, detects both Mycobacterium tuberculosis and rifampicin resistance. ## Reading a film in a young labourer and a child A 28-year-old construction worker has six weeks of evening fever, night sweats, weight loss and productive cough. His chest film shows right upper lobe consolidation with a thick-walled cavity and satellite nodules. 1. **Confirm the bacteriology:** Sputum CBNAAT is positive and sensitive to rifampicin, smear is 2-plus, and HIV testing is negative. 2. **Name the pattern:** The diagnosis is post-primary pulmonary tuberculosis with infectious cavitary disease, because a cavity with satellite lesions signals high bacillary load and infectivity. 3. **Contrast the child:** A 5-year-old household contact of the same family has a fortnight of fever and a right hilar node with lower zone consolidation on film. 4. **Name the primary pattern:** The child shows a primary pattern, and the diagnosis rests on the contact history, tuberculin or interferon-gamma testing and clinical features rather than sputum, which is seldom available in children. 5. **Use location, not symptoms:** Lesion location, not symptoms alone, distinguishes primary from post-primary disease. 6. **Screen the household:** Because the adult's smear is positive, screening of household contacts is urgent, and the child is evaluated for primary infection rather than dismissed as an unrelated fever. ## Where radiology and tests mislead The same few confusions recur with radiology and testing. - **Trap:** assuming all tuberculosis is apical. — **Correct:** lower and middle zones are common in HIV-positive patients and children, and the classic apical picture is a clue for immunocompetent adults. - **Trap:** confusing the Ghon complex with the Simon focus. — **Correct:** the Ghon complex is the primary lesion with its node, whereas the Simon focus is the apical site of later reactivation. - **Trap:** trusting a normal chest film or a negative smear in HIV. — **Correct:** neither excludes tuberculosis in HIV, so molecular testing or culture is needed. - **Trap:** assuming a febrile patient with a nodular pattern has pneumonia. — **Correct:** in an Indian context miliary tuberculosis often presents with fever and pancytopenia, so the nodular pattern should be recognised. ## Frequently asked questions ### What is a Ghon complex? A Ghon complex is the primary tuberculosis lesion, a subpleural focus of caseating granuloma together with a draining hilar or mediastinal lymph node. It often heals and calcifies, and the healed complex is called a Ranke complex. ### Where are cavities typically seen in post-primary pulmonary tuberculosis? Cavities in post-primary pulmonary tuberculosis favour the apical and posterior segments of the upper lobes, reflecting reactivation of the Simon focus. Thick-walled cavities with satellite lesions indicate a high bacillary load and marked infectivity. ### Which radiological pattern suggests miliary tuberculosis? Miliary tuberculosis shows innumerable 1 to 3 millimetre nodules spread uniformly through both lungs, reflecting haematogenous dissemination. The pattern can be missed on a plain film in early disease, so high-resolution CT is useful when suspicion is high. ### Why can primary tuberculosis appear in the lower lobes? Primary tuberculosis in children and non-immune adults commonly involves the middle and lower zones, which receive more ventilation and therefore more inhaled bacilli. Hilar lymphadenopathy with lower zone consolidation is the classic primary pattern.