Among patients with tuberculosis in India, which is the most common site of extrapulmonary tuberculosis?

Explanation

## Epidemiology of Extrapulmonary Tuberculosis **Key Point:** Lymph node tuberculosis (TB lymphadenitis) is the most common site of extrapulmonary TB globally and in India, accounting for approximately 40–50% of all extrapulmonary TB cases. ### Distribution of Extrapulmonary TB Sites | Site | Frequency (%) | Clinical Features | |------|---------------|-------------------| | **Lymph node** | 40–50 | Painless, firm, matted nodes; most common in cervical region | | Abdominal | 15–20 | Ascites, mesenteric lymphadenitis, peritonitis | | Skeletal | 10–15 | Spine (Pott's disease), hip, knee; insidious onset | | Meningeal | 5–10 | High mortality if untreated; requires urgent diagnosis | | Pleural | 5–10 | Exudative effusion; often with primary TB | | Genitourinary | 3–5 | Often asymptomatic; detected on screening | **High-Yield:** Lymph node TB is particularly common in: - Children and young adults - Immunocompromised patients (HIV+) - Patients with primary TB complex - Urban and semi-urban settings in India **Clinical Pearl:** Cervical lymph node TB (scrofula) is the most frequent presentation of TB lymphadenitis in India. Diagnosis requires: - Fine needle aspiration cytology (FNAC) showing epithelioid granulomas - AFB smear positivity in 10–20% of cases - TB culture or GeneXpert MTB/RIF for confirmation ### Why Lymph Node TB Is Most Common 1. **Hematogenous and lymphatic spread** during primary TB complex 2. **Lower mycobacterial load** required for lymph node infection vs. CNS disease 3. **Accessibility for diagnosis** (FNAC, biopsy) → higher detection rate 4. **Age-related epidemiology:** children with primary TB frequently develop regional lymphadenopathy **Mnemonic:** **LACES** — Lymph nodes, Abdominal, CNS (meningitis), Extrapulmonary (skeletal, pleural), Sites (in order of frequency) — helps recall the hierarchy of extrapulmonary TB. [cite:Park 26e Ch 7]