What are the common causes of granulomatous lymphadenitis in South East Asia?

Causes of Granulomatous Lymphadenitis in South East Asia

Tuberculosis is the predominant cause of granulomatous lymphadenitis in South East Asia, where it remains endemic and accounts for the majority of cases, particularly affecting younger populations and those from lower socioeconomic backgrounds. 1, 2

Primary Infectious Causes

Tuberculosis (Most Common)

• Mycobacterium tuberculosis is the leading cause of granulomatous lymphadenitis throughout South East Asia, where TB remains highly endemic 1, 3
• Tuberculous lymphadenitis occurs predominantly in South-East Asians, with cervical lymph nodes being the most commonly affected site 2
• The South East Asia Region accounts for 39% of the global TB burden, with approximately 3.4 million new cases annually occurring primarily in India, Bangladesh, Indonesia, Myanmar, and Thailand 3
• Extrapulmonary TB represents a significant proportion of cases, with lymph node involvement being one of the most common extrapulmonary manifestations 2
• Drug-resistant M. tuberculosis is particularly concerning in South-East Asian patients, requiring culture and sensitivity testing 2

Other Mycobacterial Infections

• Mycobacterium bovis can cause granulomatous lymphadenitis through consumption of unpasteurized milk or milk products, accounting for up to 10% of human tuberculosis in some developing countries in the region 3
• Atypical mycobacteria (M. avium, M. africanum) are rare causes but should be considered when standard TB treatment fails 3

Non-Infectious Causes

Sarcoidosis and Sarcoid-Like Reactions

• While less common than TB in South East Asia, sarcoidosis can present with granulomatous lymphadenitis and must be differentiated from TB 4, 5
• Sarcoid-like granulomas may occur as reactions to various stimuli 4

Malignancy-Associated Granulomas

• Hodgkin's lymphoma and non-Hodgkin's lymphoma can present with granulomatous changes in lymph nodes 5
• These represent important differential diagnoses that require histological confirmation to distinguish from infectious causes 5

Autoimmune Conditions

• Adult-onset Still's disease can rarely present with noncaseating suppurative granulomatous lymphadenitis, though this is extremely rare in Asian populations 6
• This diagnosis requires systematic exclusion of TB and other infectious causes, which is particularly challenging in TB-endemic regions 6

Critical Diagnostic Considerations

High-Risk Populations

• Immunocompromised patients, including those with HIV co-infection, diabetes mellitus, or receiving chemotherapy, have significantly increased risk of TB reactivation 1, 3
• Children with acute lymphoblastic leukemia have 10-22 times higher incidence of TB, with 50% showing reactivation within 5 months of completing remission induction 1
• Patients with chronic hepatitis B (prevalence 8-20% in South East Asia) require careful monitoring during immunosuppressive therapy 1

Diagnostic Approach in TB-Endemic Regions

• Routine Mantoux testing and chest X-ray are recommended for all patients presenting with lymphadenopathy in endemic areas 1
• A positive Mantoux test (induration >20mm) requires investigation with early morning gastric aspirate or induced sputum for 3 consecutive days to identify acid-fast bacilli 1
• Culture and sensitivity testing for multi-drug resistant M. tuberculosis is essential before initiating treatment 1
• Histopathological examination showing caseating granulomas strongly suggests TB, while noncaseating granulomas require broader differential consideration 6, 4

Common Pitfalls

• Do not assume all granulomatous lymphadenitis is TB despite high regional prevalence; systematic exclusion of malignancy and other causes is mandatory 6
• Failed response to complete anti-tuberculosis regimen should prompt reconsideration of alternative diagnoses rather than assuming drug resistance alone 6
• Family members must be screened and treated for TB when index case is confirmed 1
• Latent TB may reactivate during immunosuppressive therapy; prophylactic rifampin for at least 6 months is commonly practiced even without definite infection focus 1

Geographic and Social Risk Factors

• Poor housing, overcrowding, malnutrition, and lack of education contribute significantly to TB transmission in South East Asia 3
• High temperatures and humidity favor bacterial growth, increasing the burden of infectious diseases including TB 3
• Approximately 10% of total TB occurs in children, with childhood deaths usually from tuberculous meningitis or disseminated disease 3