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A 30-year-old farmer presented to the hospital with multiple swelling in the neck for the past 1 year. He doesn’t have any other systemic symptoms. He has visited many small hospitals and was referred to a larger hospital to rule out cancer of the lymph nodes. Lymph node biopsy was done to rule out cancer, it was also sent for CBNAAT, a rapid molecular test to detect the bacteria causing tuberculosis (TB) as well as for Mycobacteriology culture. Biopsy was negative for cancer, CBNAAT was negative, while mycobacteriology culture of the tissue showed the growth of Mycobacterium tuberculosis, the bacteria that causes the chronic infection TB.
Extrapulmonary Tuberculosis (EPTB) refers to TB infection occurring outside the lungs. While pulmonary TB, the more common form of TB, primarily affects the lungs, EPTB can involve other organs such as lymph nodes, pleura, bones, joints, genitourinary tract, peritoneal organs, meninges and the central nervous system. Unlike pulmonary TB, EPTB is not contagious as the TB bacillus is retained inside the body in the different internal organs, unless there is an open abscess or lesion with a high concentration of TB bacteria and extensive drainage fluid that is discharged into the air. The prevalence of EPTB varies by geographic region, socioeconomic conditions, and HIV prevalence. According to the World Health Organisation (WHO) globally, about 15% of TB cases are extrapulmonary1. However, in regions with high HIV prevalence, EPTB rates can be significantly higher due to the immune system’s impairment in HIV-positive individuals.
EPTB can mimic many other diseases due to its wide range of manifestations.2 Symptoms are often non-specific and vary greatly depending on the affected organ. For example, the most common form of EPTB is TB of the lymph nodes which presents as swollen lymph nodes, often mistaken for other infections or cancer; Skeletal TB or bone TB may cause back pain or joint symptoms, which can be confused with other musculoskeletal disorders, on the other hand genitourinary TB can lead to urinary symptoms or reproductive issues, potentially being misdiagnosed as other urological or gynaecological conditions.
The rarity and atypical presentations of EPTB can often lead to misdiagnosis or delayed diagnosis. Clinicians may not initially consider TB in differential diagnoses, leading to further diagnostic delays. Especially in areas with low TB incidence, healthcare providers might not immediately consider TB in the differential diagnosis of non-pulmonary symptoms, leading to under-recognition and delayed treatment. On the other hand, in HIV-infected patients, EPTB can be more severe and atypical, complicating diagnosis due to overlapping symptoms with opportunistic infections.
However, there still remains a critical need for EPTB diagnostic assays that are non-invasive, rapid, accurate, affordable and fit for point of care. Laboratory diagnosis of EPTB often relies on mycobacterial cultures, which can be slow and have variable sensitivity depending on the specimen type and site. Cultures from non-pulmonary sites may take longer to yield results. For example, an average duration of 2-3 weeks is needed for a culture positive result. While histological examination of biopsied tissues can reveal caseating granulomas indicative of TB, the specificity is not absolute. Granulomas can also be seen in other conditions, leading to potential diagnostic ambiguity. Recent advances in molecular diagnostic methods – for example Cartridge based nucleic acid amplification test (CBNAAT) can detect Mycobacterium tuberculosis DNA but may not always be available in all settings and can have variable sensitivity based on the sample type and quality of TB bacteria in the sample.4
An important feature of EPTB is that there is low bacterial load in the extrapulmonary sites compared to pulmonary TB that can yield false-negative results in traditional diagnostic tests. Therefore, clinicians need to have a high index of suspicion and will have to use multiple diagnostic modalities to establish EPTB.
The future for early and accurate diagnosis of EPTB depends on developing sensitive and specific assays for detecting TB-related biomarkers from non-invasive, easy-to-obtain samples like urine or stool.
In conclusion, in a country where tuberculosis is endemic and increased efforts are made by national tuberculosis programs to control pulmonary tuberculosis, doctors and patients need to have increased awareness of extrapulmonary tuberculosis which can cause increased disability and death rate if not diagnosed early and accurately. Faster and more accurate diagnosis as well as more effective drugs are desperately needed to control the rise in EPTB not only in India but also globally.
Dr. Joy Sarojini Michael is a Clinical Microbiologist working in the field of Mycobacteriology, Mycology and Infection control for over 23 years. In the field of Mycobacteriology she has experience in diagnostics and research in the fields of evaluation of new TB diagnostics in both adults and children for pulmonary as well as extrapulmonary TB, molecular epidemiology of mycobacterial infections including DR-TB, Zoonotic TB and non-tuberculosis mycobacteria. She has worked at different capacities with RNTCP/NTEP and Central TB Division both at the Tamil Nadu State and National Level.
India Health Fund is registered as Confluence for Health Action and Transformation Foundation (CHATF), a Section 8
charitable company incorporated in India, supported by the Tata Trusts.
