Rare Extrapulmonary Tuberculosis: Covert symptoms and Diagnostic Dilemma.

Background: Pulmonary tuberculosis may result in haematogenous and lymphatic extension in case of failure of early detection, or immunocompromised status, leading to extrapulmonary tuberculosis. Rare sites of extrapulmonary tuberculosis include the gastrointestinal tract, musculoskeletal system, genital tract, middle ear and pericardium. Histopathological findings of macro-confluent granuloma with or without caseous necrosis, along with detection of acid-fast bacilli (AFB) on Ziehl-Neelsen (ZN) staining, and GeneXpert for detection of Mycobacterium tuberculosis DNA, are key in establishing a diagnosis of tuberculosis.

Methodology: Biopsy-proven extrapulmonary granulomatous lesions were included in this study. Histopathological evaluation of all extrapulmonary biopsy specimens sent to the Department of Pathology were done for the presence of granuloma and necrosis, and ZN staining for AFB was done in all the cases of granulomatous lesions with or without the presence of necrosis. The same cases, with biopsy specimens sent in normal saline, were re-evaluated in a molecular laboratory with the help of GeneXpert MTB to detect the DNA of Mycobacterium tuberculosis. All biopsy specimens from extrapulmonary sites which were sent to the Department of Pathology were used for DNA extraction.

Results: Out of the 10 cases of extrapulmonary granulomatous lesions, 8 showed caseous necrosis on microscopy, and 7 showed the presence of acid-fast bacilli on Ziehl-Neelsen staining. GeneXpert detected DNA of Mycobacterium tuberculosis in 9 cases.

Conclusion: Extrapulmonary tuberculosis rarely occurs as primary, and mostly spreads from lung parenchyma via a haematogenous route. Tuberculosis of the gastrointestinal tract, peritoneum, lymph nodes, and solid viscera are together termed abdominal tuberculosis. Entities like tuberculosis of the pericardium and ear are extremely rare. Extrapulmonary tuberculosis should be a differential in cases of chronic non-responding cases with diagnostic dilemmas. To avoid diagnostic delay, in cases of high suspicion, one should go for biopsy along with ZN staining for diagnostic confirmation as this is cost-effective, followed by GeneXpert for Mycobacterium tuberculosis in highly suspected cases with absent caseous necrosis and negative ZN staining.