Paradoxical reaction in peripheral lymph node tuberculosis: a review for its prevalence, clinical characteristics, and possible treatment.

The paradoxical reaction (PR) is a transient worsening following tuberculosis treatment and it is not uncommon in lymph node tuberculosis (LNTB). PR in LNTB maybe  wrongly considered as treatment failure or relapse. This review was undertaken to address various aspects of PR associated with lymph node tuberculosis prevalence, underlying mechanism, clinical pattern, predictors, and possible treatment in an immunocompetent individual. A literature review was performed using various databases (PubMed, Scopus, Science Direct, and Google Scholar) to identify relevant articles for review. The prevalence of paradoxical reactions associated with LNTB varies from as low as 13.3% to as high as 35.3%  PR may occur during antitubercular treatment or be reported even after completion of treatment called post-therapy PR. An onset of PR may occur within a month of therapy to even 12 months from the initiation of an anti-tubercular drug. Delayed hypersensitivity reaction and reduction in immune suppression is believed to be possible mechanism leading to a paradoxical reaction. PR in LNTB is characterized by either progression of pre-existing nodal enlargement or formation of abscess, sinus formation, or appearance of new nodal enlargement or rarely extra-nodal involvement. PR is a diagnosis of exclusion and may show granuloma, positive AFB smear, or positive GeneXpert but AFB culture is always negative. Younger age, lymph node size of equal to or more than 3 cm, female gender, unilateral lymphadenopathy, and those with positive AFB on initial examination are predictors for PR in peripheral LNTB. The majority of PR in LNTB have a mild course and are generally self-limited.