Unusual presentation of tuberculosis in an infliximab-treated patient--which is the correct TB screening before starting a biologic?

Infliximab is an anti-TNFalpha chimeric monoclonal antibody, commonly used in the treatment of moderate to severe psoriasis. TNFalpha is a pro-inflammatory cytokine which play a key role in host defense from infections by intracellular bacteria, such as Listeria monocytogenes, Histoplasma Capsulatum and especially Mycobacterium Tuberculosis. Infliximab therapy increases the risk of tuberculosis due mainly to the reactivation of latent TB infection (LTBI) and, therefore, it is mandatory to screen patients for LTBI prior to starting a treatment with anti-TNFalpha agents. We report the case of a psoriatic patient, who, despite a negative screening for infection by M. tuberculosis including both tuberculin skin test (TST) and chest X-ray, developed after 4 months of infliximab treatment, a severe pulmonary, lymphnodal and intestinal tuberculosis during infliximab treatment.