Are We Over-Diagnosing Tuberculosis? IgG4-Related Disease is Another “Great Imitator”: A Review

Tuberculosis (TB) has a notorious role as the “great imitator”–frequently mimicking a variety of infectious and non-infectious medical conditions- which often contributes to delays in care-seeking, diagnosis, and management. Probably, the vice versa also holds true. India, being a high endemic zone for tuberculosis, the threshold to label an unexplained illness of more than 2 weeks as TB by Indian clinicians is quite low, often leading to missed or delayed diagnosis of the underlying disease. Immunoglobulin G4-related disease (IgG4-RD) is another such “mimicker” often underdiagnosed due to its varied clinical presentation and is erroneously treated with anti-tubercular drugs. The overlapping biochemical and imaging features of IgG4-RD make prospective diagnosis difficult without a high index of suspicion. The incidence reported in literature is 0.78 to 1.39 per 100,000 person-years, which is likely an underestimation of the disease. Here, we present two cases where patients suffering from IgG4-RD were initially diagnosed and treated as tuberculosis and we review the literature associated with IgG4-RD.