Sarcoidosis and tuberculosis: the same disease with different manifestations or similar manifestations of different...

Ever since sarcoidosis was first described, its relationship with tuberculosis has been debated. Whereas some consider sarcoidosis and tuberculosis as two extremes of the same disease process, other researchers have negated the role of mycobacteria in causation of sarcoidosis. Whether or not linked causally, there are obvious clinical similarities that make differential diagnosis of the two conditions very challenging, particularly in countries with high burden of tuberculosis. Herein we analyze the relationship between sarcoidosis and tuberculosis and its implications in clinical practice.

Initial studies had focused on finding an epidemiological link between the two conditions or demonstration of mycobacteria in sarcoid lesions on histology. Results from these studies were at best suggestive. Recent molecular and immunological studies suggest mycobacterial antigens are the inciting agents in a proportion of sarcoidosis patients. Evidence is stronger from countries with high burden of tuberculosis. Tuberculosis can manifest as a complication of treatment in sarcoidosis and the two conditions can rarely co-exist.

The balance of evidence favors mycobacteria or their products as a trigger for inciting immune responses leading to sarcoidosis in a proportion of patients, which is likely to be higher in countries with high tuberculosis burden. This evidence also highlights the limitations of molecular or serological studies to discriminate between the two conditions.