Sarcoidosis and tuberculosis: Variable immunologically determined reactions to a common cause?

HAVING reviewed the records of 208 consecutive cases of sarcoidosis diagnosed in one hospital over a period of 20 years we describe the clinical course of 18 patients (9%) from whom mycobacterium tuberculosis (M.tub.) was cultured. These figures implicate the tubercle bacillus in either a primary etiological or secondary complicating role in at least some cases of sarcoidosis. We favor the former hypothesis and outline a possible mechanism involving interaction between the humoral and cellular immune systems to explain the coexistence of the two diseases, i.e., a changing reaction to an antigen common to both: the tubercle bacillus.