The Significance of Protein and Non-protein Tuberculin Sensitivity and Insensitivity in Sarcoidosis.

ONE of the more perplexing features of sarcoidosis is the abnormally high rate of insensitivity to tuberculin injected intradermally. In any large urban community in England very few adults between ages 30 and 65 will be found not reacting to a dose of ioo units (o.ooz mg.) of tuberculin; fewer still will be found in a comparable age-group of ambulant cases of tuberculosis, yet half or more of a group of cases of active sarcoidosis may be found to be insensitive to ioo units of Purified Protein Derivative (PPD) tuberculin. The significance of this 'anergic' state in patients showing lesions with sarcoid histology, is fundamental to understanding the immunological abnormality in this condition.