Sarcoidosis

Abstract

Sarcoidosis was originally recognized as a cutaneous disease producing a wide variety of clinical manifestations including macules, papules, nodules, plaques, and tumors. Pathologically, these lesions represent collections of noncaseating granulomas in the dermis and subcutaneous tissues which tend to spare the epidermis. Eventually, it was recognized that the disorder in many ways resembles tuberculosis. It tends to affect the lungs as well as the hilar and mediastinal lymph nodes. Both diseases provoke a granulomatus response, although that for tuberculosis is more intense. The similarity between these two conditions led to frequent skin testing with tuberculin and the finding that a surprisingly large number of sarcoidosis patients were tuberculin negative. Since sarcoidosis was thought by many to be an unusual form of tuberculosis, the associated anergy led to speculation that affected patients had an immunological defect which prevented their response to tuberculin. Subsequent studies have shown that sarcoidosis does produce dysfunction of both the humoral and cell-dependent immune systems. These changes appear to be secondary manifestations and contribute very little to the clinical course of the disease. The only immunological response that is specific to sarcoidosis is the very delayed response to disrupted sarcoidosis tissue administered in the Kveim test. In this chapter, we will review what is currently known about the broad, nonspecific changes in immune function that occur in sarcoidosis. Attention will then be given to the Kveim test, its sensitivity, specificity, characterization, and clinical utility.