Granuloma annulare and sarcoidosis.

Granuloma annulare (GA) and sarcoidosis are two diseases of unknown cause which involve the skin and whose basic pathology is a mononuclear histiocytic cellular reaction. Biopsy plays the major role in the diagnosis of both diseases, and no other routine laboratory test for either disease is currently available. Sarcoidosis is generally considered to be an allergic or immune granuloma with inconstant defects in cell-mediated immunity (Broom & MacLaurin, 1973). There have been no immunological studies of GA. We recently studied 14 cases and found circulating lymphokines (macrophage migration inhibition factor) in 11 which correlated with circulating macrophage migration inhibition factor in sarcoidosis (9 of 10 cases) (Umbert, Belcher & Winkelmann, 1976). The co-existence of GA and sarcoidosis in 5 patients suggests to us that there are very similar immunological reactions as well as pathology in both diseases and that the elucidation of the pathogenesis of one disease should aid in understanding the other. To our knowledge, there are no prior reports of systemic sarcoidosis coexisting with or manifesting the histological picture of GA. In this report we have demonstrated by clinical and histological criteria that GA and sarcoidosis can co-exist.