GRANULOMATOUS INFECTIONS - ETIOLOGY AND CLASSIFICATION

Granulomatous disorders are frequently due to a wide variety of infect ions. Over the past decade advances in molecular diagnostic techniques have allowed identification of organisms involved in granulomatous di sorders that previously were of unknown etiology. On the basis of curr ently available information, granulomatous infections can now be class ified in three categories. Group 1 infections are due to a well-recogn ized organism. Group 2 comprises infections due to organisms that have been recently identified in granulomas by molecular methods but are n ot readily isolated by conventional microbiological techniques. Group 3 consists of disorders for which the causal organisms have not yet be en identified but are strongly suspected; further advances in diagnost ic techniques will lead to reclassification of some of these disorders as group 2. This review describes the etiology, histopathologic featu res, and classification of granulomatous disorders, with an emphasis o n those of groups 2 and 3.