The Pathergy Test as a Diagnostic Tool.

The pathergy test produces a nonspecific hyperreactive lesion in Behçet's disease (BD), a finding that has been known since 1937. Pathergy refers to the development of new skin lesions or the aggravation of existing ones after trivial trauma. In clinical practice, the pathergy test induces a skin response by needleprick, with positive reactions manifesting as a papule or pustule developing by 48 hours. The pathergy test is one of the major features and diagnostic criteria of the disease. It is very similar to the erythematous papules or pustules that appear spontaneously in patients with BD. There is no standardized method for conducting the pathergy test. Intradermal, intravenous, and subcutaneous applications are used. There is no generally accepted opinion on which form of the test yields a higher positivity rate. The pathergy reaction is also reported in pyoderma gangrenosum, and has been noted in other neutrophilic dermatoses such as Sweet syndrome. The overall objective of this contribution is to provide a review of the available information, literature, and research relating to the pathergy test.