Behçet's syndrome. Immunopathologic and histopathologic assessment of pathergy lesions is useful in diagnosis and follow-up.

Behçet's syndrome is a complex multisystem disease that, due to the absence of a pathognomonic laboratory test, must be diagnosed using clinical criteria. Clinical pathergy testing, the induction of a sterile pustule 24 hours after cutaneous trauma, has been proposed as a useful adjunct to diagnosis. We have expanded this concept by showing the usefulness of examining pathergy lesions by routine and immunofluorescence microscopy in the diagnosis of nine patients with Behçet's syndrome. Furthermore, histopathologic pathergy assessments correlated with clinical disease activity and/or response to experimental oral thalidomide therapy in five of six patients with Behçet's syndrome who were retested.