Evaluation of pathergy test positivity in familial Mediterranean fever patients and comparison of clinical manifestations of FMF with Behçet's disease.

Familial Mediterranean fever (FMF) shares a number of features with Behçet's disease (BD), such as their common ethnic origin, etiopathogenetic mechanisms, symptoms, and treatment. Pathergy reaction is accepted as a major criterion in BD. We aimed to determine the frequency of pathergy positivity in FMF patients and compared clinical features between FMF and BD. Pathergy test was performed in patients with FMF, BD, and healthy controls. Diagnostic criteria for FMF and BD were screened in both groups. None of the FMF patients or healthy controls yielded positive pathergy test. Pathergy test was positive in 13 out of 31 (41.9%) of the patients with BD. None of the FMF patients fulfilled the International Study Group criteria for BD. None of the BD patients fulfilled the Livneh diagnostic criteria for FMF. BD and FMF are associated with neutrophilic dermatoses and neutrophil hyper-reactivity. Although pathergy test and erysipelas-like erythema share some histological findings, pathergy test was negative among FMF patients.