Pathergy Summary Overview What is pathergy? Pathergy is an exaggerated skin injury occurring after minor trauma such as bump, bruise, needle stick injury. Skin trauma → Erythematous induration → Progress to papules or sterile pustules Pathergy is seen in the following: • Behcet Disease • Pyoderma gangrenosum (PG) • Sweet syndrome • Chronic myeloid leukemia (CML) treated with interferon-alpha • Atypical eosinophilic pustular folliculitis • Myeloproliferative disorders • Erythema elevatum diutinum • Blind loop syndrome • Non-Hodgkin's lymphoma What is the skin pathergy test? • Multiple pricks are made into the forearm, using a sterile needle. The pricked area is observed over the next few days. • Pathergy test is positive if you see any of the following: - Red bump (papule) - Pustule - Ulceration • Pathergy testing is only indicated in establishing the diagnosis of BD. • 97% specificity and 92% sensitivity for BD. • The test is evaluated 24 to 48 hours after initial provocation. • The positivity rate for pathergy tests in BD is highest in countries along the Silk Route, which includes the Middle East, Far East, and Mediterranean Basin. #Pathergy #diagnosis #differential #allergy #immunology #dermatology #skin
