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.



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