<prompt> Pathergy test is positive in?Richters diseaseBehcets diseaseRitters diseaseErythema multiforme  <response>: ANSWER: B Behcets diseaseREF: Harrison 17th ed Table 320-1Pathergy is a cutaneous phenomenon seen with both Behcets disease and pyoderma gangrenosumIn this condition a minor trauma such as a bump or bruise leads to the development of skin lesions or ulcers that may be resistant to healing. Pathergy can also lead to ulcerations at the site of surgical Incisions.It is also important to note that, while a positive pathergy reaction helps to confirm a specific Behcets disease diagnosis, a negative reaction does not invalidate a BD diagnosis, because the disease process has to be active at the time of the skin prick test to produce a pathergy reaction.Diagnostic Criteria of Behcets DiseaseRecurrent oral ulceration plus two of the following:Recur rent genital ulcerationEye lesionsSkin lesionsPathergy test 