Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 34 3-4 1996 12 15 70 72 C. Chams F. Davatchi F. Shahram M. Akbarian F. Gharibdoost A. Nadji. A.R. Jamshidi 2015 09 28 The pathergy phenomenon (PP) is one of the hallmarks of Behcet's Disease (BD). It has been reported to be positive from 17.5% to 83% of cases in different studies. PP is used as a diagnosis criterion in the Dilsen criteria, the Japan criteria, the International criteria, and the Iran criteria. It is therefore important to know wether PP is a fix manifestation of the disease or a cyclic manifestation like mucocutaneous disorders. To evaluate the charaterist'tc of P'P over a period of time, 77 patients were selected randomly (rcgaardless of their disease activity or their disease manifestations), to have a second pathergy test, lite pathcrgy test was performed by needle puncture on the skin of the forearm. Three methods were used: 1- needle prick with a 21 - gauge needle. 2- needle prick with a 25  gauge needle. 3- needle prick with a 25-guage needle and the injection of I drop of a sterile normal saline solution. Tlie result was evaluated 24 hours Liter. Tlie shortest interval between two tests-was one month and the longest 13 years. Die mean interval was 35.4 months, the standard deviation was 36.6 Tlurty-nine patients had a negative PI' at their first evaluation. At the second evaluation, 27 remained negative while 12 changed to positive. Thirty-eight patients had a positive PP at their first evaluation. At the second evaluation, 19 remained positive while 19 changed to negative. Although there is a difference between the two groups, it is not statistically significant (x=3.813 , p=0.05). Our data demonstrates that the pathergy phenomenon is waxing and waning, like the majority of other manifestations of Behcet's Disease. TJierefore, it may be repeated for diagnosis purposes. https://acta.tums.ac.ir/index.php/acta/article/view/1697 https://acta.tums.ac.ir/index.php/acta/article/download/1697/1690