in time variation of pathergy phenomenon in behcet's disease

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.