19, 20 However, the results have been inconsistent in dermatological diseases; for instance, in cases of psoriasis, their participation or lack of influence has been reported21. A similar condition has been observed in Alopecia Areata (AA), where a previous association study proposed the involvement of CTLA4 polymorphisms as a risk factor in its development in a European population;22 however, another study revealed that these polymorphisms were irrelevant for the development of AA in a Mexican population.9 This evidence concerns the gene CTLA4 and psoriasis.