More recently it was demonstrated that pyrin truncation in mice did not show an overt phenotype of FMF, however, pyrin-deficient and FMF-associated B30.2 mutations “knock in” mice showed severe spontaneous inflammatory phenotype, suggesting that FMF may be caused by a gain of function by disease-associated missense changes in pyrin and that FMF may not be a pure autosomal recessive disease due to the loss of protein function [21]. This evidence concerns the gene MEFV and familial Mediterranean fever.