Our results of a general pattern of lower FA and higher RD in association with cells expressing Perforin, and higher FA and lower RD in those not expressing Perforin and Granzyme, suggests that cell damage following CTLs activation may be a mechanism involved in disrupting WM microstructure in BD, with effects distributing along the gradient of toxins expression (Fig. 3). This evidence concerns the gene PRF1 and Behcet disease.