CMTM2 was found to be expressed at significantly lower level in Sézary syndrome (Sz), an aggressive type of cutaneous T‐cell lymphoma, than in benign T‐cell samples, and hypermethylation of CMTM2 promoter can distinguish Sz from erythroderma secondary to inflammatory skin diseases [44]. This evidence concerns the gene CMTM2 and exfoliative dermatitis.