The etiology of CD is unknown, but there are studies indicated that the occurrence of CD may be related to the infection of human herpes virus-8 (HHV-8) or human immunodeficiency virus (HIV), immune dysfunction and overproduction of interleukin-6 (IL-6).[3] Asao et al have proved IL-6 transgenic mice showed similar disorders related to CD, which suggested the contribution of IL-6 to CD.[4]. This evidence concerns the gene IL6 and infection.