Cystic acne, also known as noulocystic acne, is a severe form of acne wherein acne develops into small cysts. Acne cysts are not true cysts in the sense that they are not abnormal dilations of skin structure, but rather nodules of inflammation. Although not uncommon, it is rarer than other types of acne. Like other forms, it is caused by an excess buildup of sebum in the pores and, contrary to popular belief, is not caused by, nor is it affected by, hygiene or the lack thereof. A common treatment for cystic acne is Isotretinoin, which cures most acne in about 90% of patients.