Acne on the back is not necessarily a symptom of AIDS. If the localized skin only has pimples, it may be caused by acne, folliculitis and other diseases. 1. Acne: The onset of acne is usually related to endocrine factors, Propionibacterium acnes infection, and excessive sebaceous gland secretion, etc. It often manifests itself clinically as pimples, papules, and pustules, etc., and is commonly found on the face, chest, and back. 2. Folliculitis: Folliculitis is usually associated with bacterial infection of the hair follicles, mainly manifested as red papules or pustules, any area with hair may develop, some patients will appear back acne. If the back only appear pimples, no other abnormalities, generally does not mean that it is suffering from AIDS, it is recommended that the patient go to the regular hospital, for relevant examination, to clarify the cause.