Acne is a disease of the pilosebaceous unit caused by multiple factors including abnormal keratinization, increased sebum production, proliferation of P. acnes bacteria, and hormones. The primary lesions are closed and open comedones, papules, pustules, nodules, cysts, and scars. Treatment focuses on correcting keratinization, modulating the immune response, reducing sebum production, and decreasing androgenic effects to inhibit P. acnes growth. Topical therapies include retinoids, benzoyl peroxide, and azelaic acid, while systemic options include isotretinoin, hormonal contraceptives, and spironolactone.