Acne Vulgaris

Definition and Characteristics

Exclusively human disorder of the pilosebaceous unit, mostly affecting the so called “sebaceous follicles” located on the face, chest, shoulders and back (seborrheic areas).

Prevalence

Initiating with the adrenarche and mostly with puberty it exhibits a peak incidence at 15–18 years of age. Neonatal and infantile acne can occur but are rare. Adolescents are reported to experience acne lesions in 70–87%, whereas acne is clinically relevant in 30%. There is a spontaneous regression after puberty, but acne persists over the age of 25 years in 10% and can last up to the fourth decade of life, and even up to the sixth decade of life in some cases. Two to 7% of the patients with acne experience a severe course associated with considerable scarring. Acne occurs in all races with a more severe course in Caucasians than in pigmented races. Japanese usually present a milder course of acne than other populations.

Genes

Identical sebum excretion rates but varying...