Acne Lesions and Classification
Acne lesions are divided into inflammatory and noninflammatory lesions. Noninflammatory lesions consist of open and closed comedones. Open and closed comedones are the first lesions to appear. Closed comedones or white heads appear as white microcysts. The follicular opening is barely perceptible. Open comedones or black heads have a dilated follicular orifice that contains a plug with a dark surface. The opening may be small or very large. Inflammatory acne lesions are characterized by the presence of papules, pustules, and nodules (cysts). Papules are less than 5 mm in diameter. Pustules have a visible central core of purulent material. Nodules are greater than 5 mm in diameter. Nodules may become suppurative or hemorrhagic. Suppurative nodular lesions have been referred to as cysts because of their resemblance to inflamed epidermal cysts. Recurring rupture and reepithelialization of cysts leads to epithelial-lined sinus tracks, often accompanied by disfiguring scars.
Inflammatory acne lesions are classified as papulopustular and/or nodular. A severity grade based on a lesion count approximation is assigned as mild, moderate, or severe. Mild cases have few to several lesions. They do not have cysts. Moderate cases have several to many papules and few to several cysts. Patients with severe acne have numerous or extensive papulopustular lesions and many cysts. Other factors in assessing severity include ongoing scarring, persistent purulent and/or serosanguineous drainage from lesions, and the presence of sinus tracks. Degree of severity is also determined by occupational disability, psychosocial impact, and the failure of response to previous treatment.