Typical features of acne include seborrhea (increased oil secretion), microcomedones, comedones, papules, pustules, nodules (large papules), and possibly scarring. The appearance of acne varies with skin color. It may result in psychological and social problems.
Some of the large nodules were previously called cysts and the term nodulocystic has been used to describe severe cases of inflammatory acne.
Acne scars are the result of inflammation within the dermal layer of skin brought on by acne and are estimated to affect 95% of people with acne vulgaris. The scar is created by an abnormal form of healing following this dermal inflammation. Scarring is most likely to occur with severe nodulocystic acne, but may occur with any form of acne vulgaris. Acne scars are classified based on whether the abnormal healing response following dermal inflammation leads to excess collagen deposition or collagen loss at the site of the acne lesion.
Atrophic acne scars are the most common type of acne scar and have lost collagen from this healing response. Atrophic scars may be further classified as ice-pick scars, boxcar scars, and rolling scars. Ice pick scars are typically described as narrow (less than 2 mm across), deep scars that extend into the dermis. Rolling scars are wider than ice pick scars (4–5 mm across) and have a wave-like pattern of depth in the skin. Boxcar scars are round or ovoid indented scars with sharp borders and vary in size from 1.5–4 mm across.
Hypertrophic scars are less common and are characterized by increased collagen content after the abnormal healing response. They are described as firm and raised from the skin. Hypertrophic scars remain within the original margins of the wound whereas keloid scars can form scar tissue outside of these borders. Keloid scars from acne usually occur in men and on the trunk of the body rather than the face.