The depth and degree of inflammation determines the amount, type and depth of scarring in acne. Acne lesions are unusual because the inflammation is initiated beneath the epidermis in the infrainfundibular region of the pilosebaceous structure.
The enzymatic activity and inflammatory mediators destroy the dermal structures, hence scarring involves the deeper structures first. Contraction leads to an atrophic scar. Acne scars are classified into various types, depending on the color, depth, contour and surface texture (Fig. 1).
In macular scars, the inflammation involves only the superficial
dermis and epidermis and gives rise to a persistent change in color.
Early scars appear erythematous, whereas older scars appear
hyperpigmented due to postinflammatory hyperpigmentation.
The inflammatory mediators stimulate melanogenesis and these scars can be persistent, particularly in darker skin individuals.
In
ice pick scars, severe inflammation of the dermis can lead to total
necrosis of the follicle with sloughing of the follicle, producing a
focal ice pick scar. Ice pick scars are narrow, punctiform, and deep.
They are so named because these scars appear as if the skin has been
pierced by an ice pick (Fig. 2).
They are sharply marginated epithelial tracts that extend vertically into the deep dermis or subcutaneous tissue.
Histopathological picture is characterized by reticulate tunnels lined by hyperplastic epithelium. Often there are remnants of inflammation even in old scars of this type. In rolling scars, inflammation extends beyond the hair follicle, into the surrounding subcuticular area, the sweat glands and along the vascular channels, it causes wide and deep scarring, leading to rolling scars. Rolling scars are due to tethering of the epidermis and dermis to the underlying subcutaneous tissue. The surface often has a normal texture. They are wider than deeper
(Fig. 3).
Boxcar scars are round, oval or irregular depressions with sharp vertical edges.
They are wider at the
surface than ice pick scars and do not taper to a point. They appear
punched out and may be shallow or deep
(Fig. 4).
Linear scars occur when there is extensive dermal inflammation. They appear as linear atrophic, hypopigmented lines, with relatively normal skin in between. They may be narrow linear scars, where they appear as thin lines or
broad linear scars, appearing as linear dermal depressions
(Fig. 5).
Bridging scars occur when there is recurrent inflammation in a particular area, resulting in multichanneled tracts. Foul smelling sebum and epithelial debris often collects in the tracts
(Fig. 6).
Perifollicular or papular scars are hypopigmented or skin colored elevated scars that result from destruction of collagen and elastin fibers in the dermal tissues around the hair follicles. They are most common on the trunk, chin and nose
(Figs 7A and B).
Lipoatrophic scars forms when there is extensive prolonged inflammation as in cystic acne, the inflammatory mediators destroy the facial fat. The cystic lesions are also space
occupying and their eventual involution leaves an empty space that
cannot be filled by the atrophied subcutaneous tissues. Instead the
tissues are drawn in from surface layers, leading to severe depression,
and this effect is worsened by the contracture of the tissues around
these cysts
(Fig. 8).
This cystic involution and maturation followed by fibrosis probably explains the incongruous worsening of a patient’s appearance that is occasionally seen after treatment of cystic acne, especially by isotretinoin. This type of scarring becomes worse as the patient ages.3 Hypertrophic scars occur because of excess collagen deposition and decreased collagenase activity.
They appear pink or skin colored, firm and raised, commonly seen on the mandibular area, shoulders, chest and back
(Fig. 9).
There are thick hyalinized collagen bundles similar to that of other dermal scars. Keloids appear as reddish-purple papules and nodules that extend beyond the borders of the original acne lesion and may be itchy or painful. Histologically, they are characterized by thick bundles of hyalinized acellular collagen arranged in whorls.
Scarring in acne occurs due to inflammation. Controlling inflammation early and adequately is the key to preventing postacne scars.
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