INTRODUCTION
Acne vulgaris is a chronic inflammatory skin disease of the pilosebaceous unit, affecting approximately 80% of young adults and adolescents.1-3 It is a polymorphic disease in which several types of lesions are usually present concurrently: primary lesions reflecting active acne (including comedones and inflammatory types) and secondary lesions which originate from active acne lesions (including scars, macular erythema, and post-inflammatory hyperpigmentation [PIH]). In addition to the diverse presentation of active acne lesions, acne scars are also highly variable, and sometimes do not correlate with acne severity (eg, scarring can occur even with mild acne). The most frequently occurring scars involve loss of tissue (atrophic scars) in diverse shapes, sizes, and degrees. Excess tissue can also occur as an acne scar, and can be categorized as hypertrophic scars and keloids (often determined by location and racial factors).4 Atrophic acne scarring is very common, with reports indicating some degree of scarring in up to >87% of patients with mild to moderate acne.5, 6 Clinically relevant atrophic scarring (mild or greater) is most frequent on the face (55% of subjects), followed by the back (24%) and chest (14%).6 Nevertheless, relatively little is known about acne scar pathophysiology, epidemiology, and natural history. A recent study of prevalence and risk factors of acne scarring found that acne severity, time between acne onset and effective treatment, and acne relapse were the most significant risk factors associated with scarring.7 In addition, patients suffering from severe inflammatory acne were 3.4 to 6.8 times more likely to develop scars compared to those with less severe acne.7 Finally, acne scars can have an important psychological impact on sufferers, contributing to self-consciousness, anxiety, depression, and in severe cases suicide.8,9 Given the paucity of literature on the evolution of acne lesions, the objective of this study was to evaluate the relationship between primary and secondary acne lesions, with a focus on the genesis of atrophic acne scars.
METHODS
Participants
Subjects were male and female aged 18 to 35 years with moderate facial acne vulgaris, defined as 20 to 40 inflammatory lesions (papules and pustules, excluding the nose), no more than 1 acne nodule, and a minimum of 10 atrophic acne scars (>1.5 mm in diameter) on each side of the face, with a relatively equivalent distribution on each side. The study was performed in accordance with Good Clinical Practice and was approved
