Acne lesion count (ALC)

Acne lesion counts are a standard clinical metric used to quantify the severity of acne vulgaris and assess the efficacy of therapeutic interventions in dermatological research. This measurement involves the physical enumeration of specific skin lesions, which are subdivided into non-inflammatory lesions (open and closed comedones) and inflammatory lesions (papules, pustules, and nodules) [StatPearls: Acne Vulgaris, 2023]. In drug development, the absolute and percentage reduction in lesion counts from baseline serves as a primary efficacy endpoint required by regulatory agencies like the FDA for the approval of new acne treatments [FDA, 2005]. While the count itself is a phenotypic observation rather than a molecular target, it reflects the underlying pathological processes of the pilosebaceous unit, including hyperkeratinization, androgen-mediated sebum production, and immune responses to Cutibacterium acnes. Clinical trials typically pair lesion counts with a validated global assessment scale to provide a comprehensive view of treatment success and patient improvement.

Other names

Total lesion countInflammatory lesion countNon-inflammatory lesion countAcne lesion tallyComedone count

Acne lesion counts are clinical endpoints and do not possess a mechanism of action. However, the drugs monitored using this metric reduce counts by targeting follicular hyperkeratinization, sebum production, Propionibacterium acnes (C. acnes) proliferation, and inflammation [FDA Guidance for Industry: Acne Vulgaris, 2005].