Computer-assisted alignment and tracking of acne lesions indicate that most inflammatory lesions arise from comedones and de novo

Background: Inflammatory acne lesions are believed to derive from comedones; however, their evolution has not been rigorously studied. Objective: To examine the evolution of facial acne lesions using serial digital photographs and spatial alignment software. Methods: Six predefined lesion types, including inflammatory lesions, were counted and tracked from photographs taken every 2 weeks for 12 weeks from 25 individuals with untreated facial acne. Results: Closed comedones occurred most frequently (37%), followed by erythematous macules (26%), inflammatory papules (15%), open comedones (12%), pustules (2%), and nodules (1%). Inflammatory lesions were preceded by comedones (54%), normal-appearing skin (28%), erythematous macules (12%), and scars (6%). Limitations: Lesions could have appeared and resolved within the 2-week intervals and some comedones may have been too small to identify on digital photographs. Conclusion: Our results confirm the comedonal origin of the majority of inflammatory acne lesions. However, a sizeable number (28%) appear to arise from normal skin.