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

Inflammatory acne lesions are believed to derive from comedones; however, their evolution has not been rigorously studied.

To examine the evolution of facial acne lesions using serial digital photographs and spatial alignment software.

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.

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%).

Lesions could have appeared and resolved within the 2-week intervals and some comedones may have been too small to identify on digital photographs.

Our results confirm the comedonal origin of the majority of inflammatory acne lesions. However, a sizeable number (28%) appear to arise from normal skin.