Evolution and duration of nodules in severe nodular acne on the back: results from a four-week non-interventional, prospective study.

Background Severe nodular acne is characterized by inflammatory nodules and scarring. Their natural evolution and duration are insufficiently investigated. Aim To investigate the evolution and duration of untreated acne nodules. Methodology Four-week, single-centre, non-interventional, prospective study in subjects with severe nodular acne on the back. Nodule evolution and duration was assessed using standardized photographs taken twice weekly. Results Data from 23 subjects were evaluable. Mean age was 25.1 +/- 4.9 years, 87% were males, and mean acne duration was 9.7 +/- 6.7 years. At baseline, the overall total nodule count was 132 (mean number: 5.7 +/- 3.0 nodules/subject). Among others, the following two main pathways were observed: nodules evolving directly into atrophic scars (31.8%) and nodules evolving towards papules into atrophic scars (37.9%). After 4 weeks, 77.3% of baseline nodules had evolved into atrophic scars. After baseline visit, a total of 247 new nodules (3.1 +/- 2.2 nodules/week/subject) with a mean duration of 4.9 +/- 2.6 days were observed. The mean duration of new nodules was significantly longer in subjects (n = 16) with >= 6 new nodules compared to subjects (n = 7) with <6 new nodules (5.2 +/- 1.4 vs. 3.6 +/- 0.8 days; P = 0.008)). There was no correlation between the number of new nodules and acne duration or with the number of baseline nodules. Conclusion This study documents the natural nodule evolution and duration over 4 weeks and showed in 23 patients the scarring potential of untreated severe nodular acne of the back.