[Long-term effect of botulinum toxin type A injection on hypertrophic acne scar].

Objective: To investigate both the short-and long-term effect of botulinum toxin type A (BTXA) injection on hypertrophic ache scar.

Methods: A total of 26 patients with acne scar received BTXA injection of within 100 units. The effect was evaluated using the ECCA grading scale before treatment and during clinic re-visit, which based on history of acne scar and number of scar area.The short-and long-term effect was recorded. The average follow-up period was 39.23 months. All results were evaluated by SPSS 21.0.ANOVA was used to evaluate average value and standard deviation of ECCA grading scale. Kaplan-Meier survival curve was used to evaluate relapse-free period, and Pearson test was used to detect relevant factors of relapse-free period.

Results The BTXA injection showed significant positive long-term effect on inflammatory or hypertrophic acne scar. The average ECCA grading scale was 103.460 ±36.872 before treatment,79.620 ±37.146 at 6 months after treatment,63.160 ±24.049 at 12 months after treatment,47.500 ±4.629 at 18 months after treatment, and 50.000 ± 0.000 at 24 months after treatment,showing significant differences between any of two groups (P ＜ 0.01).Average relapse free period was 28.354 ± 1.775 months. Relapse-free period was related to ECCA grading scale pre treatment and injection times (P ＜ 0.01); meanwhile, dose of BTXA and length of disease all had statistical significance (P ＜ 0.05); however, age and gender had no statistical significance (P ＞ 0.05).

Conclusions: The BTXA injection can relieve inflammation and improve scar texture in patients with hypertrophic acne scar in both the short-and long-term follow-up.