Histologic and ultrastructural analysis of melasma after fractional resurfacing

Fractional photothermolysis is a popular treatment option for photodamaged skin and other cutaneous conditions. Recently, successful improvement in melasma has been achieved with this laser system. We undertook this study to evaluate the ultrastructural changes associated with fractional laser treatment of melasma.

Ten subjects with skin types III and IV and a clinical diagnosis of epidermal melasma were treated with a 1,550-nm erbium:glass laser delivering light in a fractional manner (Fraxel SR 750, Reliant Technologies, Inc., Mountain View, CA) every 2 weeks for a total of four sessions. Biopsies were obtained from all subjects both before treatment and at 3 months following the final treatment. All biopsies were analyzed by light and electron microscopy for treatment-induced changes. In addition, a secondary endpoint of the study was to assess for clinical improvement in melasma following fractional resurfacing. This assessment was performed by the investigator using pre- and post-treatment photographs.

Light microscopy on post-treatment specimens showed a relative decrease in melanocytes compared to the pre-treatment ones. Post-treatment electron microscopy revealed fewer melanocytes and a relative absence of melanin in the surrounding keratinocytes compared to pre-treatment specimens. In addition, six subjects with skin type III were determined to have good improvement, whereas four subjects with skin type IV had fair improvement, as assessed by the investigator.

Post-treatment ultrastructural changes are consistent with an elimination process and may help to explain clinical improvement following laser treatment.