الفهرس 
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Abstract
Melasma is a chronic cutaneous condition characterized by irregular brown patches on sun-exposed areas of the face such as the cheeks, forehead, and upper lip and commonly occurs in women. The pathogenesis of melasma is poorly understood, but contributing factors include sun exposure, hormonal factors, genetics, pregnancy, and systemic medications (Polder and Bruce, 2012) this condition is often distressing to the patient and significantly affects quality of life measures(Pawaskar et al.,2007).
Melasma frequently affects darker Fitzpatrick skin types, which poses a challenge to treating physicians, because the armamentarium of treatment options also frequently has risks of pigmentary alteration (Graber et al., 2008). Many therapeutic modalities have been tried, with limited success, because melasma has a high tendency to recur. Treatments include the judicious use of sun protection, sun avoidance, bleaching agents, Intense pulsed light and lasers (Polder and Bruce, 2012).
The novel concept of fractional photothermolysis was introduced to the market in 2003 as an answer to the need for effective, yet low risk, resurfacing techniques. Unlike conventional lasers, fractional ablative and non-ablative photothermolysis treat only a fraction of the skin, leaving the undamaged surrounding tissue as a reservoir of viable tissue, permitting rapid epidermal repair (Bogdan-Allemann and Kaufman 2010).
The aim of our work was the study of the clinical, histopathological and immunohistochemical changes in melasma patients treated with fractional Er:YAG laser and also to compare these changes in patients treated with fractional Er:YAG laser alone or combined with topical steroid.
Fifteen Patients were treated with fractional Er:YAG 2940 nm laser while another seven patients were treated with fractional Er:YAG laser on both sides of the face and with use of topical steroid on the left side of the face to make left to right side comparison in those patients.
Our study has demonstrated that there was clinical improvement after fractional Er:YAG laser (The total of excellent, very good and good scores were73.3% of the patients). Also a 43 % decrease in MASI score after treatment when compared with that before treatment. Patients with skin type III showed statistically significant decrease of mean MASI score after treatment while patients with skin type IV showed statistically insignificant decrease in mean MASI score after treatment.
As regard histiopathological changes of fractional Er:YAG laser treated patients, H&E microscopic examination of biopsies taken from melasma showed basal hyperpigmentation in all cases which showed significant decrease after treatment. By Masson-Fontana stained sections, we have demonstrated that the MPSA/ESA percentage was significantly lower after treatment. In Masson trichrome stained sections there is reorganization of collagen bundles. Immunohistochemical staining using MART-1 antibody revealed a significant quantitative decrease in the number of melanocytes after treatment.