Histologic and ultrastructural analysis of ultraviolet B laser and light source treatment of leukoderma in striae distensae.

BACKGROUND Lasers and light sources emitting ultraviolet B (UVB) irradiation have been shown to repigment striae distensae. OBJECTIVE The purpose of this study was to analyze the histologic and ultrastuctural changes seen after UVB laser- or light source-induced repigmentation of striae distensae. METHODS Ten subjects with hypopigmented striae were selected. Five subjects were treated with an XeCl excimer UVB laser, and five subjects were treated with a UVB light device. Six months after the final treatment, the biopsies were evaluated for both standard and electron microscopic changes in melanocytes. RESULTS Analyses of biopsied skin after treatment with both the UVB laser and light source showed increased melanin content, hypertrophy of melanocytes, and an increase in the number of melanocytes in all patients. CONCLUSIONS Repigmentation of striae distensae with either a UVB laser or light source is due to an increase in melanin pigment, hypertrophy of melanocytes, and an increase in melanocytes.