Histochemical Study of Vitiligo in Sohag University Hospital Patients

Overview

Vitiligo is a common acquired idiopathic disorder characterized by depigmentation of the skin, hair, and mucous membranes in the form of macules and patches due to selective melanocyte destruction . Incidence of Vitiligo is about 0.5% to 2% of the world's population, and its incidence continues to increase. Vitiligo can appear at any age group especially in the second and third decades of life. About one-third of vitiligo patients are children under ten years old Vitiligo can be classified into non-segmental, segmental, mixed and unclassifiable/undetermined types. Vitiligo has a negative impact on patient's quality of life by decreasing their self-confidence and causing significant psychological distress.

The pathogenesis of vitiligo is still unclear but some theories can explain it such as oxidative stress, autoimmunity, autocytotoxicity, genetic factors, neural and melanocytorrhagy . Loss of pigment which occur in vitiligo may be due to two main causes: absence of melanocytes and/or the inability of melanocytes to produce and store melanin in melanosomes in the process of melanogenesis. High mobility group box protein B1 (HMGB1) normally presents in the nucleus to maintain genomic stabilization and regulate gene transcription. but, HMGB1 can be released outside the cell due to exposure to stressful factors such as oxidative stress and function as a damage-associated molecular pattern (DAMP) protein leading to strong proinflammatory effects. Recent data showed that HMGB1 is overexpressed in both blood and lesional specimens from vitiligo patients. Moreover, oxidative stress triggers the release of HMGB1 from keratinocytes and melanocytes, indicating that HMGB1 may participate and play a crucial role in the pathological process of vitiligo. HMGB1 Directly induces Melanocyte apoptosis through stimulation with reactive oxidative stress (ROS) or ultraviolet B (UVB) in vitro which significantly increases the release of HMGB1 from keratinocytes, which inhibits the expression of melanogenesis-related molecules such as microphthalmia- associated transcription factor (MITF), tyrosinase-related proteins and the gp100 protein in a paracrine manner and finally activate caspase-3 to trigger melanocyte apoptosis