ABSTRACT
INTRODUCTION Mammalian skin is a dynamic organ that utilizes both passive and active protection mechanisms designed to maintain integrity and homeostasis of organism under a variety of circumstances throughout growth, from an aquatic in utero development to the challenges of a terrestrial environment (1). Responses to climate, disease, toxins, and ultraviolet light are all determined by the fitness of the skin, particularly its barrier function (2). Gaps or deficiencies in barrier function can lead to a variety of diseases with cutaneous and systemic manifestations. This chapter briefly introduces the nature of the skin’s barrier and the challenges it must address. The subsequent sections focus primarily on skin diseases associated with barrier impairment. A comprehensive discussion of all disorders associated with barrier dysfunction is not feasible, and, therefore, this chapter and the references therein will cover the most common syndromes associated with skin barrier deficiency from a clinical perspective with any appropriate background findings from appropriate in vitro and in vivo research models. A more detailed understanding of these diseases might allow for a better delineation of normal barrier physiology, for insights into further research on the complex regulatory pathways that intersect to regulate barrier function, and may open up promising avenues for therapeutic investigation. The skin can function as an endocrine organ as well, responsible for the ultraviolet light mediated conversion of dehydrocholesterol into cholecalciferol, vitamin D3 (3,4).
