Pigmentation Disorders: A Short Review

Agents that give rise to skin color are skin thickness, the skin’s light refraction and absorption properties, vascular status, levels of oxidized and reduced hemoglobin, carotenoid content and, most importantly, the pigment melanin. Melanocytes, cells responsible for pigment formation, are present in the basal layer. Melanocytes are most concentrated in the central part of the face and most sparsely present in the distal part of the nail. Melanocytes have dendrites and melanin containing intracellular organelles (melanosomes). Melanin synthesis takes place inside these melanosomes through the conversion of tyrosine by the enzyme tyrosinase, first into dihydroxyphenylanine (DOPA) and then into DOPA-quinone, and subsequently into eumelanin, which bestows black-brown color, and pheomelanin, which bestows yellow-red. Pigmentation may be defined as color changes occurring in the skin, hair and eyes due to genetic heterogeneity, levels and location of melanocytes and melanin producing cells. The scope of genetic heterogeneity can range from a normal structure to pathological pigmentation phenotypes. Normal human pigmentation includes punctuate pigmentation such as ephelides and melanocytic nevi and various skin and hair colors, while the clinical appearance of abnormal human pigmentation involves hyper-, hypo or depigmentation due to increased, decreased or absence of pigment levels. Pigmentation disorders may also be classified as congenital or acquired [1].