ABSTRACT
Pigmentation of the hair fiber is a result of interactions between dermal papilla fibroblasts, matrix keratinocytes, and follicular melanocytes. Hair pigmentation is influenced by the ratio, number, and types of melanin granules found in the cortex of the hair fiber. Unlike ongoing pigmentation in the epidermis, active hair pigmentation is tightly coupled with the hair cycle and only occurs during the anagen, the hair growth stage. Red hair phenotypes are associated with pale skin, tendency to burn rather than tan, and increased risk for development of nonmelanoma and melanoma skin cancer. Disorders that cause hypopigmentation or depigmentation of the hair typically have diffuse effects from birth or cause poliosis circumscripta due to genetic diseases or acquired conditions. Oculocutaneous albinisim (OCA) is a group of autosomal recessive genetic diseases in which melanocytes lack the ability, to varying degrees, to produce melanin due to inborn errors in metabolism. Exact color of hair and skin is influenced both by OCA type and ethnicity.
