Pigmentary

Pigmentary is an adjective relating to pigment or pigmentation, the coloring matter produced by, or found within, living tissues. In biology, pigmentary systems include pigments such as melanin, carotenoids, and hemoproteins that give color to skin, hair, eyes, feathers, plants, and other tissues. The study of pigmentary processes covers the production, distribution, and preservation of pigments as well as how they influence visual appearance and protective functions.

In humans, melanin is the dominant pigment in the skin. It is synthesized in specialized cells called melanocytes, within membrane-bound melanosomes, through a biochemical pathway called melanogenesis that depends on the enzyme tyrosinase and related enzymes. Melanin production is influenced by genetics, notably variants in pigmentation genes such as MC1R, OCA2, TYR, and SLC45A2, and by ultraviolet radiation, which can stimulate increased melanin synthesis as a protective response.

Pigmentary disorders refer to abnormal pigmentation. Hypopigmentation, including albinism and vitiligo, involves reduced or absent pigment. Hyperpigmentation, including melasma, post-inflammatory hyperpigmentation, and lentigines, results from excess pigment production or deposition. Pigmentary changes can accompany inflammatory, infectious, or metabolic conditions and may vary by age, ethnicity, and hormonal status.

Beyond skin, pigmentary processes are important in other tissues. The retinal pigment epithelium contains pigment that supports vision and can undergo pigmentary changes in diseases such as retinitis pigmentosa or age-related macular degeneration. In animals and plants, pigmentary systems contribute to camouflage, mating signaling, photosynthesis, and UV protection.