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[1] Melanism is the congenital excess of melanin in an organism resulting in dark pigment . Pseudomelanism, also called abundism, is another variant of pigmentation, identifiable by dark spots or enlarged stripes, which cover a large part of the body of the animal, making it appear melanistic.
Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by melanocytes at the lower layer of the epidermis . Melanin is a class of pigment responsible for producing color in the body in places such as the eyes, skin, and hair.
Hyperpigmentation results from an increase in melanin synthesis, which is mostly brought on by sun exposure, dermatological disorders, hormones, aging, genetic factors, skin injuries or inflammation, and acne. Sun exposure, which greatly increases the synthesis of melanin, is the most common cause of hyperpigmentation.
The POMC gene is located on chromosome 2p23.3. The POMC gene is expressed in both the anterior and intermediate lobes of the pituitary gland. This gene encodes a 285-amino acid polypeptide hormone precursor that undergoes extensive, tissue-specific, post-translational processing via cleavage by subtilisin-like enzymes known as prohormone convertases.
Melanocytes are melanin-producing neural crest-derived [3] cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), [4] the inner ear, [5] vaginal epithelium, [6] meninges, [7] bones, [8] and heart found in many mammals and birds. [9] Melanin is a dark pigment primarily responsible ...
Melasma (also known as chloasma faciei, [1]: 854 or the mask of pregnancy [2] when present in pregnant women) is a tan or dark skin discoloration.Melasma is thought to be caused by sun exposure, genetic predisposition, hormone changes, and skin irritation. [3]
Postinflammatory hyperpigmentation (PIH) is a skin condition characterized by the darkening of the skin (hyperpigmentation) following an inflammatory injury, such as acne, dermatitis, infectious disease, or trauma. Less frequently, it may occur as a complication of a medical procedure performed on the skin. It is a common cause of skin ...
Acanthosis nigricans is a medical sign characterised by brown-to-black, poorly defined, velvety hyperpigmentation of the skin. [1] It is usually found in body folds, [2] such as the posterior and lateral folds of the neck, the armpits, groin, navel, forehead and other areas.