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What is Hyperpigmentation and explain in detail?
Hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.

Causes
Hyperpigmentation can be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris.: 854  People with darker skin tones are more prone to hyperpigmentation, especially with excess sun exposure.Many forms of hyperpigmentation are caused by an excess production of melanin. 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. The process of melanin synthesis (melanogenesis) starts with the oxidation of L-tyrosine to L-DOPA by the enzyme tyrosine hydroxylase, then to L-Dopaquinone and Dopachrome, which forms melanin.As the body ages, melanocyte distribution becomes less diffuse and its regulation less controlled by the body. UV light stimulates melanocyte activity, and where concentration of the cells is greater, hyperpigmentation occurs. Another form of hyperpigmentation is post inflammatory hyperpigmentation