Color in the human skin is because of various pigments and the blood circulating through the skin. Off all the pigments melanin is the most important which can vary from race to race and between different individuals of the same race. The amount of melanin present in the skin of and individual primarily determines the skin color of that individual. A few other pigments may sometime accumulate in the skin, like hemosiderin and additional ting of other colors in certain abnormal conditions.

Some diseases may also affect the pigmentation of human skin and generally are a source of big concern for the affected person due to cosmetic considerations and the associated psychological impact.

Pigmentray disorders can be considered in various groups, for example they can be generalized or localized. And they may also be considered as hyper-pigmentary disorders. The localized disorders are generally more concerning because they are cosmetically noticeable at a very early stage.

The number of these disorders can run very high but we shall consider here only the common ones.

Generalized Hyper pigmentation

Generalized hyper-pigmentation may result from as simple causes as tanning due to excessive sun exposure or may be due to a serious underline condition. The most important in this regard is the nelson syndrome associated with Addison’s diseases.

This is a condition in which the adrenal glands fail and production of endogenous steroids falls very low. The pituitary tries to compensate for the deficiency by producing excessive corticotrophin (ACTH) which stimulates melanin pigmentation.

Generalized black pigmentation may also be same in some people with chronic renal failure and chronic hepatic failure. The diagnosis of these conditions depend basically on symptoms signs and test reports related to the name disease in which pigmentary disorder is the least important issue.

Acanthrosis Nigricans is a fairly common condition associated with patches of black pigmentation especially at the nap of neck but other areas are not immune. It is associated with insulin resistance and can be seen in most people with metabolic syndrome and type-2 diabetes.

Generalized Hypo pigmentation

Is most commonly seen in albinism but poor sun exposure can diminish the skin color very significantly especially in areas where sunshine is rare.

Pituitary disorders like hypo-pitutrisim (Sheehan’s syndrome) can be associated with pigmentary lose and a peculiar skin complexion. Fortunately this disease is not very common.

Localized hyper pigmentation

Melanin hyper pigmentation is commonly seen in the form of post inflammatory pigmentation and melasma. The less common conditions are poikiloderma of civatte, urticaria pigmtosa (mastocysis).

Some disorders of the keratin may also lead to hyper pigmentation of a different character like arithrasma, a Acanthrosis nigricans, icthyosis and xerosis. Hemosidrin is a chemical by product of hemoglobin disintegration in the body which can accumulate in disorders of the blood causing excessive destruction of red blood cell. The patient may develop a typical bronze color and if the pigment damages liver and pancreas it can result in a rare verity of diabetes called bronzed diabetes.

Localized hypo pigmentation

This topic has been discussed at length in another chapter, localized hypo pigmentation