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White or pale discoloration on skin occurs due to hypopigmentation (diminished pigmentation). The epidermis layer of skin has melanin pigment which gives different hues ranging right from white to dark black.
There are also conditions wherein white hypopigmentation occurs due to some other factors like lack of vitamins, congenital conditions, autoimmune diseases, injuries, infections etc.
White discoloration on skin due to albinism
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Albinism (achromia) is a hypopigmentary disorder which is congenital.
Albinism results from defect in production of melanin pigment due to dysfunction of melanocytes (melanin producing cells) in the skin, hair and eyes.
Albinism can be complete or partial leading to degrees of absence of melanin pigment in the hair, epidermis and eyes.
Two main clinical phenotype categories of albinism are ocular albinism and oculocutaneous albinism which are further categorized into subtypes based on specific genetic mutations. This genetic white color occurs due to mutations to the tyrosinase gene and several different types of mutations can occur. Certain mutations can lead to completely inactive tyrosine enzyme production resulting in total albinism.
In some mutations tyrosine enzyme may have reduced activity (leaky mutations) and partial albinism may result. Mutations to P protein gene and human gene coding for TRP-1 also produce varying degrees of albinism.
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Leucism
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This type of white discoloration on the skin is a result of defects in neural crest pigment cell differentiation. Unlike albinism wherein the melanocytes are very much present but they fail to produce melanin pigment only, here the discoloration is caused due to defect in the embryonic development. There is partial or complete absence of pigment cells.
In partial absence of skin pigment cells 'piebald' effect is seen with varying degree of pigment absence leading to spotted pigmentation. Another difference between albinism and leucism is that albinos lack skin pigment in both iris and the retinal pigmented epithelium (RPE) leading to red color of the internal blood vessels showing up as red eyes.
However the formation of iris and the retinal pigmented epithelium is by the outpouching of the neural tube during development and is not affected by the neural crest aberration. Hence the eye color is not affected and has normal pigmentation in leucism.
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White discoloration on skin due to vitiligo
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In this chronic disorder loss of pigment (depigmentation) occurs in patches leading aesthetic disfigurement of the affected individual.
Though the very exact cause of this white hypopigmentation - hypomelanosis is not known, most of the researchers agree that autoimmunity, neural, oxidative stress, genetic or viral causes precipitate the death and destruction of melanocytes.
These depigmentation patches affecting the normal human skin color, occur usually on the extremities and around body orifices like umbilicus, mouth, genitalia, nostrils and eyes.There are different types of vitiligo and now various treatments are available for eradication or camouflage of the white patches.
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Leprosy and white discoloration on skin
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Leprosy or Hansen's disease (HD), which is now on the verge of eradication from the world population, is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Dermal lesions are the initial external signs, characterized by one or more hypopigmented macules or patches.
These white patches are anaesthetic in nature where sensations are lost. This is due to damage caused by human immune cells on the peripheral nerves. Leprosy can be cured completely and if detected early damages to nerves, dermis, eyes and limbs can be prevented.
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White discoloration on skin due to tinea versicolor
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Tinea versicolor is caused by yeasts (fungi) Malassezia globosa and Malassezia furfur.
Tinea versicolor, though a common microbe living on the skin, sometimes over grows in some people and the exact reason is not clear. However, tinea versicolor is found to affect people with oily epidermis and in tropical and humid climates.
The first signs of tinea versicolor infection are small hypopigmented spots, usually lighter than the surrounding area, developing on the oily areas of the body, such as back, upper arms and shoulder giving rise to itching. The white coloration caused by tinea versicolor can be effectively treated and cured with anti-fungal lotions.
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Idiopathic guttate hypomelanosis
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Idiopathic guttate hypomelanosis is a non-infectious common benign acquired disorder of the skin affecting women more frequently than men.
Idiopathic guttate hypomelanosis white discoloration appears to affect the exposed areas of the body, more particularly forearms and legs, in late twenties.
Idiopathic guttate hypomelanosis appears as small drops-like spots of white discoloration, the exact cause of which is not clear. However, as they appear on the exposed parts of the body, exposure to sun may have some role on the melanocytes making them effete.
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Nevus depigmentosus
- Nevus depigmentosus are harmless non-progressive hypopigmented stable localized skin patches. Nevus depigmentosus patches result from localized abnormalities in the function of melanocytes which fail to produce pigments. Most of the nevus depigmentosus patches are usually present right from birth.
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Pityriasis alba
- Pityriasis alba is a common and highly prevalent facial condition occurring in children. Pityriasis alba appears as dry, fine-scaled, white patches especially on the face. Pityriasis alba is a non-contagious condition and resolves by itself after sometime. Use of moisturizers improves the scaly condition especially in winter.
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Avitaminosis and white skin discoloration
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The chronic lack of certain vitamins, especially vitamins of the B complex group in the diet can cause hypopigmentation.
This white skin hypopigmentation can be corrected by improving the quality of diet and taking vitamin supplements.
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