Vitiligo is an acquired depigmenting disorder of the skin, in which pigment cells (melanocytes) are lost. It presents with well-defined milky-white patches of skin (leukoderma). Vitiligo can be cosmetically very disabling, particularly in people with dark skin.
Vitiligo affects 0.5–1% of the population, and occurs in all races. It may be more common in India than elsewhere, with reports of up to 8.8% of the population affected. In 50% of sufferers, pigment loss begins before the age of 20, and in about 80% it begins before the age of 30 years. In 20%, other family members also have vitiligo. Males and females are equally affected.
Even though most people with vitiligo are in good general health, they face a greater risk of having autoimmune diseases such as diabetes, thyroid disease (in 20% of patients over 20 years with vitiligo), pernicious anaemia (B12 deficiency), Addison disease (adrenal gland disease), systemic lupus erythematosus, rheumatoid arthritis, psoriasis, and alopecia areata (round patches of hair loss).
what causes vitiligo?
Vitiligo is due to loss or destruction of melanocytes, which are the cells that produce melanin. Melanin determines the colour of skin, hair, and eyes. If melanocytes cannot form melanin or if their number decreases, skin colour becomes progressively lighter.
The exact cause of vitiligo is unknown. It is thought to be a systemic autoimmune disorder, associated with deregulated innate immune response, although this has been disputed for segmental vitiligo. There is a genetic susceptibility and vitiligo is a component of some rare syndromes. The gene encoding the melanocyte enzyme tyrosinase, TYR, is likely involved.
There are three theories on the cause of vitiligo:
The pigment cells are injured by abnormally functioning nerve cells
There may be an autoimmune reaction against the pigment cells
Autotoxic theory – the pigment cells self-destruct
what are the clinical features of vitiligo?
Vitiligo can affect any part of the body. Complete loss of pigment can affect a single patch of skin or it may affect multiple patches. Small patches or macules are sometimes described as confetti-like.
Common sites are exposed areas (face, neck, eyelids, nostrils, finger tips and toes), body folds (armpits, groin), nipples, navel, lips and genitalia.
Vitiligo also favours sites of injury (cuts, scrapes, thermal burns and sunburn). This is called the Koebner phenomenon.
New-onset vitiligo also sometimes follows emotional stress.
Vitiligo may occasionally start as multiple halo naevi.
Loss of colour may also affect the hair on the scalp, eyebrows, eyelashes and body. White hair is called ‘leukotrichia’ or ‘poliosis’.
The retina at the back of the eye may also be affected. However, the colour of the iris does not change.
The colour of the edge of the white patch can vary.
It is usually the colour of unaffected skin, but sometimes it is hyperpigmented or hypopigmented.
The term trichrome vitiligo is used to describe 3 shades of skin colour. Very rarely, there are 4 shades of pigment (white, pale brown, dark brown and normal skin).
Occasionally, each patch of vitiligo has an inflamed red border.
The severity of vitiligo differs with each individual. There is no way to predict how much pigment an individual will lose or how fast it will be lost.
Vitiligo appears more obvious in patients with naturally dark skin.
Extension of vitiligo can occur over a few months, then it stabilises.
Some spontaneous repigmentation may occur. Brown spots arise from the hair follicles and the overall size of white patch may reduce.
At some time in the future, the vitiligo begins to extend again.
Cycles of pigment loss followed by periods of stability may continue indefinitely.
Light skinned people usually notice the pigment loss during the summer as the contrast between the affected skin and suntanned skin becomes more distinct.
Pigment has occasionally been reported to be lost from the entire skin surface.
how is vitiligo diagnosed?
Vitiligo is normally a clinical diagnosis, and no tests are necessary to make the diagnosis.
Occasionally skin biopsy may be recommended, particularly in early or inflammatory vitiligo, when a lymphocytic infiltration may be observed.