Vitiligo

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Vitiligo
Classification & external resources
Young woman with Vitiligo
ICD-10 L80.
ICD-9 709.01
OMIM 193200
DiseasesDB 13965
MedlinePlus 000831
eMedicine derm/453 

Vitiligo (IPA /ˌvɪtəˈlaɪgo/) or leukodermia is a chronic skin condition that causes loss of pigment, resulting in irregular pale patches of skin. The precise cause of vitiligo is complex and not fully understood. There is some evidence suggesting it is caused by a combination of auto-immune, genetic, and environmental factors. The population incidence in the United States is considered to be between 1% and 2%.

Contents

[edit] Signs

Half of people with vitiligo develop patches of de-pigmented skin appearing on extremities before their 20s. The patches may grow or remain constant in size. Patches often occur symmetrically across both sides on the body. Occasionally small areas may repigment as they are recolonised by melanocytes. The location of vitiligo affected skin changes over time, with some patches re-pigmenting and others becoming affected.

In some cases, mild trauma to an area of skin seems to cause new patches - for example around the ankles (caused by friction with shoes or sneakers). Vitiligo may also be caused by stress that affects the immune system, leading the body to react and start eliminating skin pigment.

Vitiligo on the scalp may affect the color of the hair (though not always), leaving white patches or streaks. It will similarly affect facial and body hair.

[edit] Disease mechanism

Vitiligo is associated with autoimmune and inflammatory diseases, commonly thyroid overexpression and underexpression. Jin[1][2] in the New England Journal of Medicine reported a study comparing 656 people with and without vitiligo in 114 families, which found several mutations (single-nucleotide polymorphisms) in the NALP1 gene. The NALP1 gene, which is on chromosome 17 located at 17p13, is on a cascade that regulates inflammation and cell death, including myeloid and lymphoid cells, which are white cells that are part of the immune response. NALP1 is expressed at high levels in T cells and Langerhan's cells, white cells that are involved in skin autoimmunity.

Among the inflammatory products of NALP1 are caspase 1 and caspase 5, which activate the inflammatory cytokine interleukin-1β. Interleukin-1β is expressed at high levels in patients with vitiligo. There are compounds which inhibit caspase and interleukin-1β, and so might be useful drugs for vitiligo and associated autoimmune diseases.

Of the 656 people, 219 had vitiligo only, 70 had vitiligo with autoimmune thyroid disease, and 60 had vitiligo and other autoimmune diseases.

In one of the mutations, the amino acid leucine in the NALP1 protein was replaced by histidine (Leu155->His). The original protein and sequence is highly conserved in evolution, and found in humans, chimpanzee, rhesus monkey, and bush baby, which means that it's an important protein and an alteration is likely to be harmful.

The following is the normal DNA and protein sequence in the NALP1 gene:

TCA CTC CTC TAC CAA
Ser Leu Leu Tyr Gln
S L L Y Q

In some cases of vitiligo the first leucine is altered to histidine, by a Leu155→His mutation:

TCA CAC CTC TAC CAA
Ser His Leu Tyr Gln
S H L Y Q

(Leucine is nonpolar and hydrophobic; histidine is positively charged and hydrophilic, so it is unlikely to serve the same function. [3] [4])

This page[5] contains the sequence of the DNA code for NALP1. You can search for TCACTCCTCTACCAA to find the normal sequence. In some of these vitiligo families, the sequence was TCACACCTCTACCAA.

This page[6] contains the amino acid sequence of the normal NALP1 protein (produced by that DNA sequence). You can search for SLLYQ to find the normal amino acid sequence. If this sequence came from one of the vitiligo families, its sequence would be SHLYQ.

[edit] Psychological effects

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Vitiligo can have a significant effect on the psychological well being of the patient.[7] This is especially true for darker skinned patients as the contrast between pigmented and depigmented skin can be quite drastic.

In some cultures there is a stigma attached to having vitiligo. Those affected with the condition are sometimes thought to be evil or diseased and are sometimes shunned by others in the community. People with vitiligo may feel depressed because of this stigma or because their appearance has changed dramatically.

Other people with vitiligo experience no negative psychological effects at all.

[edit] Treatment

There are a number of ways to alter the appearance of vitiligo without addressing its underlying cause. In mild cases, vitiligo patches can be hidden with makeup or other cosmetic solutions. If the affected person is pale-skinned, the patches can be made less visible by avoiding sunlight and the sun tanning of unaffected skin. However, exposure to sunlight may also cause the melanocytes to regenerate to allow the pigmentation to come back to its original color.

Phototherapy is also beneficial. Exposure to long-wave ultraviolet (UVA) light from the sun or from UVA lamps, together with Psoralen, called "PUVA", can help in many cases. Psoralen can be taken in a pill 1-2 hours before the exposure or as a Psoralen bath or soaking the area before the exposure.

Lately, PUVA has been replaced with exposure to Narrowband UVB light at a wavelength of 311-313 nanometers. This treatment does not involve Psoralen since the effect of the lamp is strong enough. The source for the UVB Narrowband UVB light can be special fluorecent lamps that treat large area in few minutes, or high power fiber-optic devices in a fraction of a second.

Scientific studies have also shown that immunomodulator creams such as Protopic and Elidel also cause repigmentation in some cases, when used with UVB Narrowband treatments [2][3].

Alternatively, some people with vitiligo opt for chemical depigmentation, which uses 20% monobenzylether of hydroquinone. This process is irreversible and generally ends up with complete or mostly complete depigmentation.

In late October of 2004, doctors successfully transplanted melanocytes to vitiligo affected areas, effectively repigmenting the region. The procedure involved taking a thin layer of pigmented skin from the patient's gluteal region. Melanocytes were then separated out and used to make a cellular suspension. The area to be treated was then ablated with a medical laser, and the melanocyte graft applied. Three weeks later, the area was exposed to UV light repeatedly for two months. Between 73 and 84 percent of patients experienced nearly complete repigmentation of their skin. The longevity of the repigmentation differed from person to person.[8]

The more traditional treatment given by most dermatologists is steroids.

[edit] Support organizations

Support groups and organizations are available to help people learn more about vitiligo, understand treatment options, and find support from other people with vitiligo.

Vitiligo Support International is the largest vitiligo organization in the world. The nonprofit organization provides free access to online message boards, chat rooms, frequently asked questions, information and articles, as well as a patient-referred doctor search. The group advocates on behalf of patients, conducts patient conferences and has local support groups.

The American Vitiligo Research Foundation Inc. (AVRF) is a non-profit, tax-exempt charity that aims to increase public awareness about vitiligo and to help those affected by vitiligo, focusing specifically on children and their families. It supports finding a cure through alternatives to animal testing.

[edit] Famous people with vitiligo

[edit] Vitiligo in domestic animals

Vitiligo is sometimes considered a cosmetic defect in the Rottweiler (this dog under anesthesia)
Vitiligo is sometimes considered a cosmetic defect in the Rottweiler (this dog under anesthesia)

Vitiligo, along with poliosis is seen as a familial trait in domestic animals. It is especially common in Arabian horses (called Arabian Pinky Syndrome) and in Rottweiler dogs.

[edit] See also

  • Alphos, the skin leprosy originally called vitiligo.
  • Albinism, a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair.

[edit] References

  1. ^ Gregersen, P.K. (March 22, 2007). "Modern genetics, ancient defenses, and potential therapies.". N Engl J Med. 356: 1263-6. Retrieved on 2007-3-25. [PMID 17377166]
  2. ^ Jin, Ying (March 22, 2007). "NALP1 in vitiligo-associated multiple autoimmune disease.". N Engl J Med. 356: 1216-25. Retrieved on 2007-3-25. [PMID 17377159]
  3. ^ List of Amino Acids and Their Abbreviations
  4. ^ The Genetic Code (DNA)
  5. ^ [1] Ensembl Transcript Report Ensembl Transcript ID: NST00000262467
  6. ^ Ensembl Protein Report Ensembl Peptide: ID ENSP00000262467
  7. ^ A. Mechri, M. Amri, A.A. Douarika, B.H. Ali Hichem, B. Zouari, J. Zili. [Psychiatric morbidity and quality of life in Vitiligo: a case controlled study]. La Tunisie médicale. 2006 Oct;84(10):632-5.
  8. ^ [PMID 15492182]
  • Grimes PE (2005). "New insights and new therapies in vitiligo". JAMA 293 (6): 730-5. PMID 15701915. 
  • Handa S, Kaur I (1999). "Vitiligo: clinical findings in 1436 patients". J Dermatol 26 (10): 653-7. PMID 10554431. 

[edit] External links

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