Coordinates | 28°36′50″N77°12′32″N |
---|---|
Name | Vitiligo |
Diseasesdb | 13965 |
Icd10 | |
Icd9 | |
Omim | 193200 |
Medlineplus | 000831 |
Emedicinesubj | derm |
Emedicinetopic | 453 |
Meshid | D014820 }} |
Classes of non-segmental Vitiligo include: Generalized Vitiligo: the most common pattern, wide and randomly distributed areas of depigmentation Universal Vitiligo: depigmentation encompasses most of the body Focal Vitiligo: one or a few scattered macules in one area, most common in children Acrofacial Vitiligo: fingers and periorificial areas Mucosal Vitiligo: depigmentation of only the mucous membranes
In one case, the gene TYR, which makes the melanocyte more susceptible to the immune system in vitiligo, also makes the melanocyte more susceptible to the immune system in the skin cancer malignant melanoma. So people with vitiligo caused by the TYR gene are less likely to have malignant melanoma.
A genomewide association study found 10 independent susceptibility loci for generalized vitiligo, responsible for 7.4% of the genetic risk. Some patients had vitiligo alone; others had generalized vitiligo with other autoimmune diseases. Most loci were associated with both forms. (The exception was PTPN22, which was only associated with generalized vitiligo.) In the MHC region, which controls the immune system, major association signals were identified in the class I gene region (between HLA-A and HLA-HGC9) and class II gene region (between HLA-DRB1 and HLA-DQA1). Outside the MHC region, association signals were identified near RERE, PTPN22, LPP, IL2RA, GZMB, UBASH3A and C1QTNF6 genes, which are associated with other autoimmune diseases. TYR encodes tyrosinase, which is not a component of the immune system, but is an enzyme of the melanocyte that catalyzes melanin biosynthesis, and a major autoantigen in generalized vitiligo. The major alleles of TYR are associated with vitiligo, and the minor alleles are associated with malignant melanoma. Vitiligo-associated 402R tyrosinase may be more efficiently presented to the immune system. Melanoma-associated 402Q may fail to be identified by the immune system.
The transcriptional profile of melanocytes from vitiligo patients have been studied. Oligonucleotide microarrays containing approximately 16,000 unique genes were used to analyse mRNA expression in melanocytes from vitiligo patients and age-matched healthy controls. In total, 859 genes were identified as differentially expressed.
Vitiligo is sometimes associated with autoimmune and inflammatory diseases, commonly thyroid overexpression and underexpression. A study comparing 656 people with and without vitiligo in 114 families 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 cells, white blood cells that are involved in skin autoimmunity. Polymorphisms of CD4 were shown to be associated with the vitiligo and other autoimmune diseases like type I Diabetes Mellitus.
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. 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 is an important protein and an alteration is likely to be harmful. Addison's disease (typically an autoimmune destruction of the adrenal glands) may cause vitiligo.
Studies have shown that immunomodulator creams such as Protopic and Elidel also cause repigmentation in some cases, when used with UVB narrowband treatments.
A 1997 report suggests that combining Vitamin B12 and folic acid supplements with sun exposure caused repigmentation in 52% of cases.
In October 1993, a scientific report was published of successfully transplanting 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 to a cellular suspension that was expanded in culture. The area to be treated was then denuded with a dermabrader and the melanocytes graft applied. Between 70 and 85 percent of patients experienced nearly complete repigmentation of their skin. The longevity of the repigmentation differed from person to person.
Ultraviolet light (UVA) treatments are normally carried out in a hospital clinic. Psoralen and Ultraviolet A light (PUVA) treatment involves taking a drug which makes the skin very sensitive to light. The skin is then exposed to ultraviolet A light (UVA). Treatment is required twice a week for 6–12 months or longer. PUVA may cause side effects such as 'sunburn' type reactions or skin freckling. Narrowband ultraviolet B (UVB) phototherapy is now used more commonly than PUVA as it is less damaging to the skin. As with PUVA, treatment is carried out twice weekly but there is no requirement to pre-sensitise the skin and the treatment sessions are much shorter.
A few preliminary trials have been carried out using the herb ginkgo biloba. A small scale open label pilot clinical trial found the progression of vitiligo stopped in all participants; the total VASI (Vitiligo Area Scoring Index) indicated an average repigmentation of vitiligo lesions of 15%. The authors conclude "Larger, randomized double-blind clinical studies are warranted and appear feasible."
A direct correlation of Vitiligo was found with another auto immune disease, Celiac Disease. When one patient's Celiac Disease was treated with a Gluten free diet, Vitiligo lesions of 20 years repigmented 50% over a 5 year period.
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