Vitiligo: The comprehensive overview of epidemiology, treatment, for segmental vitiligo


Vitiligo: A comprehensive overview



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Vitiligo: A comprehensive overview : Part

II: Treatment options and approach to treatment

With the appropriate management, many patients can minimize disease progression, attain repigmentation, and achieve cosmetically pleasing results. There are numerous medical and surgical treatments aimed at repigmentation; therapies for depigmentation are available for patients with recalcitrant or advanced disease (2). Nonsurgical treatments include topical, systemic, phototherapy, photochemotherapy, BIOSKIN,and laser therapy[1,2,4,5,6]. Surgical options include skin grafting and melanocyte suspension transplantation. Alternative therapies, camouflage, psychotherapy, and depigmentation can be beneficial to patients with vitiligo[1,2] (2). Treatment efficacy varies with duration and distribution of disease, type of vitiligo, and use in combination with other modalities.

Despite treatment, many patients will continue to suffer with vitiligo throughout their entire lives. Corticosteroids (CSs) are commonly used as a first-line and adjunctive therapy for the treatment of vitiligo. Their efficacy is attributed to modulation of the immune response (2). Studies have shown an abundance of inflammatory cells in vitiligo, with a predominance of macrophages and T cells (2). Placebo studies have supported the efficacy of CS monotherapy (2).Higher response rates are seen in children compared to adults; head and neck lesions tend to have the greatest response to treatment[1,2] (2). Based on comparative studies, topical CSs are the most clinically effective choice for topical therapy. Compared with topical calcineurin inhibitors, patients treated with topical CSs had equivocal to slightly higher rates of repigmentation (2). Side effects of topical therapy include epidermal atrophy, telengectasia, striae distensae, steroid folliculitis, and side effects associated with systemic absorption. In children treated with medium to high potency topical CSs, 26% developed local side effects, and 29% had abnormal cortisol levels at follow-up (2). Cortisol levels were more affected when treating lesions on the head and neck, and, interestingly, did not correlate with steroid potency. Systemic CSs may induce insomnia, acne, agitation, menstrual disturbances, weight gain, hypertrichosis, and adrenal insufficiency (2). In one study of vitiligo patients treated with intravenous steroids, 69% reported systemic side effects (2). While systemic CSs have potential in treating patients with vitiligo, the lack of data on efficacy and optimal dosing parameters warrant further research (2).

Topical CSs are generally considered a safe first-line therapy. Head and neck lesions have the best response rates, but there is concern for systemic absorption. Local side effects may prohibit long-term use (2).

Calcineurin inhibitors (CIs) are advantageous in treating vitiligo because they have immunomodulatory effects without the side effect profile of CSs. Calcineurin is an intracellular protein in lymphocytes and dendritic cells. When activated, it acts as a transcription factor for cytokines, such as interleukin-2 (IL-2) and tumor necrosis factor–alfa (TNFα) (2). Many small clinical studies support the efficacy of topical tacrolimus and pimecrolimus when assessed after 3 and 6 months of therapy. Response rates range from 63% to 89%, with the best results seen on the head and neck (2).

UVA phototherapy is almost always given in conjunction with the photosensitizer psoralen. PUVA phototherapy induces hypertrophy of melanocytes and hyperactive melanosomes (2). It also stimulates melanocytes in hair follicles, induces keratinocyte release of factors that simulate melanocyte growth, and may reduce the presence of vitiligo-associated melanocyte antigens on melanocyte membranes[2,6] (2). Clinically, this results in perifollicular repigmentation. high doses of UVA alone (15 J/cm2) induce repigmentation of more than 60% in half of subjects (2). Enhanced with psoralen, response rates are as high as 78% and up to 100% for head and neck lesions in more than half of subjects (2). Lesions on the extremities are less responsive. NBUVB induces tyrosinase, an enzyme crucial to melanin production, and increases the presentation of HMB45 on the surface of melanosomes (2). When used alone, NBUVB phototherapy results in repigmentation rates of 41.6% to 100%. Patients are typically irradiated two to three times a week, with average treatments lasting between 10 weeks and 2 years. In children, an average of 34 treatments was required to achieve 50% repigmentation (2).

When laser is used as monotherapy, repigmentation rates of more than 75% are seen in 16.6% to 52.8% of patients; response rates are as high as 95% (2). On average, it takes 11 to 22 sessions to see repigmentation, more in poorly responsive acral areas (2). The onset of repigmentation negatively correlates with the total number of treatments. MEL results improve when used with other modalities. With topical hydrocortisone, 42.8% of patients achieved more than 75% repigmentation compared to only 16.6% using 308-nm MEL alone (2).Topical tacrolimus has similar additive effects.

Another treatment option is BIOSKIN, a new device out of Italy, Bioskin, transmits focused 311-nm UVB phototherapy (microphototherapy) [2,3,6]. The goal is to improve cosmesis, reduce adverse effects, and decrease the premature aging and risk of skin cancer associated with total body irradiation [2,3,6]. A large study of 458 subjects compared Bioskin to several other conventional topical therapies (2). Alone, Bioskin had repigmentation rates of more than 75% in 72% of patients. In combination, the best results were seen with betamethasone dipropionate (>75% repigmentation in 90.2% of subjects) (2).

In a clinical study of patients with severe vitiligo, monobenzone 20% produced depigmentation in 84% of patients, with complete depigmentation in 44% (2). In a study with hydroquinone, 69% achieved total depigmentation; however, 36% of those had some repigmentation at 2 months to 3 years of follow-up (2). The Q-switched ruby laser has been extensively used for depigmentation in vitiligo universalis, although the Q-switched alexandrite laser is also effective (2).

Although patients with SV have been studied alongside those with NSV, it is unclear how applicable study results are to this population. SV tends to be more stable and recalcitrant to treatment. The He-Ne laser works via different mechanisms more targeted to the disease process of SV, and is more effective in this population (2). Generalized/universal vitiligo may also require tailored treatment. The extent of disease can be so great that it may be nearly impossible to provide cosmetically pleasing repigmentation[1,2] (2). For these patients, depigmenting agents should be offered.


Gene expression analysis of melanocortin

system in vitiligo.

Kingo et al. aimed to analyze changes in expression of genes involved in skin pigmentation (melanocortin system and enzymes involved in melanin synthesis). With quantitative RT-PCR they measured the mRNA expression levels of eight genes from the melanocortin system and two enzymes involved in melanogenesis (3). RNA was extracted from both lesional and non-lesional skin of vitiligo patients and in non-sun-exposed skin of healthy subjects (3). POMC (proopiomelanocortin) expression was lower in lesional skin compared to non-lesional skin. Expression of melanocortin receptors was increased in unaffected skin of vitiligo patients compared to healthy subjects and decreased in lesional skin compared to uninvolved skin of vitiligo patients, the differences were statistically significant in the cases of MC1R (melanocortin receptor 1) and MC4R (melanocortin receptor 4) (3). TRP1 and DCT genes were down-regulated in lesional skin compared to non-lesional vitiligo skin or skin of healthy controls and up-regulated (3).

Several hypotheses have proposed to explain the dysfunction and/or loss of melanocytes in epidermis of vitiligo patients. These include an autoimmune mechanism, an auto-cytotoxic mechanism and an abnormality in melanocytes or in surrounding keratinocytes-producing factors necessary for the survival and function of melanocytes in uninvolved vitiligo skin compared to healthy control samples (3). The purpose of present study was to examine the expression variations of genes encoding mediators of the melanocortin system in non-lesional and lesional skin of vitiligo patients and in skin of healthy controls with the aim to explore the regulation of the cutaneous stress response system in vitiligo (3). In previous studies, a reduction in the level of the POMC peptide α-MSH has been demonstrated both in lesional skin and serum of vitiligo patients[3,5] (3).

Two skin biopsies (4 mm) were obtained from each patient with vitiligo: one from the central part of involved skin and another from non-sun-exposed uninvolved skin (3). One skin biopsy (4 mm) from non-sun-exposed skin was taken from healthy control subjects (3). The non-sun-exposed skin was defined as the skin never exposed to UVR previously and definitely not exposed to natural UVR in the last 12 months (3).

Gene expression levels of POMC, the five melanocortin receptors (MC1R–MC5R) and endogenous melanocortin receptor antagonists (ASIP and AGRP) were measured by quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) in punch biopsies from lesional and non-lesional skin of vitiligo patients (n = 31) and from non-sun-exposed skin of healthy subjects (n = 24) (3). In addition, levels of two genes encoding enzymes concerned with melanogenesis – tyrosinase-related protein-1 (TRP1) and dopachrome tautomerase (DCT) – were measured (3). The presence of mRNA expression of examined genes in skin of healthy controls and vitiligo patients became evident in QRT-PCR with a relatively large number (3) of amplification cycles (3). In the samples, MC1R demonstrated the highest expression (amplification after 27 cycles), whereas the levels of MC2R, MC3R, MC4R and MC5R mRNAs were low (amplification after 32–36 cycles). remains unclear. In the present study, POMC mRNA expression was found to be lower in lesional skin compared with non-lesional skin in the vitiligo group (p < 0.05) (3). In conclusion, the expression of genes of the melanocortin system is altered in vitiligo. Decreased expression of the genes of the melanocortin system and enzymes of melanogenesis in the lesional skin demonstrated in the present study is not surprising and fits with existing data (3).




UV-B radiation microphototherapy . An elective treatment for segmental vitiligo.


The purpose of this study was to use UV-B radiation exclusively on vitiligo patches of individuals affected by SV to evaluate the effectiveness of this therapy. Eight individuals with SV were treated for 6 months with a new device called BIOSKIN that can produce a focused beam of UV-B (microphoto-therapy) on vitiligo patches only [2,4,6] (4). After 6 months of microphototherapy five subjects of the eight studied achieved normal pigmentation on more than 75% of the treated areas (4). In particular, three of these were totally repigmented. Two individuals achieved 50-75% pigmentation of the treated areas, and only one showed less than 50% repigmentation (4). The use of ultraviolet-B (UV-B) radiation invitiligo therapy is relatively recent, it is considered presently the most effective treatment for generalized vitiligo. The successful use of UV-B rays is probably due to several direct and mediated interactions of UV-B with melanocytes, keratinocytes and skin immune system [2,4] (4).

The individuals were four men and four women with a mean age of 17.9 years and skin type I11 for six persons and I1 for the other two (4). The control group was composed of eight individuals, five men and three women, affected by SV with a mean age of 22.9 years; skin type was I11 for five persons and I1 for the other three (4). Complete treatment of a 10 cm2 diameter vitiligous area with 100 mJ requires repeating a 2-s 1 cm2 diameter spot six times with 100 mJ/ cm2 intensity (4). Each treatment session consists of irradiation of the VP with a dose 20% lower than minimal erythema dose (MED) calculated by the operator before the session (4). The length of each session depends on the length of the single light spot and the extension of the VP areas (4). The subjects are treated with the following scheme: five sessions, one a day for 5 consecutive days;10 days break; one session every 15 days for 5 months (4). After 5 months five subjects responded with more than 75% repigmentation (three achieved 100% repigmentation), two individuals showed 50-75% repigmentation and one showed repigmentation in less then 50% of the area treated. No pain or burning or itching sensations were reported by the subjects. The average cumulative UV-B dose with the treatment was 5.025 J/cm2 (range 2.4-6 J/cm2) per subject (4).

Finally it has been observed that only well-motivated, highly compliant patients are suitable for Photoradiation. Follow-up studies are needed to ascertain whether the repigmentation induced by this limited irradiation method is permanent (4).




Vitiligo patients present lower plasma levels

of α-melanotropin immunoreactivities

Vitiligo is a depigmenting disorder characterized by the development of white patches with evidence in favour of an autoimmune mechanism [1,2,3,4,5,6] (5). We investigated the role of melanotropins and the plasma levels of a-melanotropin and ACTH-like immunoreactivities

in 40 vitiligo patients with the aim of detecting a possible influence of neuropeptide regulation of immunity (5).

Melanocytes via the activation of the melanocortin-1 receptor to melanin production (5). Melanotropins exert both paracrine and autocrine functions in human skin, but the neuropeptide a-MSH is also involved in host defense and acts as a modulator of cutaneous inflammation (5). The activation of the transcription factor NF-j-B appears to be a crucial event in immune and inflammatory responses (5). Data suggest that a-MSH appears to function as a general inhibitor of NF-j-B activation (5). a-MSH has the potential to suppress T cell-mediated inflammation and to regulate lymphokine production by effector T cells[3,5] (5).

Morning blood samples were collected from 32 women and 8 men throughout January to December 2002 (5). 21 patients had active and 19 had stable vitiligo disease (5). All patients were suffering from nonsegmental vitiligo at different stages of the disease. Sixteen persons presented with an additional autoimmune thyroid disease (5).

a-MSH was measured in human plasma by the EURIA-a-MSH radioimmunoassay provided by EURO-DIAGNOSTICA AB (5). In order to increase the sensitivity of the assay, a sequential assay with delayed additions of 125-I- a-MSH is performed (5). Antibody-bound 125-I-a-MSH is separated from the free fraction using the double antibody polyethylene glycol precipitation technique (5). The radioactivity of the precipitates is measured.

Median a-MSH levels in vitiligo patients were 6.4 pmol/l and significantly lower (p = .01) than in control persons with 11.4 pmol/l (Table 1). We also investigated the subgroups with active (N = 21) and stable (N = 19) vitiligo. Patients with active disease had median plasma a-MSH levels of 6.7 pmol/l and patients with stable lesions had median plasma a-MSH levels of 5.9 pmol/l (5). We also analysed the subgroups of patients with an additional autoimmune disease (N = 16) and the patients without (N = 24) (5). The median a-MSH levels were 6.9 pmol/l in the first and 6.0 in the latter subgroup (5).



Table 1

Test statistics for a-MSH, ACTH and cortisol (Mann–Whitney-

Wilcoxon U-test)

____________________________________________________

Test statistics a-MSH ACTH Cortisol

____________________________________________________

Mann–Whitney U 483.000 500.500 692.000

Wilcoxon W 1303.000 1361.500 1553.000

Z -3.184 -3.021 -1.211

Asymp. Sig. (2-tailed) 0.001 0.003 0.226



Fig. 1. a-MSH plasma values (pg/ml) in patients and control group.



a-MSH down-regulates the production of proinflammatory and immunomodulating cytokines including IL-1, IL-6 and TNF-a (Figure 1) (5). It has been shown that concentrations of a-MSH are reduced in the epidermis of vitiligo patients which could contribute to the pathogenesis of vitiligo. It is not clear where this plasma

a-MSH immunoreactivity originates, possibly in the pituitary but also other tissue, e.g., the skin (5). We also do not know what quantity of epidermal cells contribute to systemic levels of a-MSH in physiological or pathological conditions (5).



Fig. 2. a-MSH plasma values (pg/ml) in patients



Fig. 3. a-MSH plasma values (pg/ml) in control persons.



Lower a-MSH plasma levels seem to be related to vitiligo. This observation was found independently of disease activity and further association with autoimmune disease[3,5] (5). Lower plasma a-MSH levels might represent an immuno-endocrine condition with higher susceptibility for the development of autoimmune depigmentation (Figure 2, Figure 3) (5). This would be in accordance with the concept that a-MSH induces the activity of regulatory T cells, might suppress autoimmune disease and could be applied to create or reestablish tolerance to prevent autoimmune disease (Figure 2, Figure 3) (5). Considering the important association of vitiligo with other autoimmune disorders and endocrinopathies and the known implication of a-MSH in immune modulation, further investigation of its role in disease development is encouraged (5).

Identification of autoantibody to melanocytes

and characterization of vitiligo antigen in vitiligo

patients

The etiology of vitiligo is unknown, but there are several hypotheses that have been put forward. Among these hypotheses the autoimmune theory is the most popular one explaining the pathogenesis of vitiligo[1,4,5,6] (6). It was first suggested after the clinical observation that vitiligo

occurred concurrently with autoimmune thyroid diseases, pernicious anemia, and others [1,4,5,6] (6). Studies of the autoimmune theory have begun to show results; Naughton et al., using immunofluorescence and immunoprecipitation, have demonstrated the presence of anti-melanocyte antibody reacting with melanocyte surface antigen in vitiligo patients (6). This study was conducted to identify and characterize the vitiligo antigens defined by antibodies in patients with vitiligo, and to examine their specificity and changes of antibodies after treatment using immunofluorescence, ELISA and immunoblotting analysis (6).

Sera were collected from 18 randomly selected patients with vitiligo, 18 with Behcet’s disease, 22 with syphilis, and 14 healthy matched control subjects (6). Melanocytes were isolated from uninvolved skin of vitiligo patients and from normal skin of control subjects. Melanocytes isolated from foreskin and skin biopsy, were cultured.

Reactions to melanocytes: In the reaction with normal melanocytes, there was a statistically significant difference between normal (n = 14) and vitiligo sera (n = 18): 0.34 _+ 0.08 for vitiligo sera and 0.16 f 0.04 for normal sera (6). The similar results were observed on the vitiligo melanocytes: 0.38 + 0.05 for vitiligo sera and 0.15 + 0.03 for normal sera (6). The change after systemic steroid treatment. In order to find out what effect steroids had on the

titers of autoantibodies, prednisolone, IO-20 mg (0.3 mg/kg), was given for 4 months to 10 vitiligo patients, with serum collection before and after steroid treatment (6). Using live cell ELISA, the changes in optical density were evaluated before and after treatment (6). Eight (80%) of the 10 patients showed decreased optical density after treatment, and the result is statistically significant by paired t-test (6).

The findings in this study indicated that immunofluorescent stain of melanocytes showed strong fluorescence when reacted with vitiligo sera, support the presence of autoantibody reacting with melanocytes in vitiligo serum. In live cell ELISA which was used to prevent reaction between vitiligo sera and cytoplasmic antigen, vitiligo sera showed higher optical density than normal sera, and the reaction was blocked by pretreatment with rabbit antimelanocytic antibody (6). It can be interpreted that the high optical density found in vitiligo sera is the result of specific reaction between autoantibody in vitiligo sera and surface antigen of melanocytes (6). However, it is confusing that vitiligo sera showed increased optical density in reacting with fibroblasts, although there is one previous study that found autoantibodies in vitiligo patients (6). Our finding that the correlation between clinical improvement by systemic steroid therapy and decreasing level of autoantibody to melanocytes, also supports the hypothesis that autoantibodies play a role in pathogenesis of vitiligo. We suggest that the sera of vitiligo patients have autoantibodies mostly directed to the 65-kDa melanocyte surface antigen and that this antigen may play a role in the development or improvement of vitiligo[5,6] (6).



______________________________________________________________________________

Conclusion:

The expression of genes of the melanocortin system is altered in vitiligo. Decreased expression of the genes of the melanocortin system , enzymes of melanogenisis and systematic levels of a-MSH in the lesional skin was demonstrated in these studies (3), (5). POMC (proopiomelanocortin) expression was lower in lesional skin compared to non-lesional skin (3). Expression of melanocortin receptors was increased in unaffected skin of vitiligo patients compared to healthy subjects and decreased in lesional skin compared to uninvolved skin of vitiligo patients, the differences were statistically significant in the cases of MC1R (melanocortin receptor 1) and MC4R (melanocortin receptor 4). Further studies using histochemical methods must be conducted to localize MC3R expression to distinct cell types in the skin (2).

The autoimmune hypothesis is best supported because of the numerous genetic association and genetic linkage studies, in combination with humoral and cellular immune aberrancies(1). The neurohumoral, cytotoxic, and oxidative stress theories have moderate evidence. Newer theories, such as melanocytorrhagy and decreased melanocyte survival, are just beginning to accrue data (1). Because all of these theories are plausible, it seems likely that vitiligo may indeed include a spectrum of disorders that manifest as a common phenotype.




Citations

1) Alikhan, A. et al. (2011). Vitiligo: A comprehensive overview: Part I. Introduction, epidemiology, quality of life, diagnosis, differential diagnosis, associations, histopathology, etiology, and work-up. Journal of the American Academy of Dermatology, 65(3), 473-491.

2) Felsten, L. et al. (2011). Vitiligo: A comprehensive overview: Part II: Treatment options and approach to treatment. Journal of the American Academy of Dermatology, 65(3), 493- 500.

3) Kingo, K. et al. (2007). Gene expression analysis of melanocortin system in vitiligo. Journal of dermatological science, 48(2), 113-122.

4) Lotti, T. et al. (1999). UV-B radiation microphototherapy. An elective treatment for segmental

vitiligo. Journal of the European Academy of Dermatology and Venereology, 13(2), 102-108.



5) Pichler, R. et al. (2006). Vitiligo patients present lower plasma levels of α-melanotropin immunoreactivities. Neuropeptides, 40(3), 177-184.

6) Park, Y. et al. (1996). Identification of autoantibody to melanocytes and characterization of vitiligo antigen in vitiligo patients. Journal of dermatological science, 11(2), 111-121.

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