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Vitiligo
1. DEFINITION
An area of acquired cutaneous depigmentation characterized by well-circumscribed milky white macules devoid of identifiable melanocytes.
2. AETIOLOGICAL HYPOTHESES
Various theories are suggested for the aetiology of vitiligo; the same mechanism may not apply to all cases.
2.1 Autoimmune Hypothesis
Autoimmune destruction of cutaneous melanocytes with total loss of melanocytes and melanin pigment in the skin of the affected area. Lymphocytic infiltration on skin biopsy indicate lymphocytes are involved in the destruction process.
Frequently associated with other Autoimmune diseases such as alopecia areata, autoimmune thyroid disorders, Addisons adrenal disease, atrophic gastritis and pernicious anaemia, diabetes
Serum autoimmune antibodies against melanocyte, thyroid, adrenal, islet cell, gastric parietal cell and intrinsic factor have been demonstrated.
2.2 Neurogenic Hypothesis
A compound is released at peripheral nerve endings in the skin which is toxic to melanocytes and inhibits melanogenesis. It is postulated that in the dermatomal variant, the affected area shows sympathetic nerve dysfunction. Catechol neurotransmitters probably destroy the melanocytes instead. There is little support for this hypothesis.
2.3 Self-destruct Theory of Lerner
Defect of a natural protective mechanism in melanin synthesis within melanocytes, leading to accumulation of toxic precursors (phenolic compounds) which destroy melanocytes. This hypothesis is based on the lethal effects produced by chemical compounds (phenols) on functional melanocytes; the resulting leukoderma is indistinguishable from idiopathic vitiligo.
3. CLINICAL PRESENTATION
Affects around 1% of the population in all races, but more troublesome in dark skin where there's marked contrast between normal and depigmented areas. Hence the incidence may be apparently higher in pigmented races where the social impact is also greater. Family history of the condition is found in one third of the affected patients. Sex ratio is equal. Half the patients first present before 20 years old. It may be precipitated by injury or sunburn. In light skin individuals, vitiligo may only be discernible in summer, when the vitiliginous area becomes sunburnt. The main symptom being cosmetic and presents when the patient notices that the affected area fails to tan after sun exposure unlike the surrounding normal skin. It is a essentially a clinical diagnosis - based on the morphology and distribution of lesions as well as the exclusion of other hypopigmented skin lesions.
Vitiligo may rarely be associated with premature greyness of hair, retinal pigmentary loss, uveitis, deafness, CNS involvement (Vogt-Koyanagi syndrome). Other associations include : halo naevus, malignant melanoma, alopecia areata, autoimmune thyroid disorders, Addisons adrenal disease, chronic atrophic gastritis, Pernicious anaemia and diabetes mellitus.
4. DIAGNOSTIC HALLMARKS
4.1 Distribution
Localised sunexposed areas such as dorsal surface of hands and the face, including peri-orificial and peri-orbital areas. Hyperpigmented areas such as Axilla, Groin, Genitalia, flexures, nipple. Sites of friction and bony prominences like elbows and knees.
Generalised - Widespread
Unilateral Variant - unilateral segmental pattern seen in children occurs (linear/dermatomal) occasionally
4.2 Individual Lesion
(a) Sharp Margination
(b) No Scale
(c) Normal texture and intact sensation.
(d) Typical - milk-white colour
(e) Atypical
Trichrome vitiligo
- an intermediate uniform tan colour
- naturally evolves to a typical vitiligo macule
Quadrichrome vitiligo
- macular perifollicular or marginal hyperpigmentation seen in repigmenting vitiligo
Inflammatory vitiligo
- erythematous, raised border similar to that seen in tinea versicolor.
5. TREATMENT
Educate and encourage relatives, friends and society to overcome the stigma that this is not an infectious disease like leprosy.
Acceptance of patient by physicians setting an example (e.g. shaking hands) should be supportive to patient and help to overcome stigma.
Reassurance that this is a cosmetic problem and does not affect the patient's health directly.
Educate the patient about the nature of the disease, that treatment may be difficult and prolonged, and the results may not be predictable. While the patient should not have unrealistic expectations they need not be discouraged. More important is to take good care of their own skin, concentrate on what can be done even if the condition can not be cured at present.
(i) Sunscreens (SPF 15-30)
These are recommended for three reasons : 1) area of vitiligo are more susceptible to sunburn. 2) sunburn injury can extend the depigmentation (Koebner response). 3) Sun-induced darkening of the surrounding normal skin causes accentuation of the cosmetic disfigurement. Sunscreens which shield both UVB and UVA light should be used.
For the same reason, avoiding outdoor activities under the strong mid-day sun, together with protective clothing, will reduce ultraviolet damage to depigmented skin which is devoid of protective melanin.
(ii) Camouflage Cosmetics (Covermark, Dermablend etc.)
Covermark and Dermablend are cosmetics that can be used to match most skin hues.
Quick-tanning preparations containing dihydroxyacetone may be used to tan the vitiligo a more acceptable colour. It can produce different shades. Instructions and guidance from a cosmetic instructor are required to give the best cosmetic results and safety. These preparations are especially useful on the eyelids where potent topical corticosteroids and ultra-violet light should not be used.
(iii) Repigmentation therapies
Moderately potent to potent topical corticosteriods
e.g. Sicorten Cream (0.5% halometasone)
This may be applied to affected area twice daily as a trial. Therapy should be discontinued if repigmentation has not begun after six to twelve months. The patient need to be seen every 1-2 months to check for signs of cutaneous atrophy from treatment. Caution is needed when applying it to the face and flexures (once daily/alternate day). It should not be applied to eyelids and periorbital areas to avoid the risk of steroid-induced glaucoma and cataract.
PUVA therapy - Topical or systemic (Refer to chapter 17)
Topical PUVA involves Ultra-violet A irradiation 30 minutes after application of meladinine (topical methoxasalen) to the localised vitiliginous area. Systemic PUVA involves ingestion of methoxasalen (0.6 mg/kg) two hours before irradiation.
Treatment should be attempted under the supervision of a dermatologist or those experienced in its use. In inexperienced hands, PUVA may carry the risk of phototoxic reaction, ocular damage etc.
Careful patient selection is also required. Within the Social Hygiene Service, predominantly facial lesions (except eyelids) of recent onset are considered for PUVA, because they tend to give better results. Some degree of repigmentation occurs in 50-75% of cases compared with 15-20% in controls.
The patient undergoes treatment 2 times per week, and needs to avoid sunlight for 2 days after each treatment, using sunscreens both indoor and outdoor. It takes at least 2-3 months to begin having an effect and therapy needs to be continued for at least one year (100-200 treatment sessions) before maximum benefit is reached. Hence a long term commitment to therapy is required, and this must be appreciated by the patient before embarking on therapy. The physician also needs to take into consideration the patients' age, sex and disease severity; medical, social, occupational and psychological factors.
If perifollicular pigmentation has not appeared after three months of therapy, it is unlikely to occur; treatment might as well be stopped. But once repigmentation has begun, it tends to persist and spread with continuous treatment. However complete repigmentation occurs in 15-20% only.
Systemic PUVA is less often used than topical PUVA in vitiligo.
Contra-indications for systemic PUVA include :
pregnancy, children <12-year old, photosensitivity;
Cardiac, hepatic and renal disease; Aphakia and cataracts,
history of skin cancers
(iv) Depigmentation therapies using bleaching agents such as 20% Monobenzyl ether of hydroquinone (Benzoquin 20% cream) once or twice daily is indicated when vitiligo is extensive >50% involvement or near universal. Benzoquin may cause a contact dermatitis; hence as a test before generalized therapy, it should be applied to a single pigmented spot daily for 1 week. Thereafter large pigmented areas are treated twice daily for up to 6 months. The compound is cytotoxic to melanocytes and destroys them. This process which removes pigment from the remaining normal skin is irreversible. The skin becomes albinoid, but the cosmetic appearance is improved substantially. The patient must remember they are sun-sensitive and need protective sunscreen.
Experimental Repigmentation modalities :
These can be tried in stationary vitiligo which are not extending any further. They have achieved variable success in different individuals.
Grafts from uninvolved skin containing viable melanocytes; punch minigrafting using autologous pigmented donor sites is the simplest, least invasive surgical approach. Alternatives include growing in vitro melanocytes from the patients' normal skin and injecting them into artificially induced blister cavities in the depigmented areas. Repigmentation by tattooing has also been tried with some success.
6. COURSE AND PROGNOSIS
Variable and somewhat unpredictable. May remain static, spread or repigment. But usually the condition is gradually progressive, sometimes extending rapidly over a period of several months and then remaining quiescent for many years. Spontaneous repigmentation is noted in about 10-20% of patients.
Factors indicating good prognosis for repigmentation are :
Recent onset <6 months, in a young individual on the facial area.
Conversely factors which indicate an unfavourable prognosis are :
Late onset in life, long-standing persistent lesions, on the extremities and on the lips.
Repigmentation begins within the affected area from the hair follicles where there may be residual melanocytes; or else they occur from the normal pigmented skin immediately adjacent to the vitiliginous area. Once repigmentation begins it tends to continue, albeit slowly and sometimes trivial.
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