SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
VOLUME 8 NUMBER 1 • MARCH 2011
5
Vitiligo
BB ADAMJEE
V
itiligo is an acquired, idiopathic condition characterised
by well-circumscribed flat, non-palpable areas (macules)
of total loss of melanin pigment (depigmentation).
1
This depigmented skin is functionally different from normally
pigmented skin. It does not react normally to contact sensitisation
or to contact allergens and while normal white skin is prone to skin
cancers, skin with vitiligo is generally resistant to carcinogenesis of
keratinocytic origin. It is not susceptible to melanomas, due to the
absence of melanocytes. By contrast, skin in albinism is susceptible
to squamous cell carcinomas and rarely melanomas.
2
Vitiligo affects approximately 0.5 to 2%of the general population
and may appear from after birth to senescence.
1
Peak age of onset
is between 10 and 30 years. Both genders are probably equally
affected, but the female predominance in some studies is likely
attributable to concern about a cosmetic problem.
3
Pathogenesis
Vitiligo is a multifactorial disease involving genetic and non-genetic
factors. Between 30 and 40% of patients have a positive family
history. Inheritance may be polygenic or autosomal dominant
with variable penetrance. Segmental vitiligo is not familial. Many
theories have been proposed regarding aetiology.
1,4,5
Autoimmune hypothesis
This theory proposes that altered humoral or cellular immunity
results in the destruction of the melanocytes. Dysfunction of the
humoral immunity is supported by the association of vitiligo with
autoimmune endocrinopathies. These disorders are accompanied
by circulating anti-organ antibodies. Organ-specific antibodies to
thyroid and gastric parietal cells, and adrenal tissue are found more
frequently in people with vitiligo than in the general population.
Disorders associated with vitiligo
4
(*auto-antibodies
demonstrable):
• thyroid disease* (hyperthyroidism and hypothyroidism)
• pernicious anaemia*
• Addison’s disease*
• diabetes mellitus*
• hypoparathyroidism*
• myasthenia gravis*
• alopecia areata
• morphoea and lichen sclerosus
• halo naevus*
• malignant melanoma.*
A complement-fixing antibody to melanocytes has been found
in the sera of patients with alopecia areata, mucocutaneous
candidiasis and multiple endocrine insufficiencies, in addition
to vitiligo. These antibodies are directed against melanocyte
antigens such as tyrosinase and tyrosinase-related proteins 1 and
2 (TYRP1 and TYRP2). Recently, two transcription factors SOX9
and SOX10, and the melanin-concentrating hormone receptor-1
have been identified as auto-antigens in patients with autoimmune
polyendocrine syndrome type I and with idiopathic vitiligo.
Evidence favouring the involvement of cellular immunity is
also strong. The T cells that infiltrate perilesional epidermis are
predominantly CD
8
+
T cells, which express cutaneous lymphocyte-
associated antigen (CLA) and the interleukin-2 (IL-2) receptor. These
CLA
+
T cells are found primarily near disappearing melanocytes
and many express perforin and granzyme B. Focal expression of
intercellular adhesion molecule-1 (ICAM-1) and HLA-DR occurs
within the epidermis at sites of interaction between immune
infiltrates and disappearing melanocytes. Skin-homing T cells
therefore play an important role in melanocyte death.
Reduced serum-transforming growth factor-
β
levels have been
observed and this may contribute to enhanced cellular immunity.
Diminished maturation of regulatory T cells may lead to impaired
inhibition of inflammation.
6
Skin-homing melanocyte-specific cytotoxic T lymphocytes (CTLs)
are often detected in the blood of patients with autoimmune
vitiligo, implicating their involvement in the melanocyte destruction.
Intrinsic defect of melanocytes
An abnormal structure of the rough endoplasmic reticulum of
vitiligo melanocytes may play a role in the development of vitiligo.
Defective free radical defence(s)
A metabolic defect in biopterin metabolism results in hydrogen
peroxide (H
2
O
2
) overproduction. Accumulation of H
2
O
2
in the
Correspondence to: Dr BB Adamjee
Department of Dermatology, University of the Free State and Universitas
Academic Health Complex, Bloemfontein.
Tel: +27 0(51) 405-2546
e-mail:
S Afr J Diabetes Vasc Dis
2011;
8
: 5–9.
BB Adamjee
