Vitiligo is a polygenic and multifactorial disorder, reflecting the simultaneous contributions of multiple genetic risk factors and environmental triggers.
Large-scale studies, mainly in whites of European descent and in Chinese, have found about 50 different genes. These genes contribute to the risk of vitiligo and also to other autoimmune diseases.
A large number of these genes are involved in immune regulation, many others play a role in cell apoptosis (programmed cell death), and still others are involved in the regulatory functions of melanocytes.
For the latter group, there appears to be an opposite relationship between susceptibility to vitiligo and susceptibility to melanoma. This suggests that vitiligo can activate a normal immune surveillance mechanism for melanoma.
While many of the specific biological mechanisms through which these genetic factors operate to cause Vitiligo remain to be elucidated.
Vitiligo and genetic correlation
The genetic basis of vitiligo is strongly intertwined with the genetic basis of other autoimmune diseases with which vitiligo is epidemiologically associated.
Indeed, the first clue to the autoimmune origin of vitiligo came in the original 1855 report of Addison’s disease.
It included a patient with idiopathic adrenal insufficiency, generalized vitiligo and pernicious anemia, a concomitant of autoimmune diseases that suggested etiological factors.
Subsequently, the concomitance of several autoimmune diseases, including vitiligo, was reported by many researchers, and the key combinations of concomitant autoimmune diseases were subsequently coded.
Numerous researchers have documented the correlation of vitiligo with various other autoimmune diseases.
In particular:
- autoimmune thyroid disease
- pernicious anemia
- Addison’s disease
- systemic lupus erythematosus
- rheumatoid arthritis
- type 1 diabetes mellitus
- adult onset and possibly psoriasis
Of particular importance, these same autoimmune diseases associated with vitiligo also occur with greater frequency in first-degree relatives of vitiligo probands who do not have vitiligo.
Thus indicating that these autoimmune diseases share at least some of their genetic basis with vitiligo.
Vitiligo and Genetics Studies
Vitiligo disorder was first described by Claude Nicolas Le Cat in 1765.
However, the first specific consideration of a genetic component in vitiligo does not come until 1950, when Stűttgen and Teindel reported a genetic factor in eight families with multiple relatives with vitiligo.
Stűttgen noted that in his family, vitiligo appeared to show dominant inheritance.
After intermarrying with a family with apparent recessive thyroid disease, she encountered early Vitiligo.
This finding would now be regarded as complex inheritance.
Other scientists subsequently reported symptoms of vitiligo in pairs of homozygous twins, indicating an important role for genetic factors.
The first series of clinical cases reported a frequency of vitiligo in the relatives of the first individuals examined from 11 to 38%.
This highlighted the importance of genetic factors even in typical cases of vitiligo.
However, genetic studies on vitiligo came much later.
Hafez and Das suggested a polygenic and multifactorial mode of inheritance and estimated the inheritance of vitiligo to be 46% to 72%.
Subsequent investigations also supported a polygenic and multifactorial model, with heritability of about 50%.
A twin study of vitiligo in whites of European descent reported that the concordance of vitiligo was 23% in monozygotic twins, underlining the importance of non-genetic factors and genetic factors in the pathology of vitiligo.
In this same study, large-scale genetic epidemiological analyzes showed that in whites of European descent, the overall frequency of vitiligo in first-degree relatives of probands was 7%.
