The epidemiology and genetics of vitiligo

Commonly it is stated that about 1% of the world’s population has vitiligo vulgaris and that this prevalence is constant for all ethnic groups in all countries; however, the extant data do not confirm these assumptions. Several large studies have been done in Denmark and in India that suggest the prevalence is much lower than frequently purported. In 1973, an investigator reported the results of an extensive survey of both urban and rural populations in or around the city of Surat, India.1 He and his colleagues examined 1887 rural inhabitants and 7178 residents of the city. These ascertainment groups represent about 60% of the population of the area. He observed that vitiligo vulgaris affected 0.49% (1 per 212 individuals) in the rural areas. The prevalence was higher in the urban areas. He found that 1.78% or 1 per 56 individuals within the city of Surat had vitiligo. Men and women were equally affected, although members of certain castes or tribes had higher or lower prevalence rates than the population at large. Some castes had no affected members, others as many as 3.6%. Kinships tended to express a vitiligo trait, so that often two or three members of the primary kinship (parents, siblings and children) were affected; however the familial patterns did not conform to any obvious Mendelian trait. ’ Another investigator studied 15,865 individuals in Calcutta, India drawn from the general population.2 He found the general prevalence of vitiligo in Calcutta to be 5 per 1000 population, or 0.2%. From those with vitiligo in this group, he ascertained additional pedigree data on the familial patterns of vitiligo. He found additional 270 individuals with vitiligo in the families of the probands in the original study group. Both sexes were equally affected. There was a 4-5 fold increased prevalence of vitiligo within close biological relatives of probands with vitiligo, compared to the population at large.2 In Denmark an investigator surveyed 47,033 Danish individuals for vitiligo vulgaris. He ascertained his subjects by examining medical records, autopsy and hospital charts, and newspaper advertisements. He found that 0.38%, or 1 per 263 individuals, had vitiligo. Both sexes were equally affected. Before the age of 10 years only 0.09% of the population was affected; but the prevalence was maximum by age 60 vears, at which time 0.9% of individuals were affected.‘? From these studies, it seems reasonable to conclude that the general prevalence of vitiligo vulgaris throughout the world is about 1 per 200 individuals, and that both sexes are affected equally; however it should be noted that there are locations in the world, such as isolated villages in India, where the prevalence can be much higher, as high as 8%.-2 The most obvious explanation for this uneven distribution of vitiligo is inheritance of the disease; however there are workers who are exposed to chemicals that cause them to develop occupational depigmentation that resembles vitiligo.5 It is possible, especially in underdeveloped countries such as India that are burdened by a caste system, that the higher than expected prevalence is related to environmental factors or, more likely, to a combination of genetic and environmental factors.