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. 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 an essentially clinical diagnosis, based on the morphology and distribution of the lesions as well as the exclusion of other hypopigmented skin lesions.