Segmental vitiligo and the classification of vitiligo
Segmental vitiligo, is characterized by a unilateral and localised distribution of vitiligo patches. Dr van Geel and collaborators have looked at this type of vitiligo (see British Journal of Dermatology 2013; 168: 56-64). So far, the underlying mechanism is still an enigma.
In order to obtain an insight into the causes of segmental vitiligo, the researchers compared its distribution pattern with those of skin conditions with a possible mosaic or neurogenic background. (Mosaicism is a condition in which cells within the same person have a different genetic makeup). The results showed that the distribution pattern of segmental vitiligo is not entirely similar to any other skin condition, although some mosaic skin disorders have more overlap with segmental vitiligo than others. Dr van Geel and colleagues concluded that cutaneous mosaicism may be involved in segmental vitiligo.
Experts have looked at how vitiligo is classified (Ezzedine et al. in Pigment Cell and Melanoma Research 2012; 25: E1-13). They concluded that segmental vitiligo be classified separately from all other forms of vitiligo and that the term ‘vitiligo’ be used as an umbrella term for all non-segmental forms of vitiligo; this includes ‘mixed vitiligo’ in which segmental and non-segmental vitiligo are combined and which is considered a subgroup of vitiligo. The experts recommended that disease stability be best assessed based on the stability of individual lesions rather than the overall stability of the condition, as the latter is difficult to define.