7 Segmental Vitiligo

Vitiligo is largely classified into segmental and non-segmental types (Table 1).1 This classification is based on the original report by Koga in 1977.2 Koga proposed that vitiligo in a non-dermatomal distribution be referred to as Type A and vitiligo in a dermatomal distribution be Type B, the latter of which corresponds to what is known today as segmental vitiligo (SV). Since then, the distinctive characteristics of SV have been described.3-6 Recently, it was proposed that vitiligo be classified into four major types: segmental, nonsegmental, mixed, and unclassified.7 The incidence of SV is not well-established because different investigators report variable percentages of patients having SV. El-Mofty et al reported that only 5% of patients with vitiligo had the segmental type.8 Koga and Tango described that in their population, 27.9% had SV.3 Several studies in Korea revealed the prevalence of SV to range from 5.5% to 29.6%.4,9,10 The typical lesion of SV is not significantly different from that of NSV. Both can initially appear as focal vitiligo, which involves a small area.11 However, SV has a distinct natural history and unique clinical features.1,3,4 In addition, SV shows different therapeutic characteristics when compared with NSV.1,12 SV can appear at any age, but the majority of cases occur early in life between the ages of 5 and 30 years old. Koga and Tango reported that 82% of type B vitiligo (SV) patients noticed their first depigmented patches before the age of 30.3 In the pivotal SV study by Hann and Lee, the mean age of onset was 15.6 years, and SV developed before 10 years of age in 41% of cases, and before 30 years of age in 87%.4 In our study, the mean age of onset was 19.8 years; 32% of SV started before 10 years of age and 62% before 20 years of age.6 SV typically presents with unilateral involvement of depigmented macules surrounded by normal skin. The color of the macules is usually white and more distinguishable with Wood’s light examination. However, macules may have a more irregular border and less homogeneous pattern of pigment loss than NSV.11 Trichrome vitiligo, which is characterized by both depigmented and hypopigmented macules, is reported in SV.13 SV shows a quasi-dermatomal mode of distribution, but seems to be different from the pattern of herpes zoster. SV often involves a segment that includes the parts of several dermatomes and may at times, go over the midline partially. Some cases may involve lines or large bands consistent with Blaschko’s lines.14,15 There is no preferential distribution between right and left sides of the body. Very rarely, SV involves two or more different segments with ipsilateral or contralateral distribution. Lee and Hann reported that 5 of 240 SV cases showed bilateral SV on the same or different dermatomes that appeared on both sides of the body.16