Segmental vitiligo is unique and distinct in several ways. We tried to characterize the pattern; to evaluate the efficacy of medical treatment; to measure the surrogate auto-antibodies and developed criteria to differentiate from focal non-segmental vitiligo.
Characterizing the pattern: In 188 patients the mean age at onset was 12 years The mean duration of disease was 4.24 years. 36 patients had mixed vitiligo. Most patients (170, 90.4%) had only 1 segment involved, while 17 (9%) had 2 and 1 (0.5%) had 3 segments involved. The head and neck was the initial site of onset in 98 patients. Definite blaschkoid pattern was observed in 93 patients, dermatomal in 6, phylloid in 2, checkerboard in 1 and Voigt’s lines in 1.
The body surface area involvement varied from less than 1% to 8% and was 1% or less in 64.3% patients. Leucotrichia was present in 162 (86.1%) patients. Normally pigmented skin beyond the margin of segmental vitiligo also showed leucotrichia in 122 (64.8%) patients. The margins of the lesion were completely irregular in 77 (40.9%), partly irregular and partly smooth in 84 (44.6%) patients and completely smooth margins in 27 (14.36%).
Therapeutic efficacy of two topical agents, In a randomized non-blinded controlled study on 60 consecutive patients of segmental vitiligo, 31 received 0.1% tacrolimus ointment twice daily and 29 received 0.05% fluticasone propionate cream once daily for 6 months. At the end of 6 months, median repigmentation rate was 15% in tacrolimus group and 5% in fluticasone propionate group. Thus, tacrolimus is statistically not better than fluticasone propionate and both the drugs produce unacceptable repigmentation.
Presence of auto-antibodies by using surrogate markers: In 101 patients with vitiligo (45 segmental, 50 non-segmental and 6 mixed) ANA was positive in 8 out of total 48 patients with non-segmental vitiligo as compared to 2 out of 51 in segmental vitiligo. This was statistically significant. TPO was done in 38 segmental and 38 non-segmental vitiligo patients and was positive in 2 and 7 respectively, which was statistically insignificant. It seems that auto-immunity has very little role.
Validation of clinical criteria to diagnose segmental vitiligo
Based on the clinical features of segmental vitiligo, essential and minor criteria were decided and then study was done to validate these criteria by comparing patients’ diagnosis by 3 experts in the field. In this study so far, consensual expert opinion (by 3 experts) is available for 70 cases. Amongst them, 50 cases are reported as segmental vitiligo by experts and also fulfilled criteria.. Similarly, 7 cases are reported as non-segmental by experts and our criteria both.
Conclusion
By applying certain criteria, early diagnosis and differentiation from non-segmental vitiligo is possible. It is the “first cousin” of vitiligo, but having several distinct features morphologically, having poor response to medical therapy and less of auto-immunity. Its predominant blaschkoid pattern suggests mosaicism and approach to manage it may require a paradigm shift.