Segmental Vitiligo L80.-

Segmental vitiligo (SV) is a variant of vitiligo characterized by its early onset and rapid stabilization. The time-limited progression period is 6 to 24 months, while non-segmental vitiligo (NSV) is chronic, possibly with an uncertain lifelong course.

The clinical picture is usually unilateral. Bilaterality has rarely been described. Observational studies on the distribution pattern indicate that the originally stated dermatomal classification is a misinterpretation and classify the distribution pattern as a cutaneous mosaic. In contrast to NSC, the melanocytes of the hair follicles are affected early in SV, so that up to 50 % of patients with segmental vitiligo show poliosis in the lesional areas. The prevalence of concomitant autoimmune diseases (e.g. thyroiditis) is lower in segmental vitiligo (SV) than in non-segmental vitiligo (NSV).

With regard to their pathophysiology, there appear to be differences between segmental and non-segmental vitiligo. For example, serum levels of TWEAK (Tumor Necrosis Factor-like Weak inducer of Apoptosis) were significantly higher in SV patients compared to NSC patients. In addition, TWEAK was found to be a biomarker with a sensitivity of 100 % and a specificity of 80.1 % in differentiating between SV and NSC (El-Taweel AEI et al. 2021). The ROC (Receiver Operating Characteristic) analysis showed that TWEAK had a sensitivity of 80% and a specificity of 56.67% in the diagnosis of vitiligo and a 100% sensitivity and 80.09% specificity in distinguishing segmental from non-segmental vitiligo (El-Taweel AEI et al. 2021).

The mean age at first manifestation of segmental vitiligo is 16 years, on average 8 to 10 years earlier than the mean age of onset of non-segmental vitiligo. Extensive involvement of segmental vitiligo lesions on the trunk and extremities was observed significantly more frequently in patients with a lower age of onset.

Immunohistochemical data on segmental vitiligo are rather sparse. Significant lymphocytic infiltrates have only occasionally been observed.

SV and NSC differ in terms of response to treatment: in general, SV patients respond poorly to phototherapy compared to NSC, possibly due to earlier depletion of the follicular reservoir in SV. In contrast, SV patients have an excellent and long-term response to melanocyte-keratinocyte transplants. This behavior indicates a genetic defect in lesional melanocytes, but not in non-lesional melanocytes.

The localized and unique distribution pattern of SV is suggestive of somatic mosaicism. This places SV in a category of similar diseases such as lichen striatus, blaschkitis, linear lupus erythematosus and linear circumscribed scleroderma, in which autoimmunologic mechanisms are also suspected. All of these diseases are characterized by a young age of onset, transient disease activity with spontaneous resolution and a limited response to treatment.

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