Halo-Like Disappearance of Café au Lait Spot: A Clue for the Role of Autoimmunity and Somatic Mosaicism in Segmental Vitiligo

Abstract

Vitiligo, an autoimmune skin disease, is primarily driven by interferon- γ -CXCL10 signaling involving autoreactive CD8+ T cells targeting melanocytes. Although the pathogenesis of segmental vitiligo remains unclear, recent insights suggest neural, somatic mosaicism, and microvascular mechanisms as possible explanations. Here, we present a case of a 5-year-old boy with a cafe au lait macule that transformed into a hypopigmented patch, suggestive of segmental vitiligo. Biopsies showed early vitiligo features in the hypopigmented area, where there was high prevalence of CD8+ T cells, accompanied by CXCL10 expression. Growing evidence supports the autoimmune basis and cutaneous mosaicism in segmental vitiligo, with this case highlighting the role of vulnerable melanocytes, autoimmune attack, and the abrupt loss of repigmentation post-treatment. This case adds weight to the autoimmune and mosaicism theories in segmental vitiligo pathogenesis.