CPC14 Blaschko-Linear Trichoepitheliomas: Unveiling Type 1 Segmental Mosaicism

The document describes a case of a 7-year-old boy with multiple trichoepitheliomas in a Blaschko-linear pattern on his face, which is a rare presentation. These benign tumors, which showed follicular differentiation, were present at birth and increased over time. The boy's condition was diagnosed as segmental trichoepitheliomas, likely due to type 1 segmental mosaicism, as no germline or somatic mutation in the CYLD gene was found. This type of mosaicism involves a de novo postzygotic somatic mutation without a germline mutation, leading to localized lesions. The case adds to the limited reports of Blaschko-linear trichoepitheliomas, highlighting the genetic complexity and rarity of such presentations.