Monoclonal Annular Lichenoid Dermatitis of Youth as a New Entity: A Case Report and Review of the Literature.

Annular lichenoid dermatitis of youth (ALDY) is a rare lichenoid dermatosis characterized by distinctive clinical and histopathological features. Its etiopathogenesis remains poorly understood, and previously reported cases have consistently demonstrated polyclonal T-cell receptor (TCR) gene rearrangements. We report a patient with clinical, histopathological, and immunohistochemical findings consistent with ALDY in whom molecular analysis revealed monoclonal T-cell receptor rearrangement within the skin lesions. To our knowledge, this represents the first reported case of ALDY demonstrating T-cell monoclonality. This novel finding expands the current understanding of the molecular spectrum of ALDY and raises the possibility that cases with monoclonal T-cell rearrangement may represent a distinct clinicopathological variant. Based on our findings, we tentatively propose the term monoclonal annular lichenoid dermatitis of youth (MALDY) to describe this potential entity. Further studies are warranted to clarify its clinical significance and relationship to other cutaneous T-cell disorders.