Plasmacytoid dendritic cells in angiolymphoid hyperplasia with eosinophilia

Background: Angiolymphoid hyperplasia with eosinophilia (ALHE) is characterized by irregularly-shaped blood vessels with an inflammatory infiltrate. While absent from normal skin, plasmacytoid dendritic cells (pDCs) infiltrate the skin upon injury and during several infectious, inflammatory, and neoplastic entities. In addition to providing anti-viral resistance, pDCs link the innate and adaptive immune responses. In Kimura’s disease (KD), pDCs have been reported to occur. Here, we investigate pDCs in ALHE. Methods: Five ALHE and comparable 4 KD cases were immunohistochemically tested for pDC occurrence and type I IFN production using anti-BDCA-2 and anti- myxovirus protein A (MxA) antibodies, respectively. A semiquantitative scoring system was used. Results: Plasmacytoid dendritic cells were present in all ALHE and KD cases with no statistically significant differences, while MxA expression was weak and patchy in most ALHE and KD cases. Conclusions: pDCs are recruited into the lesions of ALHE. Despite the diminished ability to produce type I IFNs, the consistent presence of pDCs in all ALHE cases is in favor of some role of these cells in ALHE pathogenesis.