Type 1 IFN-induced protein MxA and plasmacytoid dendritic cells in lesions of morphea

Morphea is an autoimmune sclerotic skin disease of unknown pathogenesis. As type 1 interferons (IFN) have been implicated in the pathogenesis of systemic sclerosis, we proposed that type 1 IFN promote localized inflammation and fibrosis in morphea. To investigate the expression of the type 1 IFN-inducible protein myxovirus A (MxA) and the presence of plasmacytoid dendritic cells (pDC) in lesions of morphea, lesional skin of 10 patients with morphea was examined by immunohistochemistry for the presence of the type 1 IFN-inducible protein, myxovirus A (MxA), and the pDC markers, CD123 and BDCA-2, and was compared with lesional skin of cutaneous lupus erythematosus, lichen planus and keloid. Lesional and non-lesional morphea skin was compared. MxA was expressed in the epidermis as well as the reticular dermis and subcutis in morphea. pDCs were abundant around vessels and between fibrous bundles. Non-lesional biopsies demonstrated little or no expression of MxA and pDC markers. Keloid showed minimal expression of MxA and pDC markers. We demonstrate the expression of type 1 IFN-related protein MxA and plasmacytoid DCs in lesional but not in non-lesional biopsies of morphea. These findings suggest a potential role for type 1 interferons in the pathogenesis of morphea.