Cutaneous arteritis with intimal fibrin ring and immature myeloid cell infiltrate: lymphocytic thrombophilic arteritis or histiocytoid polyarteritis nodosa?

The ongoing debate on whether lymphocytic thrombophilic arteritis (LTA) is a separate disease or a type of polyarteritis nodosa (PAN) has yet to be settled. In this study, we analyzed the nature of infiltrating cells in LTA to resolve this controversy. Skin biopsies from five female patients (mean age 29.4 years, age range 16-45 years) diagnosed with LTA were immunostained for CD3, CD20, CD68, lysozyme, myeloid cell nuclear differentiation antigen, myeloperoxidase, and PU.1. Immunohistochemistry revealed that the majority of mononuclear cells in all five cases were not lymphocytes but myelomonocytic cells. Given that the infiltrating cells are of the myelomonocyte lineage including immature myeloid cells, PAN was deemed the more appropriate diagnosis for the five cases rather than LTA. Whether PAN with immature myeloid cells (histiocytoid PAN) is the same disease as conventional PAN with mature neutrophils requires further investigation.