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Case Reports

Abstract

Intralymphatic histiocytosis is a rare benign condition involving intradermal lymphatic vessels, which is characterized by a reactive proliferation of lymphatic vessels and intraluminal granuloma-like aggregates of histiocytes. The patient was a 74-year-old man presenting with an ill-defined violaceous xerotic plaque on his left calf. He has a history of left total knee arthroplasty. Upon examination of the punch biopsy, there were markedly ectatic lymphatic vessels lined by bland endothelial cells. Within these vessels, there were prominent collections of cells with bland nuclei and abundant eosinophilic cytoplasm.  Immunohistochemistry confirmed that the vascular channels were lymphatic in nature (D2-40+) and that the intravascular cells were histiocytes (PU.1 and CD68+).  In the surrounding dermis, there was a perivascular mixed intradermal infiltrate composed of lymphocytes, histiocytes, plasma cells, and neutrophils. PAS and Treponema pallidum stains were negative for fungi and spirochetes, respectively. A CD123 stain was negative for clusters of plasmacytoid dendritic cells.Intralymphatic histiocytosis is a rare condition characterized by hallmark features of intradermal lymphatic vessel proliferation and intravascular granuloma-like histiocytic aggregates. While the exact underlying etiology remains elusive, studies have identified correlations with a broad spectrum of inflammatory conditions including rheumatoid arthritis, Crohn disease, cancer surgery, orthopedic metal implants, chronic tonsillitis, and monoclonal gammopathy. Patients have been successfully treated with a variety of anti-inflammatory medication such as tocilizumab, infliximab, and pentoxifylline, may additionally support a reactive cause.