Intralymphatic histiocytosis following placement of a metal implant

Intralymphatic histiocytosis (IH) is a rare condition first reported in 1994 by O'Grady et al. Less than 40 cases have been reported, with the majority occurring in patients with rheumatoid arthritis. We present a case of a 72-year-old man who developed an asymptomatic rash on his left upper arm 3 years after placement of a metal implant to stabilize a fractured humerus. Examinations revealed a poorly demarcated erythematous to brown indurated plaque with a pebbly surface overlying the inferior portion of the surgical scar. Biopsy revealed a mixed dermal infiltrate with a complex glomeruloid intravascular accumulation of histiocytes and neutrophils. Histiocytes were identified with immunostaining for CD68. Immunostains for CD31 and D2-40 confirmed the intravascular location of the histiocytes. This reactive process is closely related to reactive angioendotheliomatosis, but is best classified as IH. This is the only case of IH reported in association with a metal implant of the upper arm and the fourth case reported in association with a metal implant. Although the pathogenesis of IH is unknown, a role for lymphatic stasis secondary to chronic inflammation or surgery has been suggested. This is a benign process with a chronic course, and there are no known efficacious treatments.