Extracutaneous intravascular histiocytosis of the aortic valve: Report of two cases.

Intravascular histiocytosis (IVH) is a rare condition of uncertain pathogenesis often associated with rheumatoid arthritis (RA) exclusively observed in the skin. In a retrospective study of 207 consecutive cases of aortic valve disease, we observed two cases of IVH characterized by the presence of thin-walled, dilated blood vessels containing collections of CD68+ and CD163+ mononuclear histiocytes. Immunostains for CD31, CD34, and D2-40 confirmed the intravascular location of these histiocytes. One of the two cases was associated with RA. This case was observed among 41 cases of RA with calcific aortic valve stenosis. The other case was detected among 152 cases of calcific aortic valve stenosis in isolation. A total of 14 valves showed no calcification. IVH can manifest in the aortic valve and be associated with systemic disease. In contrast to other cases, the vessels observed in this study exhibited negative expression of the lymphatic marker D2-40. Our findings expand on the previously described location features of IVH.