Abstract

Reactive angioendotheliomatosis (RAE) is a benign cutaneous vascular proliferation that has been reported in association with a variety of conditions, including cryoglobulinemia, hypercoagulable conditions, infections, end-stage renal disease, and malignancies, among others. It has also been reported at the site of arteriovenous fistulas. However, the exact etiology of RAE and extent of associated conditions has not been fully characterized. We present a case of RAE at the site of insulin injections in a patient with diabetes mellitus. A 61-year-old man with past medical history of diabetes mellitus controlled by insulin presented with a red, livedoid, tender plaque with surrounding dusky discoloration on his abdomen at the site of his injections. He reportedly developed similar lesions in the past, which had previously healed spontaneously. A punch biopsy of the lesion revealed a superficial to deep dermal interstitial proliferation of well-formed, small, angulated, and thin-walled vessels. The endothelial cells demonstrate enlarged, plump nuclei. The overlying epidermis is ulcerated and has a patchy dermal lymphohistiocytic infiltrate. On immunohistochemistry, the endothelial cells are positive for CD31, CD34, and ERG, while smooth muscle actin highlights a well-formed myopericytic layer. The endothelial cells are negative for HHV-8. CD68 and CD163 highlight the numerous intervening background histiocytes and colloidal iron stains demonstrate increased dermal mucin. The clinical and histologic findings were consistent with reactive angioendotheliomatosis. This case represents the first possible association between insulin injections and RAE and highlights the importance of considering this entity in the differential of vascular proliferations in patients with underlying systemic disease.