Cutaneous reactive angiomatoses: patterns and classification of reactive vascular proliferation

New and relatively old types of vascular (capillary) proliferations in the skin have been described or better categorized in the last few years. They include reactive angioendotheliomatosis, acroangiodermatitis (pseudo-Kaposi sarcoma), diffuse dermal angiomatosis, intravascular histocytosis, glomeruloid angioendotheliomatosis, and angiopericytomatosis (angiomatosis with cryoproteins). Clinically, all of them present with multiple, erythematous-violaceous and purpuric patches and plaques, sometimes evolving toward necrosis and ulceration with a wide distribution but a propensity to involve limbs. Histologically, they are characterized by different patterns of intravascular or extravascular lobular or diffuse hyperplasia of endothelial cells, pericytes, and sometimes histiocytes. Although these angioproliferations can histologically mimic vascular tumors, they are reactive in that they seem to originate from the occlusion of vascular lumina by different localized or systemic disorders and the vascular proliferation stops after the inducing hypoxic stimulus has been withdrawn. In this article, the authors review all these forms of reactive angioproliferations in the skin, suggest a novel title, cutaneous reactive angiomatoses, and propose a unifying pathogenetic mechanism.