Purpuras

Purpura is the consequence of a dermal extravasation of red cells. The purpura presentation is relevant for the diagnostic orientation: petechial purpura, ecchymoses, infiltrated or necrotic purpura. Thrombocytopenia is a frequent cause of purpura and induces petechial purpura or ecchymoses. Thrombocytopenia with normal medullar analysis may be due to infection (viral or bacterial), drugs, auto-immune disease or is idiopathic (idiopathic thrombocytopenic purpura). Thrombocytopenia may be one of the elements of severe disseminated intravascular coagulation or purpura fulminans. Decreased production of platelets may be due to diverse bone marrow diseases, congenital or acquired. Abnormal platelet functions are less frequently observed. Skin aging, vitamin C deficiency, or prolonged corticoid therapy may induce ecchymotic purpura due to frail vascular walls. Necrotic purpura, generally associated with inflammatory livedo and skin necrosis, may be due to microvascular thrombosis (platelet plugs (heparin, myeloproliferative diseases with thrombocytosis), occlusion due to infective agents growing in vessels, alterations in coagulation control (protein C or S deficiency, antiphospholipids)) or embolization (fat embolization, cholesterol emboli, myxoma). Palpable (infiltrated) and inflammatory pupuras require skin biopsy seeking leukocytoclastic vasculitis. Chronic pigmented purpuras represent a group of characteristic anatomo-clinical entities, of chronic but benign evolution. Pathogenesis is unknown. Some dermatosis may be purpuric (urticaria, drug reactions, erysipelas, pityriasis lichenoides). Some purpuras are characterized by their topography (socks and gloves syndrome) or their context (Gardner-Diamond syndrome). Pediatric entities are neonatal purpura fulminans (protein S or C deficiency), Henoch-Schonlein purpura, acute hemorrhagic oedema of childhood.