Purpura

Purpura (ˈpɜːrpjʊərə) is a condition of red or purple discolored spots on the skin that do not blanch on applying pressure. The spots are caused by bleeding underneath the skin secondary to platelet disorders, vascular disorders, coagulation disorders, or other causes. They measure 3–10 mm, whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm. Purpura is common with typhus and can be present with meningitis caused by meningococci or septicaemia. In particular, meningococcus (Neisseria meningitidis), a Gram-negative diplococcus organism, releases endotoxin when it lyses. Endotoxin activates the Hageman factor (clotting factor XII), which causes disseminated intravascular coagulation (DIC). The DIC is what appears as a rash on the affected individual. Purpura are a common and nonspecific medical sign; however, the underlying mechanism commonly involves one of: Platelet disorders (thrombocytopenic purpura) Primary thrombocytopenic purpura Secondary thrombocytopenic purpura Post-transfusion purpura Vascular disorders (nonthrombocytopenic purpura) Microvascular injury, as seen in senile (old age) purpura, when blood vessels are more easily damaged Hypertensive states Deficient vascular support Vasculitis, as in the case of Henoch–Schönlein purpura Coagulation disorders Disseminated intravascular coagulation (DIC) Scurvy (vitamin C deficiency) – defect in collagen synthesis due to lack of hydroxylation of procollagen results in weakened capillary walls and cells Meningococcemia Clumping fibrillary protein deposits caused by Amyloidosis Cocaine use with concomitant use of the one-time chemotherapy drug and now veterinary deworming agent levamisole can cause purpura of the ears, face, trunk, or extremities, sometimes needing reconstructive surgery. Levamisole is purportedly a common cutting agent. Decomposition of blood vessels including purpura is a symptom of acute radiation poisoning in excess of 2 Grays of radiation exposure. This is an uncommon cause in general, but is commonly seen in victims of nuclear disaster.