thrombocytopenic purpura: purpura associated with a reduction in circulating blood platelets which can result from a variety of factors
autoimmune disease: any of a large group of diseases characterized by abnormal functioning of the immune system that causes your immune system to produce antibodies against your own tissues
wood rat: any of various small short-tailed rodents of the northern hemisphere having soft fur grey above and white below with furred tails and large ears; some are hosts for Ixodes pacificus and Ixodes scapularis (Lyme disease ticks)