Certain medications that affect how platelets in the blood stream function are known to cause both types of purpura, according to Healthline. Additionally, weakened or inflamed blood vessels could cause nonthrombocytopenic purpura, while recent blood transfusions and blood infections can cause thrombocytopenic purpura.
Nonthrombocytopenic purpura is characterized by a normal platelet count, and patients with thrombocytopenic purpura have lower-than-average platelet counts, states Healthline. Additional causes of nonthrombocytopenic purpura include certain congenital disorders, such as rubella and cytomegalovirus, as well as a severe lack of vitamin C, called scurvy. Additional causes of thrombocytopenic puroura include idiopathic thrombocytopenic purpura, which is an immune disorder that, as of 2015, has no known cause.