Rare: more common in elderly
Intracerebral bleeding
Severe GI bleeding
Intracerebral bleeding
Severe GI bleeding
Immune thrombocytopenic purpura
Marrow infiltration 
Thrombotic thrombocytopenic purpura
Viral infections 
Disseminated intravascular coagulation
Marrow suppression 
Heparin-Induced Thrombocytopenia 
Congenital thrombocytopenia