Marrow infiltration (tumor or infection)
Viral infections (rubella, HIV)
Marrow suppression (commonly chemotherapy or radiation)
Congenital<unk> 
Fanconi anemia
Alport syndrome
Bernand Soulier
Vitamin B12 and/or folate deficiency
Fanconi anemia
Alport syndrome
Bernand Soulier
Idiopathic<unk>  purpura
Thrombotic<unk>  Purpura (TTP)
Hemolytic Uremic Syndrome (HUS)
Disseminated Intravascular Coagulation (DIC)
Viral infections (HIV, mumps, varicella, EBV)
Drugs<unk> , protamine)
Postransfusion or Posttransplantation
Autoimmune destruction (SLE or Sarcoidosis)
Mechanical destruction
Artificial valves
ECMO
HELLP syndrome
Excessive hemorrhage
Hemodialysis, extracorporeal circulation
Splenic Sequestration
Occurs in Sickle cell disease and Cirrhosis
Artificial valves
ECMO
Occurs in Sickle cell disease and Cirrhosis
sulfa antibiotics, ETOH, ASA, thiazide diuretics/furosemide
Disseminated Intravascular Coagulation (DIC)
Thrombotic<unk>  Purpura (TTP)
Hemolytic Uremic Syndrome (HUS)
HELLP syndrome<unk> (HIT)
Hereditary spherocytosis
Paroxysmal nocturnal hemoglobinuria (PNH)
Malignant hypertension
Scleroderma
Antiphospholipid Syndrome (APS)
Other medical causes: malignancy, renal allograft rejection, vasculitides like polyarteritis nodosa and Wegener's granulomatosis
Drugs: chemotherapy; Clopidogrel (Plavix) associated with TTP
Nonvascular causes: prosthetic valve (more common with mechanical, more common at aortic valve), LVAD, TIPS, coil embolization, patched AV shunt, AVM
Heparin-Induced Thrombocytopenia 
Marrow infiltration 
Disseminated intravascular coagulation
Viral infections 
Liver disease induced coagulopathy
Marrow suppression 
Vitamin K deficiency
Congenital thrombocytopenia