Causes of thrombocytopenia

Decreased platelet production

• Aplastic anemia
• Bone marrow damage from chemo/radiation therapy
  
• Congenital or acquired bone marrow aplasia or hypoplasia
• Acquired pure megakaryotic aplasia
• Leukemia
• Myelofibrosis
• Myelodysplastic syndrome
• Damage to megakaryocytes (HIV)
• Vitamin B12 and folate deficiency
  
• Thrombocytopenia with absent radius syndrome

Increased platelet destruction

• Immune-mediated -- PRIMARY: ITP SECONDARY: infection (HIV, herpes, HCV), SLE, antiphospholipid syndrome, alloimmune destruction (post-transfusion), drugs (heparin-induced thrombocytopenia*, abciximab, quinidine, sufonamides, vancomycin)

• Non-immune-mediated--- DIC, TTP, HUS, HELLP syndrome, preeclampsia, cardiopulmonary bypass

Sequestration

• Congestive splenomegaly 2/2 cirrhosis and portal hypertension

Pseudothrombocytopenia (EDTA-induced platelet clumping)
Dilutional thrombocytopenia (after massive PRBC transfusion)