Low Platelet Count
Decreased Production
Normal/Increased WBCs
Drugs
Alloimmune
Autoimmune
• Aplastic Anemia
• Toxic Damage (e.g. 
Chemotherapy)
• Displacement (e.g. Leukemia, 
Tumor)
• ITP
• SLE
• CLL
• APLA
• Anti-HLA antibodies • Quinidine
• HIT
• Others
Decreased 
Megakaryopoiesis
Ineffective 
Megakaryopoiesis
• B12 Deficiency
• Folate Deficiency
• Folate Antagonist 
(methotrexate)
• Drugs
Immune
Non-Immune
• HELLP Syndrome
• TTP/HUS
• DIC
• Vasculitis
• Infection
• Foreign Surface (e.g. 
Prosthetic Heart Valve)
Increased Sequestration
• Splenomegaly