| Feature | Immune Thrombocytopenia (ITP) | Thrombotic Thrombocytopenic Purpura (TTP) |
|---|---|---|
| Pathophysiology | Autoantibody-mediated destruction of platelets | Deficiency of ADAMTS13 enzyme leading to excessive platelet aggregation |
| Platelet Count | Usually moderately low (20,000-70,000/μL) | Severely low (<20,000/μL) |
| Coagulation Tests | Normal PT, PTT | Normal PT, PTT |
| Organ Involvement | Limited systemic involvement | Widespread (brain, kidneys, heart) |
| Neurological Symptoms | Rare | Common (confusion, headache, seizures, stroke) |
| Renal Involvement | Rare | Common (acute kidney injury) |
| Microangiopathic Hemolytic Anemia | Absent | Present (schistocytes on blood smear) |
| Fever | Uncommon | Common |
| Primary Treatment | Corticosteroids, IVIG, anti-D | Plasma exchange, rituximab |
| Mortality without Treatment | Low | High (>90%) |
| Age Distribution | Bimodal (young adults and elderly) | Adults (more common in women) |
| Associated Conditions | Autoimmune disorders | Pregnancy, medications, infections, cancers |
Antiplatelet antibodies (mostly IgG directed against, e.g., GpIIb/IIIa, GpIb/IX) bind to surface proteins on platelets → sequestration by spleen and liver → ↓ platelet count → bone marrow megakaryocytes and platelet production increase in response (in most cases).