Overview
Definition
An autoimmune bleeding disorder characterized by isolated low platelet counts (thrombocytopenia) in the absence of a known cause.
Epidemiology
Acute form is common in children (often following a viral illness). Chronic form is more common in adult women.
Etiology & Risk Factors
- Autoantibodies (IgG) bind to platelet surface antigens (e.g., GPIIb/IIIa).
- The antibody-coated platelets are then prematurely destroyed by macrophages in the spleen.
- There is also impaired platelet production in the bone marrow.
Clinical Symptoms
- Often asymptomatic if platelets > 30,000
- Mucocutaneous bleeding: Petechiae (pinpoint red spots), purpura, easily bruising
- Epistaxis (nosebleeds), bleeding gums, heavy menstrual bleeding
- NO splenomegaly (if the spleen is huge, think of another diagnosis like leukemia or cirrhosis)
Clinical Approach
Diagnosis
- Diagnosis of exclusion.
- CBC: Isolated thrombocytopenia. WBCs and RBCs are completely NORMAL.
- Peripheral smear: Normal morphology, possibly some large platelets (megathrombocytes). NO schistocytes (which would suggest TTP).
Management
- Children: Usually self-limiting, requires only observation. Steroids or IVIG if severe bleeding.
- Adults (Platelets < 30,000 or actively bleeding):
- First-line: Corticosteroids (Prednisone, Dexamethasone)
- If active, severe bleeding or needing rapid increase: IVIG (Intravenous Immunoglobulin)
- Refractory disease: Splenectomy, Rituximab, or Thrombopoietin Receptor Agonists (Romiplostim, Eltrombopag)
Complications
- Intracranial hemorrhage (rare but life-threatening complication if platelets drop dangerously low)