Thrombocytopenia Causes and Management

Primary Mechanisms of Thrombocytopenia

Low platelet counts result from four primary mechanisms: decreased production, increased destruction, splenic sequestration, or dilution, with immune thrombocytopenia (ITP) and drug-induced thrombocytopenia being the most common causes in otherwise healthy patients with isolated thrombocytopenia 1, 2, 3
Primary immune thrombocytopenia (ITP) - autoimmune destruction of platelets with platelet counts typically <100 × 10⁹/L in the absence of other identifiable causes 1, 2, 3
Secondary ITP associated with autoimmune diseases, viral infections, and certain drugs 1, 2, 3, 5
Drug-induced thrombocytopenia from medications including heparin, antibiotics, diuretics, and chemotherapy agents 1, 6
Heparin-induced thrombocytopenia (HIT) - a prothrombotic condition with thrombocytopenia typically occurring 5-10 days after heparin initiation, with platelet counts usually between 30-70 × 10⁹/L and rarely below 20 × 10⁹/L 6
Portal hypertension and cirrhosis causing splenomegaly with platelet sequestration 7
Pregnancy-related thrombocytopenia 1

Complete blood count with differential to identify isolated thrombocytopenia versus other cytopenias 8
Peripheral blood smear examination to assess platelet size, identify schistocytes, evaluate red and white cell morphology, and confirm true thrombocytopenia 8
Key smear findings in ITP: Normal to large platelets, normal red cell morphology, normal white cell morphology 8

Bleeding risk correlates with platelet count: >50 × 10⁹/L generally asymptomatic, 20-50 × 10⁹/L mild skin manifestations, <10 × 10⁹/L high risk of serious bleeding 6
First-line therapy for pediatric ITP requiring treatment: Single dose IVIg or short course of corticosteroids 1, 2, 5, 3
Children with no bleeding or only mild bleeding should be observed regardless of platelet count 1, 2, 5, 3, 4
Second-line options for refractory ITP: Thrombopoietin receptor agonists, rituximab, fostamatinib, or splenectomy 10
Discontinue the offending agent immediately in drug-induced thrombocytopenia
Stop all heparin immediately and initiate alternative anticoagulation with a non-heparin agent in heparin-induced thrombocytopenia 6

Transfuse platelets for active hemorrhage regardless of platelet count, platelet count <10 × 10⁹/L even without bleeding, or before high-risk procedures when platelets <50 × 10⁹/L 7
Important limitation: In liver disease, prophylactic platelet transfusions to prevent procedural bleeding lack evidence of benefit and carry transfusion-related risks 7