Hematology · Platelet Disorders
The facts most likely to be tested
ITP is an autoimmune disorder characterized by isolated thrombocytopenia caused by anti-platelet IgG autoantibodies directed against the GPIIb/IIIa or GPIb/IX complex.
The diagnosis of ITP is a diagnosis of exclusion requiring a peripheral blood smear to rule out pseudothrombocytopenia and other causes of low platelets.
Patients with ITP typically present with mucocutaneous bleeding, including petechiae, purpura, and epistaxis, in the absence of splenomegaly or systemic symptoms.
First-line treatment for adults with a platelet count < 30,000/µL or active bleeding is corticosteroids or intravenous immunoglobulin (IVIG).
Splenectomy remains a definitive second-line treatment option for patients who are refractory to initial medical therapy or have chronic ITP.
Thrombopoietin receptor agonists (TPO-RAs) like eltrombopag or romiplostim are indicated for patients with chronic ITP who have failed first-line therapy or are not candidates for surgery.
Children with ITP often present with a history of a recent viral infection and typically experience spontaneous resolution within six months.
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A 28-year-old woman presents to the clinic complaining of easy bruising and bleeding gums for the past week. She reports no recent medication changes, fever, or weight loss. Physical examination reveals scattered petechiae on the lower extremities and ecchymoses on the arms, but no splenomegaly or lymphadenopathy. Laboratory studies show a platelet count of 18,000/µL, while hemoglobin and white blood cell counts are within normal limits. A peripheral blood smear confirms isolated thrombocytopenia with no evidence of schistocytes or blasts.
What is the most appropriate initial management for this patient?
Corticosteroids
The patient presents with classic signs of ITP (isolated thrombocytopenia, no splenomegaly, normal smear). Since the platelet count is < 30,000/µL, first-line treatment with corticosteroids is indicated to reduce autoantibody production and splenic sequestration.
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Etiology / Epidemiology
Autoimmune destruction of platelets; common in children post-viral and adult women.
Clinical Manifestations
Isolated thrombocytopenia presenting with mucocutaneous bleeding and petechiae.
Diagnosis
Diagnosis of exclusion; platelet count <100,000/µL with normal peripheral smear.
Treatment
First-line: corticosteroids; avoid platelet transfusions unless life-threatening.
Prognosis
Most children achieve spontaneous remission within 6 months; adults often chronic.
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Epidemiology & Etiology
ITP is an acquired autoimmune disorder characterized by isolated thrombocytopenia. In children, it often follows a viral exanthem. In adults, it is frequently idiopathic or associated with SLE, CLL, or HIV.
Pertinent Anatomy
The spleen is the primary site of platelet destruction and antibody production. Splenomegaly is notably absent in classic ITP; its presence suggests an alternative diagnosis.
Pathophysiology
Autoantibodies (usually IgG) bind to platelet surface glycoproteins (GPIIb/IIIa). These antibody-coated platelets are sequestered and destroyed by macrophages in the spleen. The bone marrow compensates by increasing megakaryocyte production, but destruction outpaces synthesis.
Clinical Manifestations
Patients present with petechiae, purpura, and epistaxis. Intracranial hemorrhage is the most feared complication. Physical exam is typically unremarkable except for signs of bleeding; splenomegaly should prompt investigation for other etiologies.
Diagnosis
ITP is a diagnosis of exclusion. The peripheral blood smear is mandatory to rule out pseudothrombocytopenia and schistocytes. A platelet count <100,000/µL is the diagnostic threshold in the absence of other causes.
Treatment
First-line therapy is corticosteroids (prednisone). If platelets are <30,000/µL or active bleeding occurs, add IVIG. Platelet transfusions are generally contraindicated as they are rapidly destroyed. Refractory cases may require rituximab or splenectomy.
Prognosis
Pediatric cases are usually self-limiting with 80% remission within 6 months. Adult cases are more likely to become chronic and require long-term monitoring for bleeding diathesis.
Differential Diagnosis
TTP: presence of schistocytes and pentad of symptoms
HUS: associated with bloody diarrhea and renal failure
DIC: abnormal PT/PTT and fibrinogen levels
Leukemia: presence of blasts on peripheral smear
Drug-induced thrombocytopenia: history of heparin or sulfa exposure