What is Immune Thrombocytopenic Purpura (ITP)?
ITP is an autoimmune disorder characterized by immunologic destruction of otherwise normal platelets, resulting in isolated thrombocytopenia (platelet count <100 × 10⁹/L) in the absence of other identifiable causes. 1, 2
Pathophysiology
The condition involves both increased platelet destruction and impaired platelet production due to autoimmune mechanisms, contrary to historical beliefs that only destruction was involved. 1
IgG autoantibodies bind to platelets and megakaryocytes, leading to accelerated destruction by the reticuloendothelial system while simultaneously impairing megakaryocytic function. 3
The immune response involves both innate and adaptive immune systems, comprising humoral and cell-mediated components. 4
Classification
Primary ITP occurs in isolation without an identifiable cause. 1
Secondary ITP is associated with other disorders, including viral infections (HIV, HCV), H. pylori, and other autoimmune conditions. 1, 2
Duration-based classification: newly diagnosed, persistent (3-12 months), and chronic (≥12 months). 1, 5
Epidemiology
Incidence is 2-5 cases per 100,000 population. 1
Children have dramatically higher spontaneous remission rates: 74% in children <1 year, 67% in ages 1-6 years, and 62% in ages 10-20 years. 1, 2, 5
Adults have significantly worse outcomes: only 20-45% achieve complete remission by 6 months, with a 1.3-2.2-fold higher mortality than the general population due to cardiovascular disease, infection, and bleeding. 1, 5
Clinical Presentation
Most patients have minimal symptoms such as bruising and petechiae. 1
More serious manifestations include mucosal bleeding, gastrointestinal hemorrhage, and hematuria. 1
Intracranial hemorrhage is rare but serious, occurring in 1.4% of adults and 0.1-0.4% of children. 1
Severe bleeding is reported in 9.5% of adults and 20.2% of children. 1
Quality of life impairment and fatigue are significant concerns, especially in the first year after diagnosis. 2
Diagnosis
ITP is a diagnosis of exclusion requiring isolated thrombocytopenia, normal peripheral blood smear except for reduced platelets, and absence of other obvious causes of thrombocytopenia. 1, 2
Bone marrow examination is generally unnecessary in children and adolescents with typical ITP features, children who fail IVIg therapy, and patients prior to corticosteroid treatment or splenectomy. 1
Secondary causes (HIV, HCV, H. pylori) should be identified and treated when present. 2
Treatment Principles
Treatment decisions are based on bleeding risk rather than platelet count alone. 1, 2, 5
For children with no bleeding or mild bleeding, observation alone is recommended regardless of platelet count. 1
The goal is to achieve and maintain platelet counts ≥50 × 10⁹/L as necessary to reduce bleeding risk, not to normalize platelet counts. 6
First-line treatments include IVIg (0.8-1 g/kg), corticosteroids (prednisone 1-2 mg/kg/day), and IV anti-D immunoglobulin (50-75 μg/kg) for Rh(D)-positive patients. 1, 2, 5
Platelet transfusions are generally ineffective except in emergency situations due to rapid destruction. 2