What is Immune Thrombocytopenic Purpura (ITP)?

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

Pathophysiology

• The condition involves both increased platelet destruction and impaired platelet production due to autoimmune mechanisms, contrary to older beliefs that only destruction was involved 1
• IgG autoantibodies bind to platelets and megakaryocytes, leading to T cell-mediated platelet destruction and impaired megakaryocytic function 2
• The reticuloendothelial system destroys these opsonized platelets, resulting in low peripheral blood platelet counts 3

Classification Systems

By Etiology:

• Primary ITP occurs in isolation without an identifiable cause 1
• Secondary ITP is associated with other disorders, including viral infections (HIV, HCV), H. pylori, or other autoimmune conditions 1, 4

By Duration:

• Newly diagnosed: Initial presentation 1
• Persistent: 3-12 months duration 1, 5
• Chronic: ≥12 months duration 1, 5

Epidemiology

• Incidence is 2-5 cases per 100,000 population 1
• Higher incidence in females than males (incident rate ratio 3.19) 6
• Significantly higher in Black compared with non-Black individuals (incident rate ratio 7.09) 6
• Adults have a 1.3-2.2-fold higher mortality than the general population due to cardiovascular disease, infection, and bleeding 1, 5

Clinical Presentation

Common Symptoms:

• Many patients have minimal symptoms such as bruising and petechiae 1
• Neurologic symptoms (headache, confusion, seizures) occur in 39-80% of cases 6
• Abdominal pain presents in 35-39% of patients 6

Serious Bleeding Manifestations:

• Mucosal bleeding including gastrointestinal hemorrhage and hematuria 1
• Intracranial hemorrhage is rare but serious: 1.4% in adults and 0.1-0.4% in children 1
• Severe bleeding is reported in 9.5% of adults and 20.2% of children 1

Diagnostic Criteria

ITP is a diagnosis of exclusion requiring: 1, 4

• Isolated thrombocytopenia (platelet count <100 × 10⁹/L)
• Normal peripheral blood smear except for reduced platelets
• Absence of other obvious causes of thrombocytopenia

Bone marrow examination is generally unnecessary in: 1

• Children and adolescents with typical ITP features
• Children who fail IVIg therapy
• Patients prior to corticosteroid treatment or splenectomy

Prognosis

Pediatric Patients:

• High spontaneous remission rates: 74% in children <1 year, 67% in ages 1-6 years, and 62% in ages 10-20 years 1, 4, 5
• Generally favorable prognosis 1

Adult Patients:

• More likely to become chronic with lower remission rates 1
• Only 20-45% achieve complete remission by 6 months 4, 5
• Significantly impacts quality of life, particularly in the first year after diagnosis 5