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
Definition and Pathophysiology
- ITP has been variably defined as "immune thrombocytopenic purpura," "idiopathic thrombocytopenic purpura," and most recently "immune thrombocytopenia" 1
- The condition involves both increased platelet destruction and impaired platelet production due to autoimmune mechanisms 1
- Historically, ITP was believed to be caused solely by increased platelet destruction, but newer evidence shows platelet production is also decreased in many patients 1
Classification
Primary ITP occurs in isolation without an identifiable cause 1, 2
Secondary ITP is associated with other disorders, including: 1
- Autoimmune diseases (particularly antiphospholipid antibody syndrome)
- Viral infections (including hepatitis C and HIV)
- Certain medications
ITP is classified by duration: 2
- Newly diagnosed
- Persistent (3-12 months)
- Chronic (≥12 months)
Epidemiology
- ITP has an incidence of 2-5 cases per 100,000 population 1
- The likelihood of spontaneous remission is age-related: 1, 3
- 74% in children <1 year of age
- 67% in children between 1-6 years
- 62% in children 10-20 years (at 1 year)
- In adults, only 20-45% achieve complete remission by 6 months 1, 2
- Adults with ITP have a 1.3-2.2-fold higher mortality than the general population due to cardiovascular disease, infection, and bleeding 1
Clinical Presentation
- Many patients have minimal symptoms (bruising and petechiae) 1, 2
- More serious mucosal bleeding may occur, including: 1, 2
- Menorrhagia
- Epistaxis
- Gastrointestinal hemorrhage
- Hematuria
- Intracranial hemorrhage is rare but serious, reported 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
Diagnosis
ITP is a diagnosis of exclusion requiring: 1, 3
- 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
Impact on Quality of Life
- ITP significantly impacts health-related quality of life, particularly in the first year after diagnosis 1, 3
- Fatigue is common, reported in 22-45% of patients 1
- Restrictions on activities and anxiety due to bleeding risk contribute to reduced quality of life 1, 2
Treatment Approach
Treatment decisions should be based on bleeding risk rather than platelet count alone 3
For children with no bleeding or mild bleeding (skin manifestations only), observation alone is recommended regardless of platelet count 1
First-line treatments include: 1, 3
- IVIg (0.8-1 g/kg)
- Corticosteroids (short-term use)
- IV anti-D immunoglobulin (50-75 μg/kg) for Rh(D)-positive patients
Second-line therapies for refractory cases include: 4
- Splenectomy
- Rituximab (anti-CD20 monoclonal antibody)
For chronic refractory ITP, thrombopoietin receptor agonists like romiplostim may be used 5
Prognosis
- Children have a generally favorable prognosis with high spontaneous remission rates 1, 3
- Adult ITP is more likely to become chronic, with lower remission rates 1, 2
- Regular monitoring of platelet counts and bleeding symptoms is essential 3