What is Immune Thrombocytopenic Purpura (ITP)?

Immune Thrombocytopenic Purpura (ITP): A Simple Explanation

ITP is an autoimmune disorder where the immune system attacks and destroys platelets, leading to low platelet counts (below 100 × 10^9/L) and increased risk of bleeding. 1

What Causes ITP?

ITP occurs when your immune system mistakenly targets your own platelets:

• Primary ITP: Occurs without any obvious underlying cause
• Secondary ITP: Associated with other conditions such as:
  • Autoimmune diseases (particularly antiphospholipid antibody syndrome)
  • Viral infections (including hepatitis C and HIV)
  • Certain medications 1

The pathophysiology involves:

1. Autoantibodies that opsonize (tag) platelets for destruction
2. Impaired platelet production in the bone marrow
3. T-cell mediated immune effects 1

Clinical Presentation

ITP symptoms vary widely from patient to patient:

• No symptoms or minimal bruising - Many patients have few or no symptoms
• Mild symptoms - Skin manifestations like bruising and petechiae
• Moderate symptoms - Mucosal bleeding (gums, nose)
• Severe symptoms - Gastrointestinal hemorrhage or intracranial hemorrhage (rare but life-threatening) 1

The severity of thrombocytopenia correlates somewhat with bleeding risk, but not completely. Additional factors affecting bleeding risk include:

• Age (older patients at higher risk)
• Lifestyle factors
• Comorbidities
• Use of anticoagulant or antiplatelet medications 1

Diagnosis

ITP is a diagnosis of exclusion. Basic evaluation includes:

• Patient history
• Family history
• Physical examination
• Complete blood count and reticulocyte count
• Peripheral blood film examination
• Quantitative immunoglobulin level measurement 1

Bone marrow examination is generally unnecessary in patients with typical ITP features, particularly in children and adolescents 1.

Classification by Duration

ITP is classified into three categories based on duration:

1. Newly diagnosed: Within 3 months of diagnosis
2. Persistent ITP: 3-12 months duration
3. Chronic ITP: ≥12 months duration 1

Epidemiology

• Annual incidence: 2-5 cases per 100,000 people 1
• Adult ITP: Equal incidence between sexes except in mid-adult years (30-60 years) when it's more common in women
• Childhood ITP: Equal between sexes, often follows viral illness and typically resolves within 6 months 1

Treatment Approach

Treatment decisions are based on:

• Platelet count
• Bleeding symptoms
• Patient age and comorbidities
• Quality of life considerations 1

For Adults:

• Platelet count <30 × 10^9/L with no/minor bleeding: Corticosteroids are suggested rather than observation 1
• Platelet count ≥30 × 10^9/L with no/minor bleeding: Observation is recommended over corticosteroids 1

For Children:

• No bleeding or mild bleeding: Observation alone regardless of platelet count 1
• Requiring treatment: Single dose of IVIg (0.8-1 g/kg) or short course of corticosteroids 1

Second-line Therapies:

For patients not responding to first-line therapy:

• Thrombopoietin receptor agonists (TPO-RAs) like romiplostim
• Rituximab (anti-CD20 monoclonal antibody)
• Splenectomy
• Immunosuppressive agents 2, 3

Prognosis

• Children: 74% remission rate by 1 year in those <1 year of age; 67% in those 1-6 years; 62% in those 10-20 years
• Adults: 20-45% achieve complete remission by 6 months 1
• Adults with ITP have 1.3-2.2 times higher mortality than the general population due to cardiovascular disease, infection, and bleeding 1

Important Considerations

• Intracranial hemorrhage occurs in 1.4% of adults and 0.1-0.4% of children with ITP 1
• Severe bleeding is reported in 9.5% of adults and 20.2% of children 1
• ITP significantly impacts quality of life, particularly in the first year after diagnosis
• Fatigue is common, affecting 22-45% of patients 1

Understanding ITP as an autoimmune condition affecting platelets helps explain both the variable clinical course and the rationale behind treatments that target the immune system or boost platelet production.