Immune Thrombocytopenic Purpura (ITP)

Related Subjects: |Microangiopathic Haemolytic anaemia |Haemolytic anaemia |Immune(Idiopathic) Thrombocytopenic Purpura (ITP) |Thrombotic Thrombocytopenic purpura (TTP) |Haemolytic Uraemic syndrome (HUS) |Thrombocytopenia |Disseminated Intravascular Coagulation (DIC)

A disorder of isolated thrombocytopenia caused by immune-mediated platelet destruction.

📖 About

• Defined as platelet count <150 × 10⁹/L 🧪.
• Antibodies target and destroy platelets via the reticuloendothelial system ⚡.
• Classified into acute (children, post-viral) and chronic (adults, often secondary to SLE, HIV, CLL).

📊 Patterns

• Acute ITP (AITP): Common in children 👧, often post-viral, self-limiting.
• Chronic ITP (CITP): Seen in adults, may be idiopathic or secondary to autoimmune disease (SLE), HIV, or haematological malignancy.

⚡ Clinical Features

• Petechiae and purpura 🔴.
• Mucosal bleeding: epistaxis 👃, menorrhagia, gum bleeding.
• GI bleeding, haematuria, or occult blood loss possible.
• No splenomegaly (helps distinguish from other causes).

🔬 Investigations

• FBC: Isolated thrombocytopenia 📉.
• Bone marrow: Normal/increased megakaryocytes (compensatory response).
• DAT (Coombs): Negative (distinguishes from Evans syndrome).
• Platelet antibodies may be detected in chronic ITP.

🩺 General Management

• Supportive: Good IV access, cross-match 2–6 units if bleeding. Platelet transfusions avoided unless life-threatening haemorrhage 🚑.
• 1st line (Rescue): If symptomatic, platelets <30 × 10⁹/L, or prior to invasive procedure:
  • Prednisolone 1–2 mg/kg/day 💊.
  • IV Immunoglobulin (IVIG) 1 g/kg/day ×2 days (critical bleed, steroid-intolerant, or resistant). Works by blocking macrophage Fc receptors 🔒.
• 2nd line: For persistent (>3 months) or chronic ITP (>12 months):
  • Rituximab (375 mg/m² weekly ×4) 💉.
  • Splenectomy (if severe <10–20 × 10⁹/L, high bleed risk, or steroid-dependent). Not ideal for elderly/comorbid patients ⚠️.
  • Romiplostim / Eltrombopag (TPO receptor agonists) if splenectomy fails.

💊 Other Agents

• Mycophenolate mofetil 🌿.
• Azathioprine 💊.
• Ciclosporin A.
• Danazol.
• Dapsone.
• Vinca alkaloids (vincristine/vinblastine).
• Cyclophosphamide.

🛡️ Prevention of Infection Post-Splenectomy

• Vaccination: Pneumococcus, Hib, and meningococcus (A, C, W, Y ± B) 💉.
• Lifelong Penicillin V prophylaxis (500 mg bd) in UK practice 💊.
• Patient education: urgent care for febrile illness 🚨.

📚 References

• SWL ITP Treatment Pathway (UK)
• ASH 2019 Guidelines for ITP

Cases — Immune Thrombocytopenic Purpura (ITP)

• Case 1 — Child with Post-Viral Purpura: A 6-year-old boy develops sudden bruising and petechiae two weeks after a viral upper respiratory infection. He is otherwise well, no hepatosplenomegaly. Platelets 12 ×10⁹/L, Hb and WCC normal. Diagnosis: Acute childhood ITP (often self-limiting).
• Case 2 — Young Woman with Menorrhagia: A 24-year-old woman presents with heavy menstrual bleeding, gum bleeding, and widespread petechiae. Platelets 18 ×10⁹/L, other blood counts normal. No systemic symptoms. Diagnosis: Primary ITP in an adult, requiring treatment due to bleeding.
• Case 3 — Older Patient with Chronic Relapsing ITP: A 68-year-old man with long-standing ITP presents with recurrent nosebleeds and platelet count of 8 ×10⁹/L despite previous courses of steroids. He has hypertension and type 2 diabetes. Diagnosis: Chronic refractory ITP in an older adult.

Teaching Commentary 🩸

ITP is an autoimmune condition where IgG autoantibodies target platelet surface antigens, leading to accelerated splenic destruction. It typically presents with isolated thrombocytopenia (normal Hb/WCC), mucocutaneous bleeding (petechiae, bruising, epistaxis, menorrhagia), and absence of systemic illness. In children, it often follows infection and resolves spontaneously. In adults, it tends to be chronic and relapsing. First-line treatment (if significant bleeding or very low platelets) is corticosteroids or IVIg; second-line includes thrombopoietin receptor agonists (eltrombopag, romiplostim) or rituximab. Splenectomy is rarely used now. Always exclude secondary causes (HIV, hepatitis C, lupus, drugs).