Idiopathic thrombocytopenic purpura (ITP) and other platelet disorders

  • Platelet problems can be classified as either deficiency (thrombocytopenia) or dysfunction.
    • There are many causes of thrombocytopenia
      • Decreased production
        • Congenital
          • e.g. Wiskott-Aldrich syndrome (X-linked recessive disease characterised by thrombocytopenia, lymphopenia, immunosuppression, eczema, malignant lymphoma)
          • e.g. Fanconi’s anaemia
        • Acquired
          • Viral infections
          • Aplastic anaemia
          • Marrow infiltration by a malignancy e.g. leukaemia, lymphoma, myeloma, metastatic disease
          • Drugs (most commonly chemotherapy but also quinine and vancomycin)
          • Alcohol and B12/folate deficiency anaemia
          • Myelofibrosis
      • Decreased platelet survival
        • Immune- ITP (see below); SLE, rheumatoid arthritis; sarcoidosis; antiphospholipid syndrome
        • Post-transfusion thrombocytopenic purpura
        • Thrombotic thrombocytopenic purpura
        • Haemolytic uraemic syndrome
        • Disseminated Intravascular coagulation
        • HELLP syndrome and pre-eclampsia
        • Splenomegaly/hypersplenism
    • The most common cause of platelet dysfunction is iatrogenic via the use of anti-platelet drugs e.g. aspirin, clopidogrel and dipyridamole (and IIb/IIIa inhibitors)
      • Inherited disorders are rare

Idiopathic Thrombocytopenic Purpura

Background/Epidemiology

  • Mediated by autoantibodies, often against the membrane glycoprotein IIb/IIIa (sensitises platelets), which results in premature removal of platelets from the circulation by the reticulo-endothelial system.
    • This can occur with other immune conditions e.g. SLE or in malignancies e.g. B cell malignancies.  Also in pregnancy and with certain drug treatments
  • More common in women

Presentation

  • Usually presents insidiously with features of easy bruising, epistaxis, menorrhoea
    • Spontaneous bleeding (petechial rash) only occurs when platelet count is <20×10^9/l
    • Many cases discovered by chance after a FBC
  • In children, it commonly follows a viral infection.  Only 15-20% will go on to develop the chronic form.
  • Patients >65 should be investigated for symptoms/signs of B cell malignancy

Management

  • Only treat for persistent thrombocytopenia <30×10^9/l (except when there is increased risk of bleeding e.g. surgery) or for patients with spontaneous bleeding (usually both found together)
  • First line- prednisolone 1mg/kg/day
    • IVIg can be used in combination with steroid if there is haemostatic failure or a slow response to steroids
    • Persistent or potentially life-threatening thrombocytopenia (in any case) can be treated with platelet transfusion
  • If ITP relapses frequently, splenectomy can be considered
  • Rarely, thrombopoietin analogues e.g. romiplostin or thrombopoietin receptor agonists e.g. eltrombopag, can be considered.  Alternatively, steroid + immunosuppression can also be an option

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