Clinical syndrome in which a decreased number of circulating platelets manifests as a bleeding tendency, causing petechiae, ecchymoses, purpura and bleeding from venepuncture sites, nose etc., in an otherwise healthy patient

Aetiology

• May occur in isolation (primary ITP) or in association with other disorders (secondary)
• Causes of secondary ITP include:
  • Other autoimmune disorders (including antiphospholipid antibody syndrome and systemic lupus erythematosus)
  • Viral infections (including cytomegalovirus, varicella-zoster, hepatitis C and HIV)
  • Infection with Helicobacter pylori
  • Medication
  • Lymphoproliferative disorders

Pathophysiology

Caused by a type II hypersensitivity reaction:

• It is caused by the production of antibodies that target and destroy platelets
• This can happen spontaneously, or it can be triggered by something, such as a viral infection

Clinical features

• Usually present in children under 10 years old
• Often there is a history of a recent viral illness
• The onset of symptoms occurs over 24-48 hours:
  • Bleeding, for example from the gums, epistaxis or menorrhagia
  • Bruising
  • Petechial or purpuric rash, caused by bleeding under the skin

Investigations

• Bloods:
  • FBC: isolated thrombocytopenia
  • Blood film

• Bone marrow examination: only required if case appears atypical

Management

• Usually no treatment is required and patients are monitored until the platelets return to normal
• Around 70% of patients will remit spontaneously within 3 months
• Treatment may be required if the patient is actively bleeding or severe thrombocytopenia (platelets below 10):
  • Prednisolone
  • IV immunoglobulins
  • Blood transfusions if required
  • Platelet transfusions only work temporarily