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Immune Thrombocytopenia

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Overview

Formerly known as idiopathic thrombocytopenic purpura, immune thrombocytopenia (ITP) is an autoimmune condition leading to the destruction of platelets. It is no longer called idiopathic thrombocytopenic purpura because it is now known it has an autoimmune cause.

Other causes of ITP may be:

ITP also often occurs in children following a viral illness or immunisation and has a more abrupt onset. In children, ITP is self-limiting and often resolves after 6-8 weeks.

Epidemiology

  • Mean age of onset is around 5-6 years
  • Affects around 5 per 100,000 children per year
  • Another peak of incidence is in people >65 years
  • Women are affected more

Risk Factors

  • Age <10 or age >65
  • Female sex

Example History

A 25-year-old woman has bruising and an episode of a prolonged nosebleed. She feels generally well and has not had any fatigue, weight loss, night sweats, or fevers. On examination, there are small bruises on her legs.

Investigations:

Platelets:45 x 109/L(150 – 450 x 109/L)

Presentation

Patients may have:

  • Bleeding and bruising and petechiae/purpura
  • Epistaxis/gingival bleeding
  • No systemic symptoms (such as fevers/night sweats/weight loss)
  • No hepatosplenomegaly
  • No lymphadenopathy

Differential Diagnoses

Thrombotic thrombocytopenic purpura (TTP)

  • In TTP, patients usually have fevers and neurological symptoms
  • FBC shows anaemia alongside thrombocytopenia
  • Blood film shows schistocytes due to haemolysis
  • Lactate dehydrogenase is elevated and haptoglobins are low due to haemolysis

Heparin-induced thrombocytopenia (HIT)

  • There is a history of heparin use
  • Patients may have venous thromboembolisms
  • Blood tests are positive for HIT antibodies and HIT functional assays are positive

Gestational thrombocytopenia

  • The degree of thrombocytopenia is less severe, usually no lower than 70 x 109/L
  • Usually occurs late in gestation and recovers completely after delivery

Disseminated intravascular coagulation (DIC)

  • Patients are usually severely unwell e.g. sepsis/malignancy
  • FBC shows schistocytes due to haemolysis
  • PT and APTT are prolonged
  • D-dimer is elevated
  • Fibrinogen is decreased
  • Fibrinogen degradation products are increased

Investigations

All patients

  • Full blood count (FBC):
    • Thrombocytopenia is seen
  • Blood film:
    • No evidence of cell abnormalities (e.g. schistocytes, myelodysplasia etc.)
  • Bone marrow examination:
    • Only performed if atypical features are present (e.g. blood film abnormalities or features such as lymphadenopathy or splenomegaly)

Management

In adults

  • 1st-line: oral prednisolone
  • Consider normal human immunoglobulin (IVIG) if a rapid rise in platelet count is required (e.g. an acute severe haemorrhage)

In children

  • 1st-line: observe and monitor
  • If the platelet count is very low/significant bleeding, consider oral corticosteroids or IV IG 

Complications

  • Severe bleeding

Prognosis

  • Around 80% of children completely recover in 6 months
  • Adolescents and adults are more likely to develop chronic ITP

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