Idiopathic thrombocytopenic purpura (ITP)

Overview

Idiopathic thrombocytopenic purpura (ITP), currently referred to as immune thrombocytopenia, is an acquired autoimmune haematological disorder characterized by isolated thrombocytopenia due to immune-mediated platelet destruction and reduced platelet production.

The diagnosis is primarily one of exclusion after ruling out secondary causes of thrombocytopenia.

ITP may occur as:

• Acute ITP:

  • More common in children.

  • Often self-limiting.

• Chronic ITP:

  • More common in adults.

  • Persists for more than 12 months.

Causes and associations

ITP may be associated with:

• Autoimmune disorders such as systemic lupus erythematosus (SLE).

• Viral infections including HIV and hepatitis C.

• Recent vaccination (rare association).

• Certain medications.

• Lymphoproliferative disorders.

Pathophysiology

ITP results from:

• Autoantibody-mediated platelet destruction.

• Increased platelet clearance by the spleen.

• Impaired platelet production due to immune effects on megakaryocytes.

Clinical presentation

Clinical features are mainly due to reduced platelet count.

Common features include:

• Long history of purpura.

• Petechiae.

• Easy bruising.

• Epistaxis.

• Gingival haemorrhage.

• Menorrhagia.

• Prolonged bleeding after minor trauma.

Severe complications:

• Intracerebral haemorrhage (rare but the most serious and potentially fatal complication).

Note:

• Overt bleeding is uncommon unless thrombocytopenia is severe (platelet count <10 × 10⁹/L).

• A palpable spleen strongly suggests that ITP is not the cause of thrombocytopenia.

Diagnostic criteria

ITP is a diagnosis of exclusion.

Criteria include:

• Isolated thrombocytopenia (platelet count <100 × 10⁹/L).

• Normal red blood cell and white blood cell morphology.

• Absence of splenomegaly.

• No evidence of secondary causes.

Investigations

Laboratory investigations

• Full blood picture (FBP/CBC):

  • Isolated thrombocytopenia.

• Peripheral blood smear:

  • Confirms thrombocytopenia.

  • Excludes platelet clumping or abnormal cells.

• Coagulation profile:

  • Usually normal.

• HIV screening.

• Hepatitis C screening.

• Autoimmune screening where clinically indicated.

Bone marrow examination

Usually not required unless:

• Patient is >60 years.

• Atypical features are present.

• There is failure to respond to treatment.

Management of Idiopathic thrombocytopenic purpura (ITP)

Management depends on:

• Platelet count.

• Severity of bleeding.

• Clinical condition.

Non-pharmacological management

Patients with platelet counts:

• 50 × 10⁹/L usually do not have spontaneous bleeding and may undergo invasive procedures.

General measures:

• Avoid antiplatelet drugs such as aspirin.

• Avoid NSAIDs.

• Educate patients regarding bleeding precautions.

• Regular platelet monitoring.

Emergency management

Acute bleeding caused by severe thrombocytopenia requires immediate platelet transfusion.

Pharmacological treatment

Corticosteroid therapy

For patients with platelet counts below 30 × 10⁹/L:

• Prednisolone PO 1 mg/kg/day for 3–6 weeks, then taper by 10 mg weekly.

OR

• Dexamethasone IV 40 mg in 500 ml normal saline running over 4 hours once daily for 4 days.

If no response

• Human immunoglobulin G IV 0.4 g/kg/day for 5 days.

OR

• Human immunoglobulin G IV 1 g/kg/day for 2 days followed immediately by platelet transfusion.

Splenectomy

Consider in patients who:

• Are refractory to corticosteroid therapy.

• Relapse after initial response.

Splenectomy reduces platelet destruction by removing the major site of antibody-mediated platelet clearance.

Prevention and monitoring

• Regular platelet monitoring.

• Avoid drugs that increase bleeding risk.

• Patient education regarding bleeding precautions.

• Vaccination before splenectomy:

  • Pneumococcal vaccine.

  • Meningococcal vaccine.

  • Haemophilus influenzae type b vaccine.

Complications

• Life-threatening bleeding including intracerebral haemorrhage.

• Adverse effects of long-term corticosteroid therapy.

• Post-splenectomy infections.

• Thromboembolic risk related to disease or treatment.

Prognosis

• Children often have self-limiting disease.

• Adults frequently develop chronic or relapsing disease.

• Mortality is low but increases with severe haemorrhagic complications.