Immune (Idiopathic) Thrombocytopenic Purpura

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder in which IgG autoantibodies against platelet surface antigens cause platelet destruction — mainly in the spleen — and also impair platelet production by megakaryocytes. It presents as isolated thrombocytopenia with an otherwise normal blood count and film.

Primary ITP has no underlying cause; secondary ITP is driven by a drug, another autoimmune disease (especially SLE), a lymphoproliferative disorder (e.g. CLL), or infection (HIV, hepatitis C, Helicobacter pylori). By duration it is newly diagnosed (< 3 months), persistent (3–12 months) or chronic (> 12 months).

Demographics: in children, usually acute and self-limiting, often triggered by a viral infection, with spontaneous recovery typically within 3 months.

In adults it is generally chronic, spontaneous remission is uncommon (under ~10%), and it is more common in women of reproductive age; the adult peak incidence is around age 60, where it affects men and women about equally. Adult incidence is roughly 1–6 per 100,000 per year.

Pattern: bruising + oral/mucosal bleeding + epistaxis → think ITP.

History

• Often asymptomatic, identified incidentally on a routine FBC.
• When symptomatic, mucocutaneous bleeding predominates: purpura and petechiae, epistaxis, bleeding gums, menorrhagia; fatigue is common.
• Gross gastrointestinal bleeding, haematuria and intracranial haemorrhage are uncommon but serious — the risk of major bleeding rises with a platelet count below 20×10⁹/L, older age, and prior bleeding.
• Ask about alcohol, drugs/medications, recent viral illness, and a history of autoimmune or lymphoproliferative disorders.

Examination

Splenomegaly is rare in ITP — its presence suggests another cause (or a coexisting condition such as viral infection or autoimmune haemolytic anaemia, i.e. Evans syndrome).

Look for purpura, petechiae (including on the palate) and ecchymoses; check for lymphadenopathy and hepatomegaly, which point away from ITP.

Investigations

FBC and blood film (large platelets, otherwise normal; the film also helps exclude TTP, inherited thrombocytopenia and leukaemia); HIV and hepatitis C serology (reversible causes); LFTs; coagulation studies.

Testing for Helicobacter pylori is worthwhile when there are dyspeptic symptoms, since eradication can remit the ITP. ANA and further autoimmune workup are added if features suggest SLE. Antiplatelet antibody testing is not routinely useful.

Bone marrow examination is not required for diagnosis — reserve it for atypical features, other blood-count abnormalities, or failure to respond to first-line therapy; when done it shows normal or increased megakaryocytes.

Overall, ITP remains a diagnosis of exclusion once the other causes of isolated thrombocytopenia have been ruled out.

Management

Children: usually supportive — most recover spontaneously. Observation is appropriate for no or minor bleeding regardless of the platelet count; glucocorticoids or IVIG are used for mucosal bleeding. Persistent, severe, symptomatic disease beyond ~6 months may warrant a TPO receptor agonist; splenectomy is rarely done and is deferred at least 12 months.

Adults: patients who are asymptomatic with a platelet count above 30×10⁹/L and no additional bleeding risk can simply be monitored. First-line treatment for bleeding or a count below 30×10⁹/L is a course of oral glucocorticoid (prednis(ol)one, or a short high-dose dexamethasone course); IVIG or IV anti-D immune globulin is added when a rapid rise is needed. Glucocorticoids should not be continued beyond about 6 weeks because of toxicity, and most patients relapse on tapering. Refer any active bleeding to the ED.

Second-line (chronic or refractory disease): thrombopoietin receptor agonists (TPO-RAs — eltrombopag, romiplostim, avatrombopag) achieve response rates over 85% and a proportion of patients later sustain a treatment-free remission; rituximab is a common steroid-sparing option (response ~57%, but many relapse by 5 years); fostamatinib (a spleen tyrosine kinase inhibitor) and rilzabrutinib (a BTK inhibitor) are newer oral options.

Splenectomy produces lasting remission in about two-thirds of steroid-relapsed patients but is now often avoided given its irreversibility and the long-term risk of thrombosis and infection with encapsulated organisms; it is usually deferred at least 12 months and preceded by pneumococcal, Haemophilus influenzae type b and meningococcal vaccination.

Life-threatening bleeding: combine platelet transfusion (only used for critical bleeding, not prophylactically) with IV immune globulin and/or IV glucocorticoid; IV anti-D is an option in Rh-positive, non-splenectomised patients; tranexamic acid is a useful adjunct.

Pregnancy: ITP tends to worsen but, with treatment, is not associated with increased maternal or fetal mortality.