Hematology, Oncology & Immunology · Topic 9 of 26

Immune Thrombocytopenia (ITP)

Hematology · immune platelet destruction

Immune Thrombocytopenia (ITP)

Isolated low platelets, normal smear, other causes excluded; treat below 30,000 with corticosteroids, now paired with rituximab or a TPO agent.

Key numbers

Isolated low platelets, normal smear otherwisePlt < 100,000/mcL

Treat when platelets fall below 30,000Treat if < 30,000/mcL

01 · Defined byIsolated low platelets, normal smear otherwise

ITP is a diagnosis of exclusion: isolated thrombocytopenia (usually below 100,000/mcL) with an otherwise normal blood count and smear, after drugs, infection and other diseases are ruled out.

02 · The ruleTreat when platelets fall below 30,000

Newly diagnosed adults with platelets below 30,000/mcL, even without symptoms or with only minor bleeding, are treated; with 30,000/mcL or more and no bleeding, observe rather than give corticosteroids.

03 · GiveSteroids first: dexamethasone or prednisone

Corticosteroids are the backbone of initial therapy: dexamethasone 40 mg daily for 4 days or prednisone 0.5–2 mg/kg/day, limited to 6 weeks or less; platelets usually rise within 2–5 days.

Causes & risk factors

Why it happens

Look for secondary ITP and drug causesSecondary immune thrombocytopenia occurs with HIV, hepatitis C, lupus, antiphospholipid syndrome and CLL; drug-induced thrombocytopenia looks identical except for the medication history.

Presentation

What you'll see

Petechiae and mucosal bleeding; spleen normalITP bleeding is mucocutaneous — petechiae, purpura, epistaxis, gum and menstrual bleeding; the spleen is normal in size, so splenomegaly points to another diagnosis.

Do right now

In this order

First moves

Smear, HIV and hepatitis C tests; marrow rarely

→

Treat when platelets fall below 30,000Treat if < 30,000/mcL

→

Steroids first: dexamethasone or prednisone

→

Initial therapy: steroids plus rituximab or TPO agent

Why each step

Smear, HIV and hepatitis C tests; marrow rarelyWork-up: review the smear (exclude clumping, schistocytes, blasts), medications, alcohol, coagulation studies, liver tests, HIV and hepatitis C; bone marrow is not needed unless features are atypical or therapy fails.

Treat when platelets fall below 30,000Newly diagnosed adults with platelets below 30,000/mcL, even without symptoms or with only minor bleeding, are treated; with 30,000/mcL or more and no bleeding, observe rather than give corticosteroids.

Steroids first: dexamethasone or prednisoneCorticosteroids are the backbone of initial therapy: dexamethasone 40 mg daily for 4 days or prednisone 0.5–2 mg/kg/day, limited to 6 weeks or less; platelets usually rise within 2–5 days.

Initial therapy: steroids plus rituximab or TPO agentASH 2026 suggests starting corticosteroids (± IVIG) together with rituximab or a thrombopoietic agent rather than corticosteroids alone; steroids alone remain the choice when neither is available.

Management

Orders

Critical bleed: steroids, IVIG, platelets, TXA together must knowFor a critical ITP bleed (intracranial or causing instability), give everything at once: high-dose corticosteroids (methylprednisolone 1 g IV daily), IVIG 1 g/kg, platelet transfusion, tranexamic acid and a thrombopoietin receptor agonist.

Second line: TPO receptor agonist or rituximabIf more treatment is needed after corticosteroids, ASH recommends a thrombopoietic agent (romiplostim, eltrombopag, avatrombopag) or suggests rituximab; if those are declined or unsuitable, a BTK inhibitor, mycophenolate or a SYK inhibitor.

IVIG 1 g/kg for a fast riseIVIG 1 g/kg daily for 1–2 days raises platelets within 2–4 days, but the effect lasts only 2–4 weeks; use it for bleeding or before procedures, not for maintenance.

Anti-D only if Rh-positive with a spleenIV anti-D immune globulin (75 mcg/kg) works only in Rh-positive patients who still have a spleen and can cause severe intravascular hemolysis and DIC.

Splenectomy: wait 1 year, vaccinate firstReserve splenectomy for patients failing multiple therapies, delaying it at least 1 year from diagnosis when feasible; vaccinate against pneumococcus, Haemophilus influenzae and meningococcus at least 2 weeks before.

The rules

Know these

New ITP below 20,000: admitAdmit newly diagnosed adults with platelets below 20,000/mcL even if asymptomatic or with minor bleeding; patients with established ITP and counts of 20,000/mcL or more can be managed as outpatients.

Platelet transfusion only for life-threatening bleedingTransfused platelets are destroyed quickly in ITP: give them only for life-threatening, CNS or ocular bleeding, together with IVIG and corticosteroids — never prophylactically.

ITP or TTP?

Commonly confused

Smear	Normal red and white cells; few, large platelets
Hemolysis	None
Main danger	Mucocutaneous bleeding
Treatment	Corticosteroids ± IVIG, rituximab or a TPO agent; platelets only for critical bleeding

More detail

Reference

Show 6 reference facts

Adult ITP is usually chronic — spontaneous remission occurs in fewer than 10% — whereas most children remit spontaneously within weeks to months and are usually observed.

TPO receptor agonists (romiplostim 1–10 mcg/kg SC weekly, eltrombopag 25–75 mg daily, avatrombopag 20–40 mg daily) respond in more than 85% but often need continuous use.

Rituximab is most often given 375 mg/m² IV weekly for 4 doses; responses are frequent but only about 21% of adults remain in remission at 5 years.

Despite low platelets, ITP carries an increased risk of thrombosis; splenectomy adds risks of thrombosis and infection with encapsulated bacteria.

For a critical ITP bleed, recombinant factor VIIa is not recommended because of thrombosis risk; urgent splenectomy is an option when other treatments fail.

In ITP the immature platelet fraction and mean platelet volume are often raised (large platelets on the smear), reflecting increased turnover.

Pearl

ITP is a diagnosis you earn by excluding everything else — the smear is normal apart from too few, often large, platelets.

Sources · Merck Manual Professional — Immune Thrombocytopenia (ITP) (Jun 2026) · ASH 2026 Guidelines for ITP: Initial and Second-Line Therapy in Adults with Primary ITP — summary of changes from 2019 · ASH 2026 ITP guideline teaching slide set (Cuker A et al., initial and second-line therapy in adults with primary ITP) · Neunert C et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Adv 2019;3(23):3829–3866 · Chowdhury SR et al. Guideline on the emergency management of critical bleeding in patients with immune thrombocytopenia. Blood Adv 2026;10:5558–5575 · Gauer RL, Whitaker DJ. Thrombocytopenia: Evaluation and Management. Am Fam Physician 2022;106(3):288–298 · Merck Manual Professional — Overview of Platelet Disorders (smear findings, transfusion in platelet destruction) · Merck Manual Professional — Thrombocytopenia: Other Causes · Merck Manual Professional — Thrombotic Thrombocytopenic Purpura (TTP) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).