Immune Thrombocytopenia (ITP)

Clinical Snapshot

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder in which antibodies directed against platelet surface glycoproteins cause both accelerated platelet destruction and, in many patients, an inappropriately blunted marrow production response. It is a diagnosis of exclusion: isolated thrombocytopenia (platelet count under 100 ×10⁹/L) in an otherwise well patient, with no other explanation identified. ITP is classified as primary (no underlying cause) or secondary (associated with another condition — systemic lupus erythematosus, chronic lymphocytic leukemia, HIV, hepatitis C, H. pylori infection, common variable immunodeficiency, or certain drugs), and by phase from diagnosis: newly diagnosed (0-3 months), persistent (3-12 months), and chronic (over 12 months).^[1] The single most important management principle is that bleeding risk does not track tightly with the platelet count — a stable patient with a very low count and only minor bruising may need no pharmacologic treatment at all, while treatment decisions are driven by the platelet count together with the pattern and severity of bleeding.

Recognize the Condition

Presentation ranges from an incidental low platelet count on routine bloodwork to overt mucocutaneous bleeding. "Wet" purpura — mucosal bleeding such as oral blood blisters, gum bleeding, or epistaxis — signals a materially higher near-term bleeding risk than "dry" purpura confined to the skin (petechiae, ecchymoses), and this distinction matters more for urgency than the platelet count alone.

Petechiae (pinpoint, non-blanching) and ecchymoses (bruising), often out of proportion to any trauma.
Epistaxis, gingival bleeding, and menorrhagia.
Oral mucosal blood blisters (wet purpura) — an important bleeding-risk marker.
Fatigue is common but nonspecific.
Splenomegaly and lymphadenopathy are not typical of primary ITP — their presence should prompt a search for a secondary cause instead.

Phases of ITP from diagnosis

Newly diagnosed (0-3 months)

Many adult patients respond to first-line corticosteroids; a substantial proportion of children resolve spontaneously within this window without needing treatment.

Persistent (3-12 months)

Platelet count has not achieved a durable response, or the patient remains steroid-dependent — second-line therapy is increasingly considered.

Chronic (over 12 months)

Disease has not remitted; management shifts toward durable second-line options, since prolonged corticosteroid use carries cumulative toxicity that outweighs its benefit at this stage.

Risk Factors

Recent viral infection, particularly in children — often precedes an acute, self-limited episode.
Underlying autoimmune disease — systemic lupus erythematosus, autoimmune thyroid disease, antiphospholipid syndrome.
Lymphoproliferative disorders — chronic lymphocytic leukemia, lymphoma.
Chronic infection — HIV, hepatitis C, and H. pylori (eradication can improve the platelet count in infected patients with ITP).
Common variable immunodeficiency.
Certain drugs associated with immune-mediated thrombocytopenia (a distinct entity from primary ITP) — quinine, vancomycin, sulfonamides, and some anticonvulsants.
Pregnancy — ITP can first present or worsen during pregnancy; gestational thrombocytopenia is a distinct, more common, and generally benign cause of mild thrombocytopenia in pregnancy that must be distinguished from it.
Recent vaccination — rare, usually mild and self-limited.

Red Flags & Refer

Escalate immediately for any of the following — the platelet count alone should never be the only factor determining urgency:

Any suspected intracranial, gastrointestinal, or other life-threatening hemorrhage — a hematologic and, where relevant, surgical emergency.
Wet purpura (oral blood blisters, gum bleeding) or significant epistaxis, especially with a platelet count under 20-30 ×10⁹/L.
Platelet count under 10 ×10⁹/L, regardless of current bleeding symptoms — spontaneous serious bleeding risk rises steeply below this level.
Features suggesting thrombotic thrombocytopenic purpura (fever, neurologic changes, renal dysfunction, schistocytes on smear) rather than ITP — this is a distinct hematologic emergency needing urgent plasma exchange, not corticosteroids; see the differential table in Assessment & Diagnosis.
Features suggesting a secondary cause needing its own workup — splenomegaly, lymphadenopathy, or unexplained abnormalities in the other blood cell lines.
A pregnant patient with severe thrombocytopenia or active bleeding — urgent combined obstetric/hematology management.
Relapse after first-line therapy, or no adequate response to first-line corticosteroids — refer to hematology for second-line planning rather than prolonging or repeating a steroid course.

Assessment & Diagnosis

Differentiating the causes of new thrombocytopenia

Parameter	Primary ITP	Heparin-induced thrombocytopenia	TTP / HUS	DIC	Pseudothrombocytopenia
Context	Isolated finding in an otherwise well patient; may follow a viral illness	Heparin exposure in the preceding 2 weeks, or within 24 hours if re-exposed within the preceding 100 days	Acutely unwell with neurologic changes, renal dysfunction, or fever	Sepsis, trauma, an obstetric emergency, or malignancy — a clinically obvious trigger	Incidental lab finding in an otherwise well patient
Onset	Variable, often gradual	Day 5-10 of a first heparin exposure; within 24 hours on re-exposure	Acute, rapidly progressive	Acute, tracking the underlying trigger	None — a sample-handling artifact
Platelet count pattern	Isolated thrombocytopenia; other cell lines normal	A fall of over 50% from baseline, rarely below 20 ×10⁹/L	Severe thrombocytopenia with microangiopathic hemolysis	Falling platelets with a prolonged PT/aPTT and low fibrinogen	Falsely low count only — the true count is normal
Peripheral smear	Normal morphology; large platelets may be seen	Normal platelet morphology	Schistocytes (fragmented red cells)	Schistocytes may be present; evidence of consumption	Platelet clumps or platelet satellitism around neutrophils
Key distinguishing test	Diagnosis of exclusion — no single confirmatory test	4Ts score plus an anti-PF4/heparin antibody immunoassay	Severely reduced ADAMTS13 activity	Prolonged PT/aPTT, low fibrinogen, elevated D-dimer	Repeat the count in a citrate (blue-top) tube — it normalizes
Predominant risk	Bleeding	Thrombosis — venous and arterial — despite the low platelet count	Microvascular thrombosis and organ ischemia	Both bleeding and thrombosis	None — not a true hematologic abnormality

History

Bleeding history — site, severity, and whether it is new or longstanding.
Full medication review, looking specifically for a new drug that could cause immune-mediated thrombocytopenia.
Recent infection, autoimmune symptoms, family history of thrombocytopenia, pregnancy status, recent vaccination, and alcohol intake.

Examination

Characterize the bleeding pattern (dry versus wet purpura). Splenomegaly or lymphadenopathy is atypical for primary ITP and should prompt evaluation for a secondary cause instead.

Laboratory evaluation

CBC with differential and a peripheral blood smear are mandatory — this both confirms isolated thrombocytopenia (other cell lines normal) and excludes pseudothrombocytopenia (repeat the count in a citrate tube if platelet clumping is seen) and other causes such as TTP (schistocytes) or leukemia (blasts).
ITP is a diagnosis of exclusion — no single test confirms it. Platelet antibody testing is not recommended given poor sensitivity and specificity.^[2]
Test for HIV, hepatitis C, and H. pylori — treating an identified infection can resolve secondary ITP.^[1]
Direct antiglobulin (Coombs) test if hemolysis is suspected (Evans syndrome — combined ITP and autoimmune hemolytic anemia).
Quantitative immunoglobulins, particularly in children, if common variable immunodeficiency is a consideration.
ANA if lupus is clinically suspected.
Bone marrow examination is not routinely required — reserve it for atypical features: involvement of other cell lines, abnormal cells on the smear, poor response to treatment, or an older patient being considered for splenectomy.^[2]

Treatment Targets

Achieve a hemostatically safe platelet count — generally over 20-30 ×10⁹/L, or higher before a procedure — rather than a normal count.
Stop active bleeding.
Avoid unnecessary treatment of asymptomatic patients with a safe platelet count.
Minimize treatment-related toxicity, particularly from prolonged corticosteroid use.
Where possible, achieve durable remission off treatment with second-line therapy rather than indefinite maintenance.

Choose Initial Treatment

Direct treatment rule

1st line — observation in adults with newly diagnosed ITP and a platelet count of at least 30 ×10⁹/L who are asymptomatic or have only minor mucocutaneous bleeding — do not start corticosteroids in this group.^[1]

1st line — corticosteroids for a platelet count under 30 ×10⁹/L, or clinically significant mucocutaneous bleeding at any count: prednisone 0.5-2 mg/kg/day, or dexamethasone 40 mg/day for 4 days if a faster response is the priority. Use a short course — 6 weeks or less — with a taper, not prolonged maintenance dosing.^[1]

Emergency — severe or life-threatening bleeding: IVIG 1 g/kg IV (may repeat the next day) or anti-D immune globulin (Rh(D)-positive, non-splenectomized patients only) combined with a corticosteroid, plus platelet transfusion for severe active bleeding — transfusion still works despite ongoing destruction and buys time for other therapies to take effect.

2nd line — relapse after steroid taper, steroid-dependence, or steroid-refractory disease: a TPO receptor agonist (eltrombopag or romiplostim) or rituximab — both are reasonable initial second-line choices; there is no strong head-to-head evidence favoring one class over the other, so patient preference (oral daily TPO-RA versus a finite infusion course of rituximab) is a legitimate factor.^[3]

Splenectomy is effective and can produce a durable remission without ongoing drug therapy, but is irreversible and carries infection risk — where the clinical situation allows, defer splenectomy at least 12 months from diagnosis to allow time for spontaneous or medical remission, and ensure pneumococcal, meningococcal, and H. influenzae type b vaccination at least 2 weeks beforehand.^[2]

Multi-refractory disease (failed corticosteroids and at least one second-line agent): fostamatinib, combination immunosuppression, or splenectomy — refer to hematology.

Non-Pharmacologic Treatment

Avoid antiplatelet agents, NSAIDs, and anticoagulants unless clearly necessary and the bleeding risk has been specifically weighed.
Avoid contact sports and other high bleeding-risk activities while significantly thrombocytopenic.
Complete pneumococcal, meningococcal, and H. influenzae type b vaccination at least 2 weeks before an elective splenectomy.
Patient education on bleeding precautions and when to seek urgent care (wet purpura, severe headache, or heavy bleeding of any kind).
Treat an identified underlying cause (e.g., H. pylori eradication, stopping a causative drug) alongside — or sometimes instead of — ITP-specific pharmacotherapy.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
Prednisone Preferred	1st-line corticosteroid	0.5-2 mg/kg/day PO, taper after response, total course 6 weeks or less	Hyperglycemia, insomnia, mood change, weight gain, osteoporosis with prolonged use	A short course is intended, not chronic maintenance — taper rather than stopping abruptly.
Dexamethasone Preferred	1st-line corticosteroid, when a faster response is the priority	40 mg PO/IV daily for 4 days; may repeat every 2 weeks for up to 3 cycles	Hyperglycemia, insomnia, GI upset, mood change	Pulsed dosing — no taper needed for the short pulse itself.
Immunoglobulin (human), IV Special situation	Emergency/rapid platelet rise, or steroid-sparing in pregnancy	1 g/kg IV once, may repeat the next day if needed	Headache, aseptic meningitis, renal dysfunction, thrombosis, hemolysis	Rapid but transient effect (days to weeks). Premedicate for infusion reactions and ensure adequate hydration.
Anti-D immune globulin Special situation	Emergency, Rh(D)-positive non-splenectomized patients only	50-75 mcg/kg IV once	Hemolysis (can be severe), fever, chills, rare DIC	Contraindicated in Rh-negative or splenectomized patients — relies on splenic Fc-receptor blockade. Monitor hemoglobin.
Eltrombopag Preferred	2nd line — TPO receptor agonist	25-50 mg PO daily, titrate to platelet response, maximum 75 mg/day	Hepatotoxicity, thrombosis, rebound thrombocytopenia on discontinuation	Take on an empty stomach; separate from polyvalent-cation products (antacids, dairy, mineral supplements) by several hours. Requires LFT monitoring.
Romiplostim Preferred	2nd line — TPO receptor agonist, weekly SC	1 mcg/kg SC weekly, titrate by 1 mcg/kg increments to target platelet count, maximum 10 mcg/kg	Headache, arthralgia, thrombosis, rare bone marrow reticulin fibrosis	Weekly clinic administration; dose is titrated to response, not fixed.
Rituximab Alternative	2nd line — B-cell depletion, off-label for ITP	375 mg/m² IV weekly for 4 doses	Infusion reactions, hepatitis B reactivation, rare PML, hypogammaglobulinemia	Screen hepatitis B serology before starting. Response can take several weeks and is not durable in every patient.
Fostamatinib Alternative	Later-line — spleen tyrosine kinase inhibitor	100 mg PO BID, may increase to 150 mg BID at 4 weeks if response is inadequate	Hypertension, diarrhea, hepatotoxicity, neutropenia	Monitor blood pressure and LFTs. Avoid with strong CYP3A4 inhibitors.

Special Populations

Pregnancy

Distinguish ITP from gestational thrombocytopenia, which is more common, milder (typically over 70-80 ×10⁹/L), has no prior history, and resolves postpartum. Treat if the platelet count is under 20-30 ×10⁹/L, there is bleeding, or a safe count is needed for delivery (thresholds vary by mode of anesthesia and delivery — coordinate with obstetric anesthesia). First-line treatment is a corticosteroid (prednisone is generally preferred over dexamethasone in pregnancy given less placental transfer) or IVIG. Avoid TPO receptor agonists and rituximab in pregnancy given limited safety data; anti-D is generally avoided as well. Check the neonatal platelet count after delivery given passive transplacental antibody transfer.

Breastfeeding

Corticosteroids and IVIG are compatible with breastfeeding. Data for TPO receptor agonists and rituximab are limited — specialist-directed decision.

Pediatrics

Most childhood ITP is self-limited, often following a viral illness, and resolves within 12 months without treatment. Favor observation over pharmacologic treatment even at low platelet counts if bleeding is minimal. When treatment is needed, a short corticosteroid course or IVIG is first-line. Avoid splenectomy under age 5 given infection risk, and defer it where possible until the chronic phase is clearly established. Romiplostim and eltrombopag are approved for refractory pediatric ITP down to 1 year of age.

Older adults

Bleeding risk at a given platelet count is higher than in younger patients, and corticosteroid toxicity (osteoporosis, hyperglycemia, psychiatric effects) is more consequential — favor shorter courses and earlier transition to a steroid-sparing second-line agent.

Hepatic impairment

Eltrombopag requires dose reduction in hepatic impairment (start at 12.5 mg/day) given hepatotoxicity risk and altered metabolism — monitor LFTs closely.

Monitoring & Follow-Up

Check platelet count frequently (often weekly) during active treatment, spacing out once stable. Use a structured assessment of bleeding symptoms at every visit, not the platelet count in isolation. Monitor corticosteroid-related toxicity — glucose, bone density with prolonged or repeated courses, mood/sleep effects. Check LFTs regularly with eltrombopag or fostamatinib. Screen for thrombosis-related symptoms with any TPO receptor agonist. Confirm vaccination status well before any planned splenectomy. Reassess for a secondary cause if the clinical course is atypical or the response to standard therapy is unexpectedly poor.

Treatment Failure / Next Step

Confirm the diagnosis is still correct — repeat the smear, exclude pseudothrombocytopenia, and reconsider TTP or a secondary cause if not already excluded.
Confirm adherence to the corticosteroid regimen and appropriate dose/duration before labeling it a steroid failure.
For relapse after a steroid taper, or steroid-dependence: move to a TPO receptor agonist, rituximab, or fostamatinib rather than repeating or prolonging corticosteroids.
For failure of one second-line agent: switch class (for example, a TPO receptor agonist to rituximab, or vice versa) rather than assuming every second-line option will fail.
For multi-refractory ITP: refer for splenectomy evaluation or combination therapy under specialist direction, and reconsider a secondary-ITP workup (bone marrow examination, expanded serologies) if not already done.
For emergency bleeding unresponsive to IVIG and corticosteroids: give a platelet transfusion (effective despite ongoing destruction), consider an antifibrinolytic (tranexamic acid), and obtain urgent hematology consultation.

Common Errors to Avoid

Treating an asymptomatic adult with a platelet count of at least 30 ×10⁹/L with corticosteroids instead of observing.
Continuing corticosteroids beyond about 6 weeks as maintenance therapy instead of tapering and moving to a steroid-sparing second-line agent.
Giving anti-D to an Rh-negative or previously splenectomized patient.
Missing a hepatitis B screen before starting rituximab.
Not counselling on the empty-stomach and mineral-separation requirement for eltrombopag, leading to reduced absorption and apparent treatment failure.
Basing the decision to treat on the platelet count alone without considering actual bleeding symptoms and disease phase.
Missing a drug cause of thrombocytopenia (for example, vancomycin or quinine) and treating it as primary ITP instead of stopping the causative agent.
Confusing ITP with heparin-induced thrombocytopenia in a patient with recent heparin exposure — a different mechanism requiring different treatment.
Missing TTP (schistocytes, neurologic or renal findings) and managing it as ITP — a delay in plasma exchange is life-threatening.

Clinical Decision Algorithm

Initial management of newly diagnosed adult ITP

Isolated thrombocytopenia confirmed on repeat CBC and smear; other causes excluded

Life-threatening bleeding, or platelet count under 10 ×10⁹/L with any bleeding

Emergency: IV corticosteroid plus IVIG (or anti-D if Rh-positive and non-splenectomized), plus platelet transfusion for severe bleeding — admit and involve hematology immediately

No severe bleeding

Assess platelet count and bleeding severity

Platelet count at least 30 ×10⁹/L, asymptomatic or minor bruising only

Observe — no pharmacologic treatment; recheck the platelet count periodically

Platelet count under 30 ×10⁹/L, or clinically significant mucocutaneous bleeding

Start prednisone 0.5-2 mg/kg/day, or dexamethasone 40 mg/day for 4 days if a faster response is needed

Taper over a short course (6 weeks or less); reassess the platelet response

Relapse or steroid-refractory ITP

Platelet count falls again during or after the steroid taper, or there is no adequate response to first-line corticosteroids

Confirm the diagnosis is still correct and exclude a secondary cause before escalating

Prefers ongoing medical therapy

Start a TPO receptor agonist (eltrombopag or romiplostim) or rituximab

Prefers durable remission off therapy

Consider splenectomy — typically deferred at least 12 months from diagnosis where the clinical situation allows

Multi-refractory disease

Refer to hematology for fostamatinib, combination therapy, or a clinical trial

Drug Tables

How to use this table: doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page.

Corticosteroids

First-line for symptomatic ITP or a platelet count under 30 ×10⁹/L; use a short course, not chronic maintenance.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Prednisone	Initial: 0.5-2 mg/kg/day PO Course length: 6 weeks or less, then taper	Hyperglycemia, insomnia, mood change, weight gain, dyspepsia; osteoporosis and adrenal suppression with prolonged/repeated use	Additive hyperglycemia with other diabetogenic drugs	Preferred for most patients; taper over the treatment course rather than stopping abruptly.
Dexamethasone	Pulse: 40 mg PO/IV daily x4 days Repeat cycles: May repeat every 2 weeks, up to 3 cycles	Hyperglycemia, insomnia, GI upset, mood change	Additive hyperglycemia with other diabetogenic drugs	Preferred when a faster response is the priority; no taper needed for the pulse itself.

Immune globulin products

Reserved for emergency bleeding or when a rapid platelet rise is needed (for example, before an urgent procedure or in pregnancy).

Drug	Dosage	Adverse effects	Drug interactions	Comments
Immunoglobulin (human), IV	Adults: 1 g/kg IV once; may repeat the next day if needed	Headache, aseptic meningitis, renal dysfunction (especially sucrose-containing formulations), thrombosis, hemolysis	Live vaccine response may be blunted for a period after IVIG	Effect is rapid but transient (days to weeks). Premedicate for infusion reactions; ensure adequate hydration.
Anti-D immune globulin	Adults: 50-75 mcg/kg IV once	Hemolysis (can be severe), fever, chills, rare DIC	None specific	Rh(D)-positive, non-splenectomized patients only — relies on splenic Fc-receptor blockade. Monitor hemoglobin closely.

Thrombopoietin receptor agonists (TPO-RAs)

Preferred 2nd-line option for relapsed, steroid-dependent, or steroid-refractory disease.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Eltrombopag	Adults, initial: 25-50 mg PO daily Titration: Adjust to platelet response, maximum 75 mg/day Hepatic impairment: Start 12.5 mg/day	Hepatotoxicity, thrombosis, cataracts (reported in pediatric long-term use), rebound thrombocytopenia on discontinuation	Chelates with polyvalent cations (antacids, calcium, iron, zinc) — separate by several hours; may increase statin exposure	Take on an empty stomach. Requires baseline and periodic LFT monitoring. Reduce the dose in hepatic impairment.
Romiplostim	Adults, initial: 1 mcg/kg SC weekly Titration: Increase by 1 mcg/kg increments to target platelet response, maximum 10 mcg/kg	Headache, arthralgia, thrombosis, rare bone marrow reticulin fibrosis	None significant	Weekly SC administration in a clinic setting; dose is titrated by response.

B-cell-depleting and other second-line immunomodulating agents

Alternatives to a TPO-RA, or used sequentially after TPO-RA failure.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Rituximab	Adults: 375 mg/m² IV weekly x4 doses	Infusion reactions, hepatitis B reactivation, rare progressive multifocal leukoencephalopathy, hypogammaglobulinemia	Avoid live vaccines during and after treatment per the product monograph interval	Screen hepatitis B serology before starting. Response can take several weeks and is not durable in every patient.
Mycophenolate mofetil	Adults: 500-1000 mg PO BID	GI upset, myelosuppression, increased infection risk	Antacids, iron, and cholestyramine reduce absorption; avoid live vaccines	Slower onset (weeks); used more often in refractory or secondary ITP than as a first second-line choice.
Danazol	Adults: 200 mg PO BID-TID	Virilization, hepatotoxicity, dyslipidemia, weight gain	May increase warfarin's anticoagulant effect	Avoid in pregnancy given androgenic effects. Response may take several months to become apparent.
Azathioprine	Adults: 1-2.5 mg/kg/day PO	GI upset, hepatotoxicity, myelosuppression, increased infection risk	Allopurinol markedly increases toxicity — reduce the azathioprine dose substantially if co-prescribed; may reduce warfarin's anticoagulant effect	An alternative steroid-sparing option; slow onset over several months.

Spleen tyrosine kinase (SYK) inhibitor

A later-line oral option after other second-line therapies.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Fostamatinib	Initial: 100 mg PO BID Titration: Increase to 150 mg BID at 4 weeks if response is inadequate	Hypertension, diarrhea, hepatotoxicity, neutropenia	Avoid with strong CYP3A4 inhibitors; monitor closely with strong CYP3A4 inducers	Monitor blood pressure and LFTs regularly during treatment.

Evidence note: drug inventory, dosing, adverse effects, and comments reflect standard Canadian practice, cross-checked against current ASH guidance.^[1]

References

American Society of Hematology 2019 guidelines for immune thrombocytopenia — Blood Advances, American Society of Hematology (Neunert C, Terrell DR, Arnold DM, et al.). Blood Adv 2019;3(23):3829-3866
Updated international consensus report on the investigation and management of primary immune thrombocytopenia — Blood Advances, American Society of Hematology (Provan D, Arnold DM, Bussel JB, et al.). Blood Adv 2019;3(22):3780-3817
The 2022 review of the 2019 American Society of Hematology guidelines on immune thrombocytopenia — Blood Advances, American Society of Hematology (Neunert CE, Arnold DM, Grace RF, Kuhne T, McCrae KR, Terrell DR). Blood Adv 2024;8(13):3578-3582

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.