Blood & Lymphoreticular

Immune thrombocytopenia: adult diagnosis and treatment

Clinical Overview and When to Suspect ITP

— Incidence ~3.3 per 100,000 adults/year; bimodal — young women and adults >60.

— Female predominance under age 60; equalizes in older adults.

— Isolated low platelets with normal Hgb, WBC, and smear (aside from low platelets, occasional large platelets).

— Mucocutaneous bleeding: petechiae, purpura, epistaxis, gingival bleeding, menorrhagia.

— No splenomegaly, no lymphadenopathy, no constitutional symptoms.

— Recent viral illness, new drug, vaccination, or autoimmune background (SLE, antiphospholipid).

Board pearl: ITP is a diagnosis of exclusion. There is no confirmatory test — antiplatelet antibody assays have poor sensitivity/specificity and are not routinely recommended (ASH 2019).

— Platelets >30 ×10⁹/L and asymptomatic → often observation alone.

— Platelets <30 or active bleeding → treatment indicated.

— Platelets <10 → high risk of spontaneous serious bleeding including intracranial hemorrhage (~0.5%/yr in chronic ITP, higher in elderly).

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder defined by isolated thrombocytopenia (platelets <100 ×10⁹/L) in the absence of other causes, driven by antiplatelet autoantibodies (often anti-GPIIb/IIIa, anti-GPIb/IX) plus impaired megakaryocyte platelet production.

Adult ITP is typically insidious and chronic (>12 months in ~60–70%), in contrast to pediatric ITP which is often acute, post-viral, and self-limited.

Epidemiology:

When to suspect ITP on Step 3 stems:

Primary vs secondary ITP (20% of cases): triggered by HIV, HCV, H. pylori, SLE, CLL/lymphoma, CVID, drugs, post-vaccination. Always screen secondary causes before labeling primary.

Severity framework:

Practical Step 3 framing: a previously well 35-year-old woman with bruising and platelets of 18, normal WBC/Hgb, normal smear → think ITP first, then exclude secondary causes before pulling the trigger on therapy.

Presentation Patterns and Key History

— Duration: newly diagnosed (<3 mo), persistent (3–12 mo), chronic (>12 mo).

— Drug exposures: heparin (HIT — different mechanism, thrombosis not bleeding), quinine/quinidine, sulfonamides (TMP-SMX), vancomycin, linezolid, valproate, GPIIb/IIIa inhibitors, checkpoint inhibitors, PPIs, alcohol.

— Infections: HIV, HCV, HBV, H. pylori, CMV, EBV, recent COVID-19 or vaccination (rare association).

— Autoimmune symptoms: rash, arthralgia, sicca, Raynaud → SLE/APS overlap.

— Family history: to exclude inherited thrombocytopenias (MYH9, Bernard–Soulier) — these often have lifelong mild thrombocytopenia and large platelets on smear.

— Transfusion / pregnancy / travel history, dietary deficiency (B12/folate), recent live vaccines.

— Skin only (petechiae, bruises) — low grade.

— Mucosal (wet purpura, GI, GU, epistaxis lasting >10 min) — moderate, often treat.

— Organ (intracranial, retinal, severe GI) — emergency.

Key distinction: Isolated thrombocytopenia with fever, neuro symptoms, and hemolysis is TTP, not ITP — don't transfuse platelets, start plasma exchange.

Classic adult ITP vignette: previously healthy adult presents with petechiae on dependent surfaces (lower legs), wet purpura (oral mucosal blood blisters — ominous sign), easy bruising, epistaxis, or heavy menses; otherwise feels well.

Bleeding severity correlates loosely with platelet count, but patients >60 bleed more at any given count — incorporate age into urgency.

History elements that drive Step 3 reasoning:

Bleeding score (IWG/ITP-BAT) considerations:

Menstrual history is high yield: ITP can present as menorrhagia in young women; ask about pad count, clots, iron deficiency anemia.

Ask specifically about headache, vision change, focal deficits in any ITP patient with platelets <20 — these screen for intracranial bleed and change disposition immediately.

Document functional status and fall risk in older adults: it changes treatment threshold for therapy initiation.

Physical Exam Findings and Bleeding Assessment

— Petechiae: pinpoint, non-blanching, often on ankles/shins (gravity-dependent), oral palate.

— Purpura and ecchymoses without trauma history.

— Wet purpura: hemorrhagic bullae on buccal mucosa, tongue, palate → marker of severe thrombocytopenia and higher risk of intracranial hemorrhage; treat urgently.

— Active epistaxis, gingival oozing after brushing, conjunctival hemorrhage.

— Splenomegaly → think lymphoma, CLL, cirrhosis, infiltrative disease.

— Lymphadenopathy → lymphoproliferative disease, HIV.

— Hepatomegaly, stigmata of chronic liver disease → cirrhosis with hypersplenism.

— Pallor out of proportion to bleeding → marrow failure, leukemia, MDS.

— Skeletal tenderness, gum hypertrophy → acute leukemia.

— Joint or skin findings of SLE → secondary ITP.

— Most ITP patients are hemodynamically stable; tachycardia or hypotension implies significant blood loss (often GI or GYN) and demands resuscitation.

— Neuro exam in every patient with platelets <20: pupils, GCS, focal deficits, fundoscopy if available.

CCS pearl: In a CCS case, in an ITP patient with new severe headache or any focal neuro finding, order non-contrast head CT immediately, type & crossmatch, platelet transfusion, IVIG, and high-dose steroids in parallel — don't sequence them.

Adult ITP exam is deliberately unimpressive apart from bleeding signs — this is itself diagnostic.

Skin and mucosa:

What should NOT be present in primary ITP (their presence pushes you toward an alternative diagnosis):

Vital signs and hemodynamic assessment:

Practical bedside grading: count petechiae per body region, photograph wet purpura, and reassess every 12–24 hours during admission — trend matters as much as the absolute count.

In women, pelvic exam if menorrhagia is severe to evaluate bleeding source and exclude structural cause.

Diagnostic Workup — Initial Labs and Smear

— Confirms low platelets (rule out pseudothrombocytopenia from EDTA-induced clumping → repeat in citrate or heparin tube).

— Platelets may appear large (young, reticulated) — consistent with peripheral destruction.

— Schistocytes → TTP/HUS/DIC, NOT ITP.

— Blasts → acute leukemia.

— Teardrops, nucleated RBCs → marrow infiltration/myelofibrosis.

— Hypogranular neutrophils, Pelger-Huet → MDS.

Board pearl: Antiplatelet antibody testing and TPO levels are NOT recommended for routine diagnosis — they delay care and rarely change management. ITP remains clinical/exclusionary.

Key distinction: Isolated low platelets + normal smear + normal coags = ITP; add schistocytes + AKI + neuro = TTP — totally different treatment pathway (PLEX, steroids, caplacizumab).

CBC with differential: isolated thrombocytopenia. Hgb and WBC must be normal for primary ITP; if cytopenias in another lineage exist, broaden the workup.

Peripheral blood smear is mandatory and arguably the single most important test:

Reticulocyte count, LDH, haptoglobin, indirect bilirubin to exclude microangiopathic hemolysis.

Coags (PT/INR, aPTT, fibrinogen, D-dimer): normal in ITP; abnormal suggests DIC or liver disease.

Comprehensive metabolic panel: assess renal/hepatic function; abnormal LFTs hint at viral hepatitis or cirrhosis.

HIV and HCV serologies are recommended in all newly diagnosed adults (ASH 2019). Consider HBV before immunosuppression.

H. pylori testing (stool antigen or urea breath test) — particularly in endemic regions or with GI symptoms; eradication can raise platelet counts.

Quantitative immunoglobulins to screen for CVID (especially before splenectomy or rituximab).

TSH (autoimmune thyroid disease frequently coexists).

ANA, antiphospholipid antibodies if clinical suspicion or recurrent/refractory ITP — APS-associated ITP changes management (avoid splenectomy enthusiasm).

Blood type and direct antiglobulin test (DAT) if anti-D therapy considered (Rh-positive, non-splenectomized only).

Pregnancy test in reproductive-age women — alters therapy choice.

Diagnostic Workup — Advanced and Confirmatory Studies

— Atypical features: additional cytopenias, abnormal smear (blasts, dysplasia, teardrops), unexplained organomegaly/adenopathy, constitutional symptoms.

— Failure to respond to first-line therapy (steroids ± IVIG).

— Before splenectomy in some practices, though no longer mandatory.

— Suspicion of MDS, aplastic anemia, lymphoma, leukemia, marrow infiltration.

— Flow cytometry of peripheral blood if lymphocytosis or suspected CLL.

— SPEP/UPEP, free light chains if older with anemia, renal dysfunction.

— Antinuclear and antiphospholipid panel (lupus anticoagulant, anti-β2GP1, anticardiolipin) — present in 30–40% of chronic ITP; high-titer triple positivity changes thrombotic risk.

— Genetic testing for inherited thrombocytopenia if lifelong history, family history, large platelets, hearing loss, renal disease, or refractory to standard ITP therapy. Common entities: MYH9-related disorders, Bernard–Soulier, WAS, ANKRD26, congenital amegakaryocytic thrombocytopenia.

— Helicobacter pylori testing (eradicate if positive — can produce durable platelet response in 20–50%).

— CMV/EBV PCR in atypical or refractory cases.

— TPO level is occasionally used in research/refractory cases to distinguish production failure (high TPO) from peripheral destruction (low/normal TPO) — not routine.

Step 3 management: A 70-year-old with isolated thrombocytopenia, no atypical features, does not need a bone marrow before treatment — start prednisone or dexamethasone after initial workup. Reserve marrow for refractory disease or atypical features.

Bone marrow biopsy is not required for diagnosis in a typical adult ITP presentation, regardless of age (ASH 2019 update reversed older "always biopsy if >60" teaching).

Indications to proceed with bone marrow:

Expected ITP marrow: normal or increased megakaryocytes, otherwise unremarkable cellularity and morphology.

Other targeted studies based on clues:

Document in the chart: "Diagnosis of primary ITP based on isolated thrombocytopenia, normal smear, negative HIV/HCV serologies, no medication trigger, and absence of features suggesting secondary cause." That clinical documentation is the diagnostic "test."

Reassess the diagnosis at every relapse — secondary causes (lymphoma, HIV seroconversion, drug exposure) can emerge later.

Treatment Thresholds and First-Line Management Logic

— Activity counseling: avoid contact sports, avoid NSAIDs/aspirin, fall prevention.

— Platelet count <30 ×10⁹/L, even if asymptomatic (ASH 2019 conditional recommendation).

— Any clinically significant bleeding regardless of count.

— Procedure, surgery, pregnancy delivery, anticoagulation requirement, occupation/activity-related bleeding risk.

— Dental cleaning: ≥30.

— Minor surgery / dental extraction: ≥50.

— Major surgery: ≥80.

— Neurosurgery / posterior eye surgery: ≥100.

— Vaginal delivery: ≥50; epidural/neuraxial anesthesia: ≥70–80; cesarean: ≥50–80.

— Corticosteroids are standard. Options:

– Dexamethasone 40 mg PO daily × 4 days (1–3 cycles, q14–28 days) — faster response, possibly better sustained response.

– Prednisone 0.5–2 mg/kg/day (typically 1 mg/kg) × 1–2 weeks, then taper over 4–8 weeks — do not continue >6–8 weeks.

— IVIG 1 g/kg × 1–2 days or anti-D (50–75 µg/kg) is added when rapid rise is needed (active bleeding, surgery, pregnancy) — works in 24–48 h.

Board pearl: Initial response rates to steroids ~70–80%, but sustained remission only ~20–30% at 1 year — most adult ITP becomes chronic.

CCS pearl: For a stable outpatient with platelets 20 and only mild bruising, the right CCS sequence is: counsel/precautions → dexamethasone 40 mg × 4 days → recheck CBC in 1 week → hematology follow-up in 2 weeks. Don't admit; don't transfuse.

Treatment is driven by bleeding and platelet count, modified by patient factors — not by platelet count alone.

Asymptomatic patients with platelet count ≥30 ×10⁹/L generally need no treatment — observation with serial CBCs.

Treat when:

Target platelet counts for procedures:

First-line outpatient therapy for newly diagnosed adults:

Avoid prolonged steroid courses — toxicity outweighs benefit. If no durable response after 6–8 weeks, move to second-line therapy.

Pharmacotherapy — Second-Line and Beyond

— Eltrombopag (PO daily, on empty stomach, avoid dairy/cation chelation; monitor LFTs).

— Romiplostim (SC weekly).

— Avatrombopag (PO with food; no LFT or dietary restrictions — increasingly preferred).

— Response 60–90%; risk of rebound thrombocytopenia on discontinuation; thrombosis risk (~6%), marrow reticulin fibrosis (mild, reversible), hepatotoxicity (eltrombopag).

— Often used long-term; taper attempts after sustained response >6 months.

— Response ~60%, durable in ~20–30% at 5 years.

— Screen and treat HBV before infusion; give vaccinations before therapy when possible.

— Avoid in active infection, pregnancy.

— Most durable response (60–70% long-term remission) but irreversible and infection risk.

— Defer at least 12 months after diagnosis if possible.

— Pre-splenectomy vaccines ≥2 weeks before: pneumococcal (PCV15/20 + PPSV23), meningococcal (ACWY + B), Hib.

— Lifelong infection vigilance; consider daily penicillin in some patients post-op.

Key distinction: TPO-RAs stimulate platelet production; rituximab and splenectomy reduce destruction. A patient with marrow stress (recent chemo, pregnancy, HCV) may favor TPO-RA logic.

Step 3 management: Patient relapses 2 months after dex taper with platelets of 12 and mucosal bleeding → restart steroids + IVIG for acute control, refer to hematology, initiate TPO-RA or rituximab as second-line; do not jump to splenectomy before 12 months.

Indications to advance beyond steroids: steroid dependence (requiring >5–10 mg prednisone equivalent to maintain count), steroid intolerance, failure to achieve durable response, or relapse.

Major second-line options (ASH 2019: prefer TPO-RAs or rituximab over splenectomy in the first year, allowing time for spontaneous remission):

Thrombopoietin receptor agonists (TPO-RAs):

Rituximab 375 mg/m² weekly × 4:

Fostamatinib (Syk inhibitor): PO BID, response ~40%; useful in refractory disease. Monitor BP, LFTs, diarrhea.

Splenectomy:

Other agents: mycophenolate, azathioprine, cyclosporine, danazol, dapsone, vincristine — for refractory/relapsed.

Acute and Life-Threatening Bleeding Management

— IV methylprednisolone 1 g/day × 3 days (or high-dose dexamethasone 40 mg).

— IVIG 1 g/kg/day × 2 days.

— Platelet transfusions — usually 2–3× standard dose, often as continuous infusion; despite rapid clearance, transfusions can blunt active bleeding and are appropriate here (not in stable ITP).

— Antifibrinolytics: tranexamic acid 1 g IV q6–8h or aminocaproic acid — useful for mucosal bleeding, menorrhagia (avoid in upper urinary tract bleeding).

— Source control: endoscopy for GI bleed, IR embolization, surgical control as needed.

— Consider emergency splenectomy or vincristine if refractory.

— Consider rFVIIa as last resort (off-label, thrombotic risk).

— STAT non-contrast CT head; neurosurgery consult.

— BP control (SBP <140 if hemorrhagic stroke).

— Elevate head of bed 30°; antiepileptic if seizure.

— Combined IVIG + steroids + platelets + TXA + consider emergent splenectomy.

CCS pearl: In a CCS case for ITP with melena and platelets of 4 — orders to place simultaneously: 2 large-bore IVs, type and cross, methylprednisolone IV, IVIG, platelet transfusion, tranexamic acid, PPI infusion, GI consult, ICU admit. Move the clock in small intervals and re-check CBC q4–6h.

Board pearl: Routine platelet transfusion in stable ITP is not indicated — transfused platelets are destroyed within hours. Reserve for active major bleeding or procedural need.

Severe bleeding in ITP (intracranial, GI, intraocular, severe GU, or any bleeding with hemodynamic instability) is a medical emergency — combine therapies, don't sequence them.

Bundle for life-threatening ITP bleeding:

Reverse contributing factors: hold antiplatelets/anticoagulants, correct uremia (DDAVP, dialysis), correct hypothermia/acidosis, treat coexistent vWD or platelet dysfunction.

Hemoglobin support: transfuse RBCs to keep Hgb appropriate to bleeding context (≥7 baseline, higher with active bleed or coronary disease).

Intracranial hemorrhage specific actions:

For elective procedures, raise to target threshold beforehand with IVIG ± TPO-RA (started 10–14 days pre-op).

Special Populations — Elderly and Renal/Hepatic Impairment

— Higher baseline risk of bleeding (cerebral amyloid, polypharmacy, falls) and higher mortality from ITP-related ICH.

— Treatment threshold may be higher — consider treating at platelets <30 even when asymptomatic; some experts treat at <50 if anticoagulation is required (e.g., AFib).

— Steroid toxicity is amplified: hyperglycemia, osteoporotic fracture, delirium, infection, hypertension, cataracts. Favor short-course dexamethasone over prolonged prednisone.

— Watch for MDS masquerading as ITP — low threshold for bone marrow in elderly with refractory disease or evolving cytopenias.

— Splenectomy carries higher perioperative risk; TPO-RAs are often preferred as second-line — but increased thrombosis risk in this group.

— ITP itself does not require dose adjustment for steroids or IVIG, but IVIG carries AKI risk — use sucrose-free preparations, lower infusion rates, ensure hydration.

— Fostamatinib can raise BP and rarely cause renal effects.

— Eltrombopag — no major renal adjustment but monitor.

— Avoid NSAIDs for symptom control; use acetaminophen.

— Distinguish ITP from cirrhosis-related thrombocytopenia (splenic sequestration, decreased hepatic TPO production) — exam, imaging, LFTs.

— Eltrombopag is hepatotoxic — monitor LFTs q2 weeks initially; avoid or dose-reduce in moderate–severe hepatic impairment.

— Avatrombopag is approved for chronic liver disease–related thrombocytopenia pre-procedure (often confused on exams — that's a different indication, not ITP).

— IVIG generally safe; rituximab may reactivate HBV — screen HBsAg and anti-HBc, prophylactic entecavir if positive.

Key distinction: A cirrhotic with platelets 45 and varices is not ITP — it's hypersplenism/decreased TPO. Treat with avatrombopag/lusutrombopag pre-procedure, not chronic immunosuppression.

Step 3 management: 78-year-old with new petechiae, platelets 18, on apixaban for AFib — hold apixaban, admit, start dexamethasone + IVIG, target platelets ≥50 before resuming anticoagulation, then individualize stroke vs bleeding risk.

Elderly adults (>60–70):

Renal impairment:

Hepatic impairment:

Drug interactions in polypharmacy: eltrombopag chelates with cations (calcium, antacids, iron, dairy) — separate by 2–4 hours.

Special Populations — Pregnancy and Reproductive Considerations

— Gestational: mild (usually >70, rarely <50), late 2nd/3rd trimester, no prior history, resolves postpartum, no neonatal effects. No treatment needed.

— ITP: can occur any trimester, often prior history or platelets <70 in 1st/early 2nd trimester, may require treatment, and antibodies cross placenta → ~10% neonatal thrombocytopenia, <1% severe neonatal bleeding.

— Treat if symptomatic, platelets <30, or as delivery approaches.

— For delivery: ≥50 for vaginal or cesarean; ≥70–80 for neuraxial anesthesia.

— Prednisone (lowest effective dose; watch GDM, hypertension, preterm rupture).

— IVIG for rapid response; first choice in 1st trimester or steroid intolerance.

— Avoid: rituximab (B-cell depletion in neonate), TPO-RAs (limited data, generally avoided though emerging use late in pregnancy in refractory cases), MMF, danazol, cyclophosphamide.

— Splenectomy only if refractory bleeding; ideally 2nd trimester.

— Mode of delivery dictated by obstetric indications, not platelet count.

— Avoid fetal scalp electrodes, vacuum, mid-forceps (neonatal bleeding risk).

— Obtain neonatal cord blood platelet count at delivery; nadir typically days 2–5 postpartum — repeat over the first week.

— Neonates with platelets <30 or bleeding: IVIG ± steroids.

Board pearl: Maternal platelet count does NOT predict neonatal platelet count — even splenectomized mothers with normal counts can have severely thrombocytopenic neonates. Best predictor is prior sibling with neonatal ITP.

Step 3 management: Pregnant patient with known ITP, 36 weeks, platelets 42 — start prednisone or IVIG to reach ≥70 before planned induction, anesthesia/OB/heme coordination, neonatology on standby.

ITP complicates ~1–2 per 1000 pregnancies; distinguish from gestational thrombocytopenia (the most common cause).

Gestational thrombocytopenia vs ITP:

Other pregnancy thrombocytopenias to exclude: preeclampsia, HELLP, AFLP, TTP, APS, DIC, vWD type 2B.

Treatment thresholds in pregnancy:

Preferred therapies:

Delivery planning:

Postpartum: ITP often flares; resume usual therapy. Breastfeeding compatible with prednisone, IVIG; avoid rituximab while breastfeeding per most guidance.

Complications and Adverse Outcomes

— Intracranial hemorrhage: ~0.5%/year in chronic ITP; ~1.5% lifetime; higher in elderly, with platelets <10, on antithrombotics, or with prior bleed/AVM.

— GI bleeding, severe menorrhagia → iron deficiency anemia.

— Hematuria, retinal hemorrhage, soft tissue hematomas.

— Fatigue — underrecognized, often disproportionate to count, affects quality of life.

— Thrombosis paradox: chronic ITP patients have a 2–3× increased risk of arterial and venous thrombosis (mechanism: antiphospholipid antibodies, microparticles, age, splenectomy). Don't assume low platelets means no clots.

— Corticosteroids: hyperglycemia/new-onset diabetes, osteoporosis, hypertension, weight gain, mood changes, psychosis, cataracts, AVN of hip, infection (PJP if prolonged — consider TMP-SMX prophylaxis at >20 mg/d for >4 weeks).

— IVIG: headache (aseptic meningitis), AKI, volume overload, thrombosis, anaphylaxis (especially IgA-deficient patients — screen IgA before first dose if known autoimmune history).

— Anti-D: intravascular hemolysis — rare but can be fatal; black box warning; pre-medicate and monitor hemoglobin/hemoglobinuria for 8 hours; contraindicated in DAT-positive, splenectomized, or Rh-negative patients.

— Rituximab: infusion reactions, infection, HBV reactivation, PML (rare), hypogammaglobulinemia, blunted vaccine response.

— TPO-RAs: thrombosis, rebound thrombocytopenia after stop, marrow fibrosis, hepatotoxicity (eltrombopag).

— Splenectomy: overwhelming post-splenectomy infection (OPSI) — encapsulated organisms (pneumococcus, meningococcus, Hib); lifelong vaccination, antibiotic stewardship, fever action plan; venous thrombosis (portal vein, DVT/PE).

— Fostamatinib: hypertension, diarrhea, hepatotoxicity, neutropenia.

CCS pearl: Any ITP patient post-splenectomy with fever ≥38.3°C: draw cultures, give empiric ceftriaxone immediately (don't wait for cultures), admit if any sepsis sign.

Board pearl: Splenectomized ITP patients carry a "medical alert" status for life — counsel on travel vaccinations (meningococcal boosters, malaria chemoprophylaxis), pet bites (capnocytophaga prophylaxis with amox-clav).

Disease-related complications:

Treatment-related complications:

When to Escalate Care — ICU, Consult, and Admission Decisions

— Platelets ≥20–30 and no/minimal bleeding.

— Reliable follow-up within 3–7 days.

— Adequate social support and access to emergency care.

— Patient education delivered (precautions, warning signs).

— Platelets <20 with mucosal/wet purpura or any active bleeding.

— Platelets <10 even if asymptomatic (variable threshold; high-risk patients).

— Any significant bleeding (GI, GU, intracranial suspicion).

— Need for IVIG/IV steroids and monitoring.

— Comorbidities raising bleed risk: anticoagulation, recent surgery, advanced age, falls.

— Diagnostic uncertainty (rule out TTP, leukemia, DIC).

— Poor outpatient access or unreliable follow-up.

— Suspected or confirmed intracranial hemorrhage.

— Hemodynamically significant GI/GU bleeding.

— Need for continuous platelet infusions, vasopressors, airway protection.

— Severe IVIG reaction, aspiration risk, altered mental status.

— Hematology — for any new ITP requiring treatment, refractory cases, pregnancy.

— Neurosurgery — suspected ICH.

— GI — for GI bleeding source control once platelets adequate.

— OB — pregnancy.

— Surgery — if splenectomy contemplated.

— Infectious disease — pre-splenectomy vaccination planning, post-splenectomy fevers, HBV/HCV/HIV management.

— Rheumatology — secondary ITP from SLE/APS.

— Bleeding controlled, no transfusion in past 24 h.

— Rising platelet trajectory.

— Plan for outpatient steroid taper, follow-up labs in 3–7 days, heme appointment within 1–2 weeks.

— Clear instructions: avoid NSAIDs, contact sports, intramuscular injections; return for bleeding, headache, neurologic change, fever.

Step 3 management: A patient with platelets 8 and only skin petechiae who lives alone and 90 miles from a hospital — admit even though they're asymptomatic. Disposition is a function of bleeding risk, not bleeding alone.

CCS pearl: On CCS, always schedule the heme outpatient follow-up before clicking "end case" — Step 3 reliably rewards transition-of-care orders.

Outpatient management is appropriate for most newly diagnosed adults with:

Admit when:

ICU criteria:

Consults:

Discharge readiness:

Key Differentials — Other Causes of Isolated Thrombocytopenia

— Common culprits: heparin (HIT), quinine/quinidine, vancomycin, linezolid, TMP-SMX, rifampin, valproate, carbamazepine, phenytoin, GPIIb/IIIa inhibitors, checkpoint inhibitors.

— Onset typically 1–2 weeks after drug initiation (or hours with re-exposure).

— Resolves days–weeks after stopping the drug.

— HIT: 4Ts score, typically platelet drop 30–50% (not severe), 5–10 days post-heparin, with thrombosis (not bleeding) — STOP heparin, start non-heparin anticoagulant (argatroban, bivalirudin, fondaparinux), confirm with PF4 ELISA + serotonin release.

— HIV, HCV — must screen in all new ITP.

— Acute viral infections (EBV, CMV, dengue, parvovirus, COVID-19).

— Sepsis (often with DIC).

— H. pylori (eradication can resolve thrombocytopenia in some patients).

— Aplastic anemia (usually pancytopenia).

— MDS, acute leukemia, lymphoma, myelofibrosis, metastatic carcinoma.

— Chemotherapy/radiation effects.

— B12/folate deficiency (often macrocytic anemia + low platelets + hypersegmented neutrophils).

— MYH9-related (Epstein, Fechtner, Sebastian, May-Hegglin) — large platelets, Döhle-like inclusions, sensorineural deafness, nephritis, cataracts.

— Bernard–Soulier — giant platelets, abnormal ristocetin.

— Wiskott–Aldrich — small platelets, eczema, immunodeficiency (X-linked).

— MPL/ANKRD26/RUNX1 — predispose to leukemia.

Key distinction: Drug-induced thrombocytopenia mimics ITP. Always reconstruct a timeline of every new medication, herb, and quinine-containing tonic/cocktail within the past 1–4 weeks before labeling as ITP.

Board pearl: A teenager with mild thrombocytopenia, normal smear, and a father with "low platelets" — think inherited disorder, not ITP. Steroids won't work; you may harm them.

Pseudothrombocytopenia: EDTA-induced platelet clumping. Confirm with smear (clumps visible) and repeat CBC in citrate or heparin tube. No treatment needed.

Drug-induced thrombocytopenia (DITP):

Infection-related:

Bone marrow failure / infiltration:

Inherited thrombocytopenias — lifelong history, family history, syndromic features:

Differentials — Multilineage and Systemic Disease Mimics

— TTP: pentad (thrombocytopenia, MAHA with schistocytes, neuro, renal, fever) — usually only 2–3 features present. ADAMTS13 <10%. Initiate plasma exchange + steroids + caplacizumab emergently; do not transfuse platelets unless life-threatening bleeding.

— HUS / atypical HUS: Shiga-toxin (STEC) or complement-mediated; AKI dominant; eculizumab for aHUS.

— Drug-induced TMA (quinine, calcineurin inhibitors, gemcitabine, VEGF inhibitors).

Key distinction: Schistocytes change everything. Their presence shifts diagnosis from ITP to TMA, and from "give platelets and immunosuppression" to "plasma exchange, withhold platelets, call hematology emergently."

CCS pearl: Any pregnant patient with thrombocytopenia + hypertension + RUQ pain + transaminitis → think HELLP, deliver, don't pursue ITP workup until postpartum.

When thrombocytopenia is not isolated, the differential broadens substantially and often urgently:

Thrombotic microangiopathies (TMAs):

DIC: thrombocytopenia + prolonged PT/aPTT + low fibrinogen + high D-dimer. Treat underlying cause (sepsis, malignancy, OB catastrophe, trauma); supportive transfusions.

HELLP syndrome: pregnancy >20 weeks; hemolysis, elevated LFTs, low platelets — deliver.

Liver disease / cirrhosis: hypersplenism + reduced hepatic TPO; thrombocytopenia + splenomegaly + abnormal LFTs.

Hypersplenism of any cause (portal hypertension, Gaucher, lymphoma) — usually mild–moderate, with splenomegaly.

Systemic lupus erythematosus, antiphospholipid syndrome: can present as isolated thrombocytopenia or as Evans (AIHA + ITP). Check ANA, dsDNA, complements, antiphospholipid panel.

CLL / lymphoma / MGUS: chronic ITP-like picture; flow cytometry, SPEP.

Common variable immunodeficiency (CVID): recurrent infections + autoimmune cytopenias + low immunoglobulins.

Vaccine-induced immune thrombotic thrombocytopenia (VITT): rare, post adenoviral vector COVID vaccines; thrombosis + thrombocytopenia + anti-PF4; treat like autoimmune HIT (non-heparin anticoagulant, IVIG, steroids).

Type 2B von Willebrand disease: gain-of-function vWF binds platelets → consumption thrombocytopenia + bleeding; vWF studies abnormal.

Evans syndrome: combined ITP + autoimmune hemolytic anemia, ± neutropenia; positive DAT, indirect hyperbilirubinemia, low haptoglobin.

Long-Term Plan, Discharge Medications, and Secondary Prevention

— Steroid plan: dexamethasone 40 mg PO daily × 4 days (single course) or prednisone 1 mg/kg/day × 1–2 weeks with structured taper over 4–8 weeks; explicit stop date documented.

— PPI while on steroids if other GI risk factors.

— Calcium + vitamin D, bone density screening if prolonged steroids (>3 months at >7.5 mg/day prednisone).

— Hyperglycemia surveillance: home glucose checks, especially if diabetic or prediabetic.

— PJP prophylaxis (TMP-SMX) for prolonged high-dose steroids or combination immunosuppression.

— Avoid antiplatelets and NSAIDs; use acetaminophen for pain.

— Hold anticoagulation until count safe; individualize restart (heme + cards/neurology).

— Iron supplementation for menorrhagia-related deficiency.

— MedicAlert bracelet (especially post-splenectomy).

— All ITP patients: annual influenza (inactivated), COVID-19 boosters, age-appropriate pneumococcal and shingles vaccines.

— Pre-splenectomy (≥2 weeks before): pneumococcal (PCV15 or 20 followed by PPSV23), meningococcal (ACWY + B), Hib.

— Pre-rituximab: complete vaccinations at least 4 weeks prior — B-cell depletion blunts response for 6–12 months.

— Avoid live vaccines during active immunosuppression.

— Avoid contact sports while platelets <50; helmets for cycling.

— Soft toothbrush, electric razors, fall-proof home.

— Travel: carry medication list and physician letter; avoid live-vaccine destinations during immunosuppression.

Step 3 management: A 45-year-old with chronic ITP on eltrombopag with stable platelets 80 going on a Caribbean cruise — complete HBV/HAV/typhoid vaccines, carry travel letter, ensure 2-week medication buffer, brief on emergency contact in destination country.

Board pearl: Document goals of therapy as "prevent bleeding and maintain QOL," not "normalize platelet count." Many chronic ITP patients live well with counts of 30–50.

Discharge planning checklist for newly diagnosed ITP:

Vaccination strategy:

Lifestyle / activity counseling:

Secondary cause re-screening: annual reassessment for emerging HIV, HCV, SLE, lymphoma — particularly at every relapse.

Fertility, pregnancy planning, contraception: discuss before rituximab/cyclophosphamide; non-estrogen contraceptives if thrombosis risk.

Follow-Up, Monitoring, and Counseling Cadence

— CBC at 3–7 days after starting therapy to confirm response.

— Weekly CBC for the first month, then every 2–4 weeks during taper.

— Hematology consultation within 1–2 weeks of diagnosis.

— Once platelets stable on no therapy: CBC every 1–3 months for the first year, then every 3–6 months.

— Monitor BP, glucose, weight, mood, sleep, infection symptoms at each visit.

— DEXA scan at baseline if anticipated long course; vitamin D level.

— Ophthalmologic exam yearly for prolonged use (cataracts, glaucoma).

— Weekly CBC during titration, then monthly.

— LFTs every 2 weeks initially for eltrombopag, then monthly.

— Watch for thrombosis symptoms; counsel on DVT/PE/stroke signs.

— Avoid abrupt discontinuation — rebound thrombocytopenia; taper over weeks.

— Lifelong fever action plan: any T ≥38.3°C → seek care immediately; carry standby antibiotics (amoxicillin-clavulanate) for travel.

— Vaccine boosters: pneumococcal every 5 years (PPSV23 reboost), meningococcal every 3–5 years, annual influenza.

— Watch for portal/splanchnic vein thrombosis in early postop period.

— Understand chronic relapsing nature; ITP is not curable but is manageable.

— Recognize warning signs: new headache, vision change, bloody stools/urine, heavy menses, prolonged bleeding from minor cuts.

— Pregnancy planning — counsel about maternal–fetal risk; consult heme + MFM preconception.

— Mental health: chronic disease, steroid mood effects, fatigue — screen depression/anxiety; offer support resources (PDSA — Platelet Disorder Support Association).

— Shared decision-making: between TPO-RA, rituximab, splenectomy — discuss durability, side effects, lifestyle.

CCS pearl: A Step 3 outpatient CCS case ends well when you schedule return visit, repeat CBC, and patient education — three explicit actions before signing out.

Board pearl: Treatment success is defined as platelets ≥30 AND at least doubled from baseline AND no bleeding — not normalization. Communicate this expectation up front.

Newly diagnosed adult outpatient ITP:

On steroids:

On TPO-RAs:

Post-rituximab: monitor Ig levels and infection risk for 6–12 months; revaccination plan after B-cell recovery.

Post-splenectomy:

Patient counseling pillars:

Ethical, Legal, and Patient Safety Considerations

— Discuss risks of IVIG (AKI, thrombosis, aseptic meningitis, transfusion reaction), anti-D (intravascular hemolysis, rare deaths), rituximab (PML, HBV reactivation, infection), steroids (psychiatric effects, AVN, infection), splenectomy (irreversible, OPSI).

— Jehovah's Witnesses: plan ahead — IVIG and immunoglobulins are typically refused, as are platelet transfusions; emphasize TPO-RAs, steroids, rituximab, antifibrinolytics, and source control. Document advance directive and acceptable interventions clearly in chart.

— Joint decision-making between mother, OB, heme, and neonatology. Document discussion of treatment options and neonatal thrombocytopenia risk.

— Avoid teratogens (MMF, cyclophosphamide); plan contraception when starting these.

— Communicate active steroid taper, current platelet trajectory, scheduled follow-up, and emergency action plan at every handoff.

— Medication reconciliation at discharge: stop offending agents (quinine, heparin if HIT), restart anticoagulation only after platelets safe.

— Avoid prescription error: "dexamethasone 40 mg daily × 4 days" must be written with explicit stop date — chronic prescribing of high-dose dex is a sentinel event.

— Report transfusion reactions to blood bank and FDA MedWatch.

— Disclose medical errors (over-anticoagulation, missed splenectomy vaccination) per institutional policy and shared with patient (ethical duty of honesty).

Step 3 management: A Jehovah's Witness with severe ITP bleeding refuses platelet transfusion. Respect the directive, intensify alternatives — IV methylprednisolone, IVIG (clarify acceptance — many accept), TPO-RA, tranexamic acid, rFVIIa as salvage, urgent splenectomy if needed. Document conversation, witnesses, capacity assessment.

Board pearl: A "never event" in ITP care is failure to vaccinate before splenectomy. Build a pre-op checklist.

Informed consent for blood products and immunosuppression:

Pregnancy:

Transition-of-care safety (high-yield Step 3):

Mandatory reporting and disclosure:

Driving and occupational safety: counsel patients on driving restrictions during severe thrombocytopenia or steroid-induced psychosis; document discussion.

Vaccination requirements: ensure pre-splenectomy vaccines are given ≥2 weeks before surgery — failure to vaccinate before elective splenectomy is a documented safety gap.

End-of-life and goals of care: in refractory ITP with multiorgan comorbidity, discuss goals — chronic ITP rarely kills directly, but treatment burden and hemorrhage can dominate quality of life.

High-Yield Associations and Rapid-Fire Facts

Board pearl: If the stem mentions giant platelets + sensorineural deafness or nephritis, think MYH9 disorder, not ITP.

Key distinction: Bleeding without thrombocytopenia in a patient with prior ITP — consider acquired platelet dysfunction (drug, uremia, vWD) before assuming ITP relapse.

ITP = isolated thrombocytopenia + normal smear + exclusion of other causes. No confirmatory test.

First-line: dexamethasone 40 mg × 4 days OR prednisone 1 mg/kg.

Rapid response needed: add IVIG 1 g/kg (or anti-D if Rh+, non-splenectomized).

TPO-RAs: romiplostim (SC), eltrombopag (PO, watch LFTs and cation chelation), avatrombopag (PO, no food/LFT restrictions).

Rituximab: screen HBV first; vaccinate before.

Splenectomy: defer ≥12 months; vaccinate ≥2 weeks pre-op; risk of OPSI lifelong.

Fostamatinib: Syk inhibitor; refractory ITP.

Treatment threshold: platelets <30 or any bleeding.

Procedure thresholds: dental 30, minor surgery 50, major 80, neurosurgery 100, neuraxial 70–80.

Pregnancy: prednisone or IVIG preferred; avoid rituximab; mode of delivery is obstetric, not platelet-driven; neonatal counts checked at delivery and over first week.

Don't transfuse platelets in stable ITP — only for life-threatening bleeding or procedural need.

Don't give anti-D to Rh-negative, DAT+, or splenectomized patients.

ITP thrombosis paradox: increased VTE and arterial risk despite low counts, especially after splenectomy and on TPO-RAs.

H. pylori eradication can resolve ITP in some patients.

Always screen HIV and HCV in new adult ITP.

Refractory ITP → revisit diagnosis (MDS, CLL, APS, inherited disorder).

Children with ITP: observe most — usually self-limited; adults: usually treat and chronic.

Evans syndrome: ITP + AIHA (positive DAT).

HIT vs ITP: HIT = mild thrombocytopenia + thrombosis 5–10 days post-heparin → stop heparin, start argatroban/bivalirudin/fondaparinux.

TTP vs ITP: TTP has schistocytes, neuro, renal, fever, ADAMTS13 <10% → plasma exchange + steroids + caplacizumab, NOT platelet transfusion.

VITT: post-adenoviral vaccine; thrombosis + thrombocytopenia + anti-PF4 → IVIG + non-heparin anticoagulant.

Type 2B vWD looks like ITP — abnormal vWF studies, family history.

Board Question Stem Patterns

— 32-year-old woman with 1 week of leg petechiae, gum bleeding, menorrhagia. Platelets 14, Hgb 12, WBC 7, smear normal. HIV/HCV negative.

— Answer: Dexamethasone 40 mg PO daily × 4 days (or prednisone). IVIG if bleeding active.

— 45-year-old woman with confusion, fever, AKI, platelets 18, Hgb 7 with schistocytes.

— Answer: Plasma exchange + steroids ± caplacizumab; do NOT give platelets unless life-threatening hemorrhage. Send ADAMTS13.

— Post-op CABG patient on heparin × 7 days, platelets drop from 220 to 110, new DVT.

— Answer: Stop all heparin, start argatroban or bivalirudin, 4Ts and PF4 antibody.

— 28 weeks gestation, no history, platelets 95, asymptomatic — gestational thrombocytopenia, observe.

— vs. 8 weeks gestation, platelets 22 with bruising — ITP, treat with prednisone or IVIG.

— Year-long history despite steroids and IVIG; recurrent symptomatic counts <20.

— Answer: TPO-RA or rituximab (defer splenectomy ≥12 months from diagnosis).

— ITP patient needs colonoscopy with biopsy, platelets 28.

— Answer: Increase to ≥50 with IVIG ± steroids before procedure.

— Started TMP-SMX 10 days ago, now platelets 12 with petechiae.

— Answer: Stop drug, supportive care; may not need immunosuppression.

— Patient post-splenectomy 2 years ago with fever 39.0 and chills.

— Answer: Empiric ceftriaxone immediately, cultures, admit.

— Lifelong mild thrombocytopenia, family history, giant platelets, sensorineural hearing loss.

— Answer: MYH9 disorder, not ITP.

— Thrombocytopenia + anemia + positive DAT + indirect hyperbilirubinemia.

— Answer: Evans syndrome; steroids + IVIG; consider rituximab.

Step 3 management: When stems mention only mild bruising and platelets 60 in an otherwise well adult — the answer is often observation with hematology follow-up, not immediate treatment.

Board pearl: If the stem mentions splenomegaly, the answer is almost never primary ITP — look for another diagnosis (cirrhosis, CLL, lymphoma).

Pattern 1 — Classic adult ITP:

Pattern 2 — TTP mimic:

Pattern 3 — HIT:

Pattern 4 — Pregnancy-related:

Pattern 5 — Refractory ITP:

Pattern 6 — Pre-procedure prep:

Pattern 7 — Drug-induced:

Pattern 8 — Post-splenectomy fever:

Pattern 9 — Inherited disorder:

Pattern 10 — Evans syndrome:

One-Line Recap

High-yield recap bullets:

Board pearl: ITP's defining Step 3 truth — manage by bleeding risk and trajectory, not by chasing a normal platelet number.

Adult ITP is a clinical diagnosis of isolated thrombocytopenia from immune-mediated platelet destruction and impaired production, treated based on bleeding and count thresholds — corticosteroids (± IVIG for rapid rise) first, with TPO-RAs, rituximab, fostamatinib, or splenectomy as second-line, and with vigilance for secondary causes, treatment toxicity, and the paradoxical thrombosis risk that defines this disease.

Diagnose by exclusion: isolated thrombocytopenia + normal smear + HIV/HCV negative + no drug trigger + no atypical features. No confirmatory test required; bone marrow only for atypical or refractory cases.

Treat when platelets <30 or any clinically significant bleeding. First-line: dexamethasone 40 mg × 4 days or prednisone 1 mg/kg; add IVIG 1 g/kg when rapid response is needed (active bleed, surgery, pregnancy). Do NOT transfuse platelets in stable ITP — only in life-threatening hemorrhage or for procedures.

Second-line (after 12 months ideally): TPO-RAs (romiplostim, eltrombopag, avatrombopag), rituximab (HBV screen!), fostamatinib, or splenectomy (vaccinate ≥2 weeks pre-op, lifelong OPSI risk). Match therapy to comorbidities, pregnancy plans, and preferences.

Never miss the mimics: TTP (schistocytes — plasma exchange, not platelets), HIT (thrombosis on heparin — stop heparin, argatroban), DIC, drug-induced, gestational thrombocytopenia, inherited thrombocytopenias, MDS/leukemia, hypersplenism. Pregnancy: prednisone/IVIG, target ≥50 vaginal / ≥80 neuraxial, mode of delivery is obstetric, screen neonatal platelets postpartum. Always counsel on bleeding precautions, avoid NSAIDs/contact sports, MedicAlert post-splenectomy, vaccinate appropriately, follow up with hematology, and document a transition-of-care plan — Step 3 rewards every one of these touchpoints.