Thrombocytopenia

Platelet count <150,000/mm³ — determine if decreased production, increased destruction, or sequestration; etiology drives management

Symptoms / Associated Sx

  • Petechiae (pinpoint non-blanching skin hemorrhages), purpura, ecchymoses

  • Mucosal bleeding: gingival bleeding, epistaxis, menorrhagia

  • GI bleeding, hematuria (severe thrombocytopenia)

  • CNS bleeding (intracranial hemorrhage — severe, <10,000)

  • May be asymptomatic if mild (>50,000)

Denies

  • Recent new medication (reduces drug-induced thrombocytopenia if absent — always review full medication list)

  • Fever + hemolytic anemia + renal failure (rules out TTP/HUS if absent — devastating if missed)

  • Recent heparin exposure (rules out HIT if absent)

  • Liver disease or portal hypertension (rules out splenic sequestration as primary)

Social History (SHx)

Medications (all, including OTCs, herbals — drug-induced thrombocytopenia), alcohol use (direct marrow suppression + liver disease + hypersplenism), prior thrombocytopenia episodes, recent infections (viral — EBV, CMV, HIV, HCV), pregnancy (gestational thrombocytopenia vs. HELLP), family history of bleeding disorders.

Main Etiology

  • Decreased production: Bone marrow suppression (chemotherapy, radiation, medications), aplastic anemia, marrow infiltration (leukemia, myeloma, myelofibrosis), B12/folate deficiency, alcohol

  • Increased destruction (immune): ITP (immune thrombocytopenic purpura), drug-induced (quinine, heparin, vancomycin, piperacillin, trimethoprim-sulfamethoxazole, many others), viral (HIV, HCV, EBV), antiphospholipid syndrome, lupus

  • Increased consumption (non-immune): DIC, TTP/HUS, HELLP syndrome, sepsis

  • Sequestration: Hypersplenism from portal hypertension (cirrhosis, liver disease)

  • Dilutional: Massive transfusion, aggressive fluid resuscitation

Most Common DDx

  • Drug-induced thrombocytopenia (new medication within days-weeks; platelet recovery after stopping offending agent; common culprits: heparin, quinine, vancomycin, trimethoprim-sulfamethoxazole, piperacillin-tazobactam — review all medications)

  • Sepsis-related thrombocytopenia (ICU patient + infection + falling platelets; DIC labs variable; treat underlying infection → platelets recover)

  • ITP (isolated thrombocytopenia; no other cytopenias; no DIC; no schistocytes; diagnosis of exclusion; responds to steroids)

  • HIT (heparin exposure + platelet fall >50% + new thrombosis; 4Ts score; stop heparin → argatroban — see HIT section)

  • TTP (microangiopathic hemolytic anemia + thrombocytopenia + neurologic symptoms ± fever ± renal failure; schistocytes on smear; ADAMTS13 <10% confirms; plasma exchange is treatment — see TMA section)

  • Liver disease / hypersplenism (mild-moderate thrombocytopenia; splenomegaly; cirrhosis; elevated LFTs; SAAG ≥1.1 if ascites — platelet count rarely <50k from hypersplenism alone)

  • Gestational thrombocytopenia (mild, asymptomatic; last trimester; platelet >70k; no treatment; resolves post-partum — vs. ITP which can be more severe)

DATA

  • CBC with differential (isolated thrombocytopenia vs. pancytopenia; platelet count trend)

  • Peripheral blood smear (schistocytes → TTP/HUS/DIC; giant platelets → ITP; hypersegmented PMNs → B12/folate)

  • Coagulation panel — PT/INR, PTT, fibrinogen, D-dimer (DIC screen)

  • LFTs, albumin (liver disease); BMP (renal failure — HUS)

  • LDH, indirect bilirubin, haptoglobin (hemolysis markers — TTP/HUS)

  • Direct Coombs test (immune hemolytic anemia)

  • HIV, HCV, HBV serology (secondary ITP)

  • ANA, antiphospholipid antibodies (lupus, APS)

  • H. pylori testing (associated with ITP — treat if positive)

  • ADAMTS13 activity level (send before plasma exchange if TTP suspected)

  • 4Ts score if HIT suspected (Thrombocytopenia, Timing, Thrombosis, oTher causes — score ≥4 = intermediate-high probability → send HIT antibody + functional assay)

  • Bone marrow biopsy (if pancytopenia or marrow infiltration suspected)

Home Meds

  • Heparin (any form — unfractionated, LMWH, flushes; stop immediately if HIT suspected)

  • Drug-induced offenders: quinine, vancomycin, trimethoprim-sulfamethoxazole, piperacillin-tazobactam, linezolid, carbamazepine, phenytoin, valproate, rifampin, many others (review all)

  • Antiplatelet agents (hold if platelets <30k or active bleeding)

  • NSAIDs (worsen platelet function)

Plan

  • Stop all potentially offending medications (drug-induced thrombocytopenia — most important initial step)

  • Platelet transfusion thresholds:

    • Prophylactic: platelets <10k (stable); <20k (fever/infection); <50k (planned surgery/procedure); <100k (neurosurgery or epidural)

    • Active bleeding with thrombocytopenia: transfuse to keep platelets ≥50k (or ≥100k for CNS bleed)

    • DO NOT transfuse platelets in TTP or HIT — can worsen thrombosis ("pour fuel on the fire")

  • ITP (immune thrombocytopenic purpura):

    • Mild (platelets 30–80k, asymptomatic) → monitor; no treatment required

    • Moderate-severe (platelets <30k or bleeding): Prednisone 1–2 mg/kg/day PO × 4–6 weeks then taper (first-line)

    • Severe bleeding or very low platelets (<10k + bleeding): IVIG 1 g/kg IV × 1–2 days (rapid response within 24–48h) ± methylprednisolone 1 g IV daily × 3 days + platelet transfusion

    • Refractory ITP: Rituximab 375 mg/m² IV weekly × 4 doses; eltrombopag 50 mg PO daily (TPO receptor agonist); splenectomy (definitive — 60–70% sustained remission)

  • Drug-induced thrombocytopenia: Remove offending agent; IVIG if severe bleeding while drug clears; platelets if critically low (<10k or active hemorrhage)

  • Sepsis-related: Treat infection; support; platelet transfusion if <10k or active bleeding; DIC protocol if concurrent

  • Liver disease / hypersplenism: Treat portal hypertension; platelet transfusion if procedure needed and <50k; avatrombopag or lusutrombopag (TPO agonist) pre-procedure

  • Avoid NSAIDs, aspirin in thrombocytopenia

  • Trend CBC daily; coags if DIC suspected; trend LFTs and renal function

  • Hematology consult for ITP, HIT, TTP, or unexplained thrombocytopenia <50k

  • PT/OT — fall precautions; bleeding precautions

  • Discharge: Prednisone taper schedule (ITP); avoid offending medications; platelet count recheck 1–2 weeks; hematology follow-up; bleeding precautions education; avoid contact sports if platelets <50k

Red Flags

  • Schistocytes + thrombocytopenia + hemolysis → TTP → plasma exchange immediately (do not wait for ADAMTS13)

  • Heparin + thrombocytopenia + new thrombosis → HIT → stop all heparin; start argatroban urgently

  • Platelets <10,000 or active CNS/GI/mucosal bleeding → platelet transfusion + hematology emergently

  • DIC (prolonged PT/PTT + low fibrinogen + elevated D-dimer + thrombocytopenia) → treat underlying cause + FFP + cryoprecipitate + platelets

  • Pancytopenia + thrombocytopenia → aplastic anemia or leukemia → bone marrow biopsy urgently

Senior IM Resident Pearls

  • NEVER transfuse platelets in TTP or HIT — platelet transfusion in TTP causes thrombotic catastrophes (stroke, MI); in HIT worsens thrombosis; this is a classic and dangerous mistake

  • Pseudothrombocytopenia: Platelet clumping in EDTA tube — always confirm with citrate tube or peripheral smear before treating; common in the lab; no bleeding risk

  • ITP in adults is chronic in ~80% vs. acute and self-limited in children — set appropriate long-term treatment expectations

  • H. pylori testing in ITP — eradication achieves platelet response in ~50% of H. pylori-positive ITP patients; low-cost intervention worth testing in all ITP patients

  • 4Ts score for HIT: Thrombocytopenia severity + Timing of fall + Thrombosis + oTher causes — score ≥4 = intermediate/high probability; send HIT antibody (ELISA) AND functional assay (serotonin release assay — gold standard)

  • Common mistake: Not reviewing all medications including OTC and herbals when faced with new thrombocytopenia — drug-induced is common and completely reversible with removal of offending agent

The 10-Second Algorithm

1. Confirm it's real
→ Smear (clumping?)

2. PT/PTT normal or abnormal?

  • Normal → ITP / HIT / TTP / HUS

  • Abnormal → DIC / liver disease

3. Schistocytes?

  • Yes → TTP/HUS/DIC

  • No → continue

4. Isolated or pancytopenia?

  • Isolated → ITP/drug/HIT

  • Pancytopenia → marrow disease

5. Splenomegaly?

  • Yes → sequestration

6. Pregnant?

  • HTN/LFT abnormalities → HELLP

  • Mild isolated thrombocytopenia → gestational

This framework will correctly classify the vast majority of thrombocytopenia consults and admissions on Internal Medicine.

Thrombocytopenia — Fast One-Line Rules (Expanded)

Isolated thrombocytopenia + normal smear + normal PT/PTT
→ ITP, drug-induced thrombocytopenia, HIV/HCV, autoimmune disease

Large platelets on smear + isolated thrombocytopenia
→ ITP (peripheral destruction)

Recent new medication (days–weeks)
→ Drug-induced thrombocytopenia
(Vanc, Linezolid, Bactrim, Pip-Tazo, Heparin, Valproate, Phenytoin, Carbamazepine)

Recent heparin + platelet drop >50% ± thrombosis
→ HIT
(4Ts score → PF4 Ab → SRA confirmation)

Schistocytes + thrombocytopenia + normal PT/PTT
→ TTP/HUS
(LDH ↑, Haptoglobin ↓, Indirect bili ↑)

Schistocytes + thrombocytopenia + PT/PTT prolonged + D-dimer ↑ + fibrinogen ↓
→ DIC

MAHA + thrombocytopenia + neurologic symptoms
→ TTP
(Plasma exchange NOW; don't wait for ADAMTS13)

MAHA + thrombocytopenia + severe AKI
→ HUS

Thrombocytopenia + sepsis + elevated lactate
→ Sepsis-related consumption ± DIC

Pancytopenia
→ Bone marrow failure/infiltration
(Leukemia, MDS, aplastic anemia, myelofibrosis, metastatic cancer)

Blasts on smear
→ Acute leukemia

Teardrop cells + splenomegaly
→ Myelofibrosis / marrow infiltration

Macrocytosis + hypersegmented neutrophils
→ B12/Folate deficiency

Macrocytosis + heavy alcohol use
→ Alcohol-induced marrow suppression

Splenomegaly + cirrhosis + abnormal LFTs
→ Hypersplenism / sequestration

Pregnant + mild thrombocytopenia (>70k)
→ Gestational thrombocytopenia

Pregnant + HTN + elevated LFTs + hemolysis
→ HELLP syndrome

Pregnant + HTN + proteinuria
→ Preeclampsia

Platelet clumping on smear
→ Pseudothrombocytopenia
(repeat CBC in citrate tube)

Senior Resident Rapid Pattern Recognition

PT/PTT Normal

Isolated thrombocytopenia

  • ITP

  • Drug-induced

  • HIT

  • HIV/HCV

  • Early viral infection

Schistocytes present

  • TTP

  • HUS

  • Mechanical valve hemolysis

PT/PTT Abnormal

Low fibrinogen + D-dimer high

  • DIC

Liver disease pattern

  • Cirrhosis

  • Hypersplenism

Other Cell Lines Also Low

Pancytopenia

  • Leukemia

  • MDS

  • Aplastic anemia

  • Marrow infiltration

  • Chemotherapy

  • B12/Folate deficiency

"Don't Miss" Diagnoses

🚨 TTP

  • Schistocytes

  • Hemolysis

  • Neuro symptoms

  • Platelets low

  • PT/PTT normal

🚨 HIT

  • Heparin exposure

  • Platelets fall >50%

  • New clot

🚨 DIC

  • Septic/shock patient

  • PT/PTT prolonged

  • Fibrinogen low

  • D-dimer very high

🚨 Acute leukemia

  • Pancytopenia

  • Blasts

  • Constitutional symptoms

Labs

Admission

  • CBC with diff

  • Peripheral smear (must review personally)

  • CMP

  • BMP

  • PT/INR

  • PTT

  • Fibrinogen

  • D-dimer

  • LDH

  • Haptoglobin

  • Indirect bilirubin

  • Reticulocyte count

Secondary Causes

  • HIV

  • HCV

  • HBV

  • ANA

  • Antiphospholipid antibodies

  • H. pylori testing

If HIT Suspected

  • 4Ts score

  • HIT ELISA

  • Serotonin Release Assay (SRA)

If TTP Suspected

  • ADAMTS13 activity

  • ADAMTS13 inhibitor

Additional

  • Direct Coombs

  • B12

  • Folate

  • Iron studies

  • Ferritin

Trending

  • CBC daily

  • Coags daily if DIC concern

  • LDH/Haptoglobin daily if hemolysis

  • Renal function daily

  • LFTs daily

Imaging

If Splenic Sequestration

RUQ Ultrasound

Evaluate:

  • Cirrhosis

  • Portal HTN

  • Splenomegaly

If Suspected Malignancy

CT Chest/Abdomen/Pelvis

Evaluate:

  • Lymphadenopathy

  • Splenomegaly

  • Malignancy

If CNS Symptoms

CT Head STAT

Evaluate:

  • Intracranial hemorrhage

Procedures

Bone Marrow Biopsy

If:

  • Pancytopenia

  • Abnormal smear

  • Leukemia concern

  • MDS concern

  • Unexplained thrombocytopenia

Plasma Exchange (PLEX)

If:

  • Suspected TTP

DO NOT wait for ADAMTS13.

Medications

ITP

Prednisone

  • 1–2 mg/kg PO daily

Taper over 4–6 weeks

Severe ITP

IVIG

  • 1 g/kg IV daily x1–2 days

Life-Threatening Bleeding

Methylprednisolone

  • 1 g IV daily x3 days

PLUS

IVIG

  • 1 g/kg IV

Refractory ITP

Rituximab

  • 375 mg/m² IV weekly x4

Eltrombopag

  • 50 mg PO daily

HIT

Stop ALL Heparin

Including:

  • LMWH

  • Flushes

  • Heparin drips

Argatroban

  • Continuous IV infusion

OR

Bivalirudin

  • Continuous IV infusion

TTP

Plasma Exchange Daily

PLUS

Methylprednisolone

  • 1 mg/kg/day

Consider:

  • Rituximab

  • Caplacizumab

DIC

Treat underlying cause

May require:

  • FFP

  • Cryoprecipitate

  • Platelets

Platelet Transfusion Thresholds

<10,000

  • Transfuse platelets

<20,000 + Fever/Sepsis

  • Transfuse platelets

<50,000

  • Surgery/procedure

  • Active bleeding

<100,000

  • Neurosurgery

  • Epidural

  • CNS bleed

DO NOT TRANSFUSE PLATELETS

  • TTP

  • HIT

Unless immediately life-threatening bleeding.

Hold

  • Heparin (if HIT concern)

  • Aspirin

  • Clopidogrel

  • NSAIDs

  • Anticoagulation if severe thrombocytopenia

  • Suspected offending medications

Common offenders:

  • Vancomycin

  • TMP-SMX

  • Pip-tazo

  • Linezolid

  • Quinine

  • Valproate

  • Carbamazepine

  • Phenytoin

  • Rifampin

Consults

Hematology (Strongly Recommended)

  • Platelets <50k

  • ITP

  • HIT

  • TTP

  • DIC

  • Unexplained thrombocytopenia

Transfusion Medicine

  • TTP

  • Plasma exchange

Hepatology

  • Cirrhosis

  • Portal hypertension

PT/OT

  • Fall precautions

  • Deconditioning

Nursing

  • Bleeding precautions

  • Fall precautions

  • Avoid IM injections

  • Avoid unnecessary venipuncture

  • Telemetry if severe bleeding

Notify physician:

  • New neurologic symptoms

  • Melena

  • Hematemesis

  • Hematuria

  • Epistaxis

  • Platelets <10k

Follow-Up

  • CBC daily

  • Smear review

  • HIT testing

  • ADAMTS13

  • Hemolysis labs

  • Coags

  • Renal function

  • LFTs

Escalation

TTP

Findings:

  • Thrombocytopenia

  • Hemolysis

  • Schistocytes

→ Plasma exchange immediately
→ ICU

HIT

Findings:

  • Platelet fall >50%

  • New thrombosis

  • Recent heparin

→ Stop all heparin
→ Argatroban

DIC

Findings:

  • Elevated PT/PTT

  • Low fibrinogen

  • Elevated D-dimer

→ ICU
→ Treat underlying cause

Severe Bleeding

  • CNS bleed

  • GI bleed

  • Pulmonary hemorrhage

→ Platelets >50k goal
→ >100k if CNS bleed

Pancytopenia

→ Bone marrow biopsy
→ Leukemia/aplastic anemia workup

Discharge

  • Avoid offending medications

  • Bleeding precautions

  • Hematology follow-up

  • Repeat CBC in 1–2 weeks

  • Steroid taper if ITP

  • Avoid contact sports if platelets <50k