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Spencer Lessans


  • Classified as either mild (100K-150K), moderate (50K-99K), or severe (<50K)
  • Can be divided into different causes
    • Decreased platelet production
      • Decreased TPO: Cirrhosis
      • Bone marrow suppression: sepsis, EtOH, infections (HIV, tick-borne [RMSF, anaplasma, erhlichia], leptospirosis, parvovirus aplastic crisis), certain drugs (vancomycin, linezolid, bactrim, valganciclovir, immunosuppressive therapies, chemotherapies, allopurinol, colchicine)
      • Bone marrow failure
      • Infiltrative: malignancies (leukemia, lymphoma, myeloma, metastatic solid tumors), infections (TB, NTM, fungal infections), fibrosis (myelofibrosis)
      • Aplastic anemia
      • Nutrient deficiencies: Copper (primary or caused by elevated zinc levels), B12, folate
    • Platelet destruction/consumption:
      • Immune thrombocytopenia (ITP):
      • Drug-induced (quinines, sulfonamides, beta-lactams, vancomycin, meropenem, valacyclovir, PPIs, H2 blockers, anti MTB therapy)
      • Heparin-induced thrombocytopenia
      • Infections (HIV, HBV, HCV, CMV, EBV, malaria, H. pylori)
      • Autoimmune disorders (SLE, scleroderma)
      • Thyroid disease
      • Bleeding
      • Idiopathic
      • Thrombotic microangiopathies (TMAs)
      • TTP (acquired, hereditary)
      • HUS
      • DIC (sepsis, APML, pancreatitis, transfusion reaction, HELLP)
      • Drug-induced (Calcineurin inhibitors, gemcitabine, cocaine)
      • Autoimmune (scleroderma renal crisis)
      • Complement-mediated (atypical HUS)
      • Catastrophic antiphospholipid syndrome (APLS)
      • Hypertensive emergency
    • Sequestration: Hypersplenism or splenic sequestration (e.g. cirrhosis)
    • Pseudothrombocytopenia: platelet clumping
    • Dilutional: gestational thrombocytopenia


  • Usually asymptomatic
  • Bleeding due to low platelet counts presents as petechiae
  • Some causes of thrombocytopenia have a paradoxical increased risk of thrombosis (HIT, DIC, TMA, VITT from the AstraZeneca or Johnson & Johnson COVID vaccines)


  • Repeat CBC w/ diff PLUS a peripheral smear
  • Citrated platelet count (to rule out pseudothrombocytopenia though a smear without clumping is sufficient to exclude this) and immature platelet fraction (IPF)
  • IPF can help differentiate between decreased platelet production vs. increased platelet production (in setting of destruction/consumption)
  • Medication reconciliation to look for any offending drugs
  • TMA/DIC labs: Haptoglobin, LDH, LFTs, PT/PTT, fibrinogen, peripheral smear
  • Viral serologies: HIV, HBV, HCV, EBV, CMV, parvovirus (if clinically indicated)
  • Infectious work-up
  • Sepsis: blood cultures
  • Fungal work-up (if clinically indicated): 1,3-Beta-D-Glucan, aspergillus galactomannan, urine blasto Ag, urine and serum histo Ag, crypto Ag
  • Tick-borne (if clinically indicated): RMSF, Ehrlichia, Anaplasma
  • Leptospirosis (if clinically indicated)
  • TB and/or NTM (if clinically indicated): AFB, interferon-Gamma release assay
  • Autoimmune work-up (if clinically indicated): ESR, CRP, ANA w/ reflex, RF
  • Nutritional studies: B12, folate, copper, zinc
  • TSH to screen for thyroid disease
  • Abdominal U/S to look for splenomegaly (or review recent imaging)
  • Bone marrow biopsy (if clinically indicated): co-existing cytopenias raise suspicion for bone marrow involvement (particularly if present prior to admission)
  • HIT work-up: Calculate 4T score: if 4+, order HIT Ab ELISA. If (+), serotonin-release assay (SRA) will reflex for confirmation


  • Platelet transfusion indications
    • CNS or ocular bleeding: <100K
    • Pt actively bleeding or plan for OR: <50K
    • Plan for central line, bronch, LP, diagnostic endoscopy, or bone marrow biopsy: <20K
    • Afebrile, hospitalized pts: <10K
  • HIT management: Stop any heparin product and start argatroban.
  • Schistocytes on smear:
    • Think TTP or DIC when there are schistocytes on smear and thrombocytopenia
    • If DIC is excluded, consult Hematology to discuss sending ADAMTS13 and starting PLEX. A Vascath is needed for PLEX