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Petechiae: Pinpoint Hemorrhages — Causes, Evaluation, and Red Flags

Petechiae are 1–2 mm, non-blanching, red-purple macules resulting from capillary hemorrhage. Unlike bruises, they don't change color with pressure. They signal platelet, vascular, or coagulation pathology.

Mechanism-Based Classification

MechanismCausesExamples
Thrombocytopenia (↓ platelets) Decreased production, increased destruction, sequestration ITP, TTP, HUS, DIC, leukemia, chemotherapy, alcohol, viral (HIV, HCV, EBV), drugs (heparin/HIT, sulfa, quinine)
Platelet dysfunction Qualitative defects Uremia, von Willebrand disease, aspirin/NSAIDs, antiplatelets, myeloproliferative neoplasms
Vascular fragility Defective collagen/connective tissue Scurvy (vit C), Ehlers-Danlos, Cushing's, steroid use, amyloidosis, Henoch-Schönlein purpura (IgA vasculitis)
Coagulopathy Factor deficiency/inhibition Liver disease, DIC, warfarin, factor deficiencies
Mechanical / Trauma Increased venous pressure, physical force Vomiting, coughing, Valsalva (face/neck), tourniquet, CPR, childbirth, strangulation
Infection / Sepsis Endothelial injury, DIC, toxins Meningococcemia, Rocky Mountain spotted fever, endocarditis, viral hemorrhagic fevers

Clinical Assessment

  1. Distribution: Dependent areas (legs) vs. truncal (more ominous); mucosal involvement.
  2. Associated signs: Ecchymoses, hemarthrosis, hematuria, melena, neurologic deficits.
  3. Vitals: Fever, hypotension (sepsis), hypertension (pre-eclampsia).
  4. Labs: CBC (platelets!), PT/INR, aPTT, fibrinogen, D-dimer, creatinine, LFTs, blood culture if febrile.
  5. Peripheral smear: Schistocytes (TTP/HUS/DIC), blasts (leukemia).

Red Flags: Emergency Evaluation

  • Platelets <20k or rapidly falling
  • Fever + petechiae (meningococcemia, sepsis)
  • Neurologic changes (TTP, intracranial hemorrhage)
  • Active bleeding (mucosal, GI, GU)
  • Purpura fulminans (rapidly progressing hemorrhagic necrosis)
  • New-onset in immunocompromised or on anticoagulants

Common Benign Causes

  • Post-vomiting/coughing facial petechiae (resolves in days)
  • Tourniquet/BP cuff petechiae (distal to site)
  • Strenuous exercise (weightlifting — Valsalva)
  • Minor trauma in elderly (senile purpura, actinic damage)

Any unexplained petechiae warrant same-day CBC and clinical assessment.

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