Purpura

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Background

Normal dermal anatomy.
  • Purpura results from extravasation of blood into the skin or mucous membranes
  • Palpable purpura are a result of either perivascular inflammation (vasculitis) or infection
  • Non-palpable petechiae usually occur in low platelet states such as ITP and DIC
  • Key EM distinction: palpable (vasculitis/infection) vs. non-palpable (thrombocytopenia/coagulopathy)
  • Fever + purpura in a child is meningococcemia until proven otherwise — requires emergent antibiotics

Rash Red Flags[1]

Clinical Features

Both petechiae and purpura do not blanch with pressure (distinguishing feature from erythema)

  • Purpura subdivided by size:
    • <2mm of hemorrhage: petechiae
    • >2mm of hemorrhage: purpura
    • Large areas: ecchymoses
  • Palpable purpura: raised, can be felt; indicates vasculitis or septic emboli
  • Non-palpable (flat) purpura: platelet disorder, coagulopathy, or fragile vessels

Key Physical Exam Features

  • Distribution: dependent areas (gravitational), generalized, or localized
  • Palpability: palpable vs. non-palpable
  • Associated findings: fever, arthralgia, abdominal pain, renal involvement (Henoch-Schönlein purpura / IgA vasculitis)
  • Mucosal involvement: oral petechiae, gingival bleeding (suggests severe thrombocytopenia)
  • Signs of systemic illness: hemodynamic instability, altered mental status

Purpural Rash

Red Flags

  • Fever + petechiae/purpura (meningococcemia, endocarditis, Rocky Mountain spotted fever)
  • Rapidly spreading purpura (DIC, purpura fulminans)
  • Platelets <10,000 (high risk of spontaneous bleeding)
  • Active hemorrhage from mucosal sites
  • Altered mental status with purpura (TTP — emergent plasma exchange)

Differential Diagnosis

Petechiae/Purpura (by cause)

Petechiae/Purpura (by findings)

Evaluation

All Patients

  • CBC with platelet count — most critical initial test
  • Peripheral blood smear (schistocytes in TTP/HUS, blasts in leukemia)
  • PT/INR, PTT (coagulopathy assessment)
  • BMP (renal function — assess for HUS, TTP)

If Thrombocytopenic

  • Consider DIC panel: fibrinogen, D-dimer, fibrin degradation products
  • LDH, haptoglobin, reticulocyte count if concern for TTP/HUS
  • Type and screen
  • Consider blood cultures, lactate if febrile

If Platelets Normal

  • Evaluate for coagulopathy (PT/INR, PTT)
  • If palpable purpura: ESR, CRP, UA (renal involvement), complement levels (C3, C4)
  • Consider skin biopsy referral (vasculitis workup)
  • Blood cultures, lactate if concern for septic emboli or endocarditis

Pediatric

  • For children with fever and petechiae/purpura consider using the Barts Health NHS Trust guideline for workup, which performed well in the Petechiae in Children (PiC) study[2][3]
Fever and non-blanching rash in children algorithm from Barts Health NHS Trust guideline.

Management

Emergent

  • Meningococcemia: immediate IV ceftriaxone (do not delay for LP); fluid resuscitation
  • DIC: treat underlying cause; transfuse platelets, FFP, cryoprecipitate as needed
  • TTP: emergent hematology consultation for plasma exchange; do NOT transfuse platelets (can worsen)
  • Severe thrombocytopenia (<10,000) with active bleeding: platelet transfusion

Condition-Specific

  • ITP: if bleeding or platelets <30,000: IV dexamethasone, consider IVIG; hematology consultation
  • Henoch-Schönlein purpura / IgA vasculitis: supportive care, NSAIDs for joint pain; monitor renal function
  • Drug-induced thrombocytopenia: discontinue offending agent, supportive care
  • HUS: supportive care, dialysis if needed; avoid antibiotics in typical (STEC) HUS
  • Vasculitis: rheumatology consultation, may require immunosuppression

Disposition

Admit

  • Fever with petechiae/purpura and ill appearance
  • Suspected meningococcemia, TTP, HUS, DIC
  • Severe thrombocytopenia (<20,000) or active bleeding
  • New diagnosis requiring urgent workup (possible leukemia, aplastic anemia)
  • Hemodynamic instability

Discharge

  • Well-appearing child with petechiae above the nipple line (mechanical cause — coughing, vomiting), normal CBC, and no fever
  • Known stable ITP with platelet count at baseline and no bleeding
  • Chronic/known vasculitis with mild flare — arrange outpatient follow-up
  • Return precautions: fever, spreading rash, bleeding, altered mental status, worsening symptoms

See Also

References

  1. ↑ Nguyen T and Freedman J. Dermatologic Emergencies: Diagnosing and Managing Life-Threatening Rashes. Emergency Medicine Practice. September 2002 volume 4 no 9.
  2. ↑ Thomas et al. Validating clinical practice guidelines for the management of children with non-blanching rashes in the UK (PiC): a prospective, multicentre cohort study, The Lancet Infectious Diseases, 2020, https://doi.org/10.1016/S1473-3099(20)30474-6
  3. ↑ Tessa Davis. Petechiae in Children – the PiC Study, Don't Forget the Bubbles, 2020. Available at: https://doi.org/10.31440/DFTB.30782
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