Purpura Fulminans

Purpura fulminans is a thrombotic subtype of DIC secondary to protein C deficiency and is characterised by:

The other two subtypes of purpura fulminans are:

  • Congenital
    Secondary to deficiency of Protein C, Protein S, or Antithrombin III.
  • Autoimmune
    Very rare, secondary to auto-antibody to Protein S.

Epidemiology and Risk Factors

Pathophysiology

Protein C deficiency can result from:

  • Consumption
    The classical DIC coagulopathy
  • ↓ Hepatic synthesis
    • ↑ Risk with acute liver injury
  • Destruction by elastase

Aetiology

Causes of Acute Purpura Fulminans
Infective Non-infective

Bacterial:

  • S. Pneumoniae
    Predominantly asplenic patients.
  • S. Pyogenes
  • S. Aureus
  • H. Influenzae
  • N. Meningitidis
    ~20%.
  • Endocarditis
  • Basically any other Gram negative

Viral:

  • VZV
  • West Nile virus

Fungal:

  • Aspergillus spp.
  • Cryptococcus neoformans
  • Fusarium spp.

Parasitic:

  • P. Falciparum malaria

Circulatory:

  • Vasopressor excess

Haematological:

  • MAHA
  • TTP
  • Warfarin-induced skin necrosis

Infective causes are significantly more common than non-infective causes.

Clinical Manifestations

Progressive skin changes:

Purpura Fulminans

  1. Initially non-blanching patchy rash
    • Mottling
    • Generally of extremities
  2. Skin necrosis
    • Within 24-48 hours
    • Black necrotic lesions
    • May be insensate
    • Haemorrhage into skin may cause bullae formation

Diagnostic Approach and DDx

Key differentials:

  • Haematological
    • Catastrophic antiphospholipid syndrome
    • Warfarin-induced skin necrosis
  • Vasculitis
    • HSP
  • Other
    • Necrotising fasciitis
    • Cocaine toxicity

Investigations

Bedside:

Laboratory:

  • FBE
    • Thrombocytopaenia
  • Coagulation
    • INR: 1-3
    • PTT: 1-3× ULN
    • Fibrinogen: Variable
  • D-dimer
    Significantly ↑.
  • Protein C
    <40% normal.

Imaging:

Other:

Management

  • Treat underlying cause
  • Consider anticoagulation

Specific therapy:

  • Pharmacological
    • Heparin
      • anti-Xa targeting due to confounding from APTT measurement
      • AT III supplementation may be considered but can result in dramatic ↑ in heparin effect
    • Blood product
      • Platelets >30
      • Fibrinogen >1
    • Avoid warfarin
      Due to ↓ protein C synthesis.
  • Procedural
  • Physical

Supportive care:

Disposition:

Preventative:

Marginal and Ineffective Therapies

Anaesthetic Considerations

Complications

  • E
    • Adrenal insufficiency secondary to adrenal haemorrhage
  • F
    • AKI
      Glomerular thrombosis.

Prognosis

Key Studies

References