Purpura fulminans

Definition

Purpura fulminans is a rare, rapidly progressive and often fatal, highly thrombotic form of disseminated intravascular coagulation (DIC). Thrombotic occlusion of small and medium-sized vessels leads to skin necrosis, shock and multi-organ failure – a dermatological and haematological emergency.

Classification

• Neonatal form: fewer than 1 in 1,000,000 births; severe congenital protein C or protein S deficiency; onset hours to days after birth.
• Acute infectious form (most common): in severe infections and sepsis, including meningococci, streptococci, Staphylococcus aureus, Haemophilus and Clostridia.
• Idiopathic (post-infectious) form: 7–10 days after an infection (especially group A streptococcus, varicella) due to autoantibodies against protein S.

Occurrence & epidemiology

Children are most often affected, with two peaks at 1–3 and 16–18 years of age; adults can also be affected.

Aetiopathogenesis

The basis is a shift of haemostasis towards coagulation; in the infectious form, impaired protein C function or acquired protein C deficiency, among other factors, is implicated. Microvascular thrombosis causes the skin necrosis.

Clinical features

• Onset with skin pain, erythematous macules and petechiae, followed by ecchymoses and painful indurated purpuric plaques with erythematous borders.
• Classically retiform purpura with branched or angular lesions, particularly on the extremities.
• Within 24–48 hours haemorrhagic blisters and full-thickness skin necrosis.
• Systemically sepsis with or without shock, sometimes meningeal signs. Mortality of meningococcal disease complicated by purpura fulminans is 20–60%; survivors often have amputations and extensive scarring.

Diagnosis

• Clinical (acute, widespread retiform purpura); urgent skin biopsy to exclude other causes; blood or tissue cultures to identify the organism.
• Laboratory: thrombocytopenia, prolonged clotting times, decreased fibrinogen, elevated D-dimer; measurement of protein C, protein S and antithrombin III.

Differential diagnoses

• Necrotizing fasciitis
• Antiphospholipid syndrome – skin manifestations (livedo racemosa, Sneddon syndrome)
• Warfarin-induced skin necrosis (coumarin necrosis)
• Erythema nodosum

Keep learning in the app

References (selection)

1. DermNet: Purpura fulminans
2. DermNet: Retiform purpura
3. PubMed: Purpura Fulminans: Mechanism and Management of Dysregulated Hemostasis (PMID 29157918)
4. PubMed: Purpura fulminans: a dermatological emergency revisited (PMID 40795257)

Cross-references