Makindo Medical Notes

Definition and Classification

Purpura fulminans is defined by the sudden onset of widespread purpura (bruising) that evolves into hemorrhagic necrosis. It is typically classified into three main types based on the underlying cause:

• Acute Infectious Purpura Fulminans: The most common form, often triggered by severe bacterial infections (e.g., Neisseria meningitidis) or viral infections (e.g., varicella). It is frequently seen in children under 7 years old, particularly following an upper respiratory tract infection or in patients with asplenia.
• Neonatal Purpura Fulminans: Occurring in newborns, usually related to congenital deficiencies of natural anticoagulants, such as protein C or protein S.
• Idiopathic Purpura Fulminans: A less common form that can occur without an identifiable infectious trigger and may be associated with autoimmune disorders.

Pathophysiology

The underlying mechanism of purpura fulminans involves intravascular thrombosis and hemorrhage. In acute infectious cases, endotoxins from the infectious agent trigger an imbalance between procoagulant and anticoagulant factors, notably leading to a deficiency in protein C. This imbalance causes widespread microvascular thrombosis, resulting in tissue ischemia and necrosis. The ensuing cutaneous damage appears as rapidly progressing hemorrhagic lesions.

Clinical Features

The clinical presentation of purpura fulminans includes:

• An initial petechial rash that rapidly evolves into confluent ecchymoses and hemorrhagic bullae.
• Necrosis of the skin with well-demarcated lesions and the formation of hard eschars.
• Systemic signs such as fever, septic shock, and disseminated intravascular coagulation.
• Extensive tissue loss that, in severe cases, may lead to limb amputation.

Management and Prognosis

Purpura fulminans is a surgical and medical emergency. The management strategy includes:

• Resuscitation: Immediate fluid resuscitation and stabilization of the patient's hemodynamic status.
• Antibiotic Therapy: Prompt administration of broad-spectrum antibiotics to address the underlying infection. Blood cultures and swabs for sensitivity should be taken prior to initiating therapy.
• Surgical Intervention: Urgent debridement of necrotic tissue until viable, healthy, bleeding tissue is reached. Early surgical review and subsequent debridement, along with the use of vacuum-assisted dressings, are often necessary. In selected cases, early skin grafting may help reduce protein and fluid losses.

Despite aggressive treatment, the mortality rate for purpura fulminans remains high—ranging from 30% to 50%—largely due to rapid progression to multiorgan failure and septic shock.