Board Review: Dermatologic Emergencies

Overview / Definition Dermatologic emergencies are acute skin conditions that pose immediate risks to the patient's health and require prompt recognition and intervention. Common emergencies include Steven-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, uticaria, and acute infections like cellulitis and necrotizing fasciitis. Epidemiology While the exact incidence of dermatologic emergencies varies, certain conditions have notable prevalence rates: Steven-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) occur in approximately 1-2 cases per million person-years. Acute urticaria affects about 20% of the population at some point in their lives. Necrotizing fasciitis has an incidence of 0.4-1.3 per 100,000 person-years. Pathophysiology / Mechanism The pathophysiology of dermatologic emergencies varies based on the specific condition: Steven-Johnson syndrome: Triggered by medications or infections, leading to keratinocyte apoptosis and extensive skin detachment. Necrotizing fasciitis: Often initiated by bacterial infection (e.g., group A Streptococcus), leading to rapid tissue necrosis. Urticaria: Mediated by histamine release from mast cells in response to allergens. Clinical Presentation Recognizing the clinical features of dermatologic emergencies is critical: Steven-Johnson syndrome: Flu-like symptoms followed by painful mucosal erosions and skin detachment. Toxic epidermal necrolysis: Extensive epidermal detachment, >30% body surface area, often with systemic symptoms. Necrotizing fasciitis: Rapidly progressing erythema, swelling, and systemic signs of infection. Urticaria: Raised, itchy wheals that can vary in size, often with angioedema. Diagnosis / Workup The diagnosis of dermatologic emergencies often requires careful clinical evaluation and may include: History and physical examination to identify trigger factors. Skin biopsy for conditions like SJS/TEN to confirm diagnosis. Laboratory tests: CBC, blood cultures, and imaging studie