Systemic Disease and Dermatologic Emergencies
Skin as a window
Many systemic diseases announce themselves in the skin. Emergency questions test recognition speed and first action.
Concepts to master
- Emergencies: SJS/TEN, angioedema with airway compromise, necrotizing fasciitis (pain out of proportion, crepitus, rapid spread), meningococcemia (purpuric rash with fever), and erythroderma.
- Paraneoplastic and systemic associations: acanthosis nigricans (insulin resistance, gastric malignancy), dermatomyositis (malignancy), acquired ichthyosis, and flushing syndromes.
- Vasculitis: palpable purpura on the lower extremities suggests leukocytoclastic vasculitis; evaluate for systemic involvement.
- Diabetes and thyroid disease: necrobiosis lipoidica, diabetic dermopathy, and pretibial myxedema.
- Mastocytosis and anaphylaxis: urticaria pigmentosa with Darier sign.
Traps
Necrotizing fasciitis can look deceptively benign early - pain out of proportion to findings is the clue, and imaging should not delay surgical debridement. Purpura with fever in a child is meningococcemia until proven otherwise. Erythroderma is a syndrome, not a diagnosis: it requires a search for the underlying cause (psoriasis, eczema, lymphoma, drug).
Worked example
A patient with fever, rapidly spreading erythema, exquisite pain, and crepitus after a minor injury. Diagnosis: necrotizing fasciitis. The correct action is immediate surgical consultation and debridement with broad-spectrum antibiotics - not outpatient oral therapy and not waiting for imaging.
Rule of thumb
In any dermatologic emergency, the first question is whether the airway, hemodynamics, or skin barrier is threatened. If yes, stabilize and involve the relevant specialty before completing the diagnostic workup.