Diagnose on Sight: Bilateral Leg Rash
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Erythema nodosum, secondary to coccidioidomycosis
Erythema nodosum is a cutaneous reaction consisting of inflammatory, tender erythematous subcutaneous nodular lesions. The classically painful rash is located on the lower extremities and usually regresses spontaneously. It is associated with a wide variety of disease processes1,2 including:
- Most common cause: Streptococcal infections
- Other causes:
- Behcet’s syndrome
- Oral contraceptive use
- Viral infections
Coccidioidomycosis is endemic to certain arid parts of the Southwest United States. Erythema nodosum is the most characteristic reactive cutaneous manifestation of coccidioidomycosis. It presents 1-3 weeks after onset of illness and is usually self-limited.3 While strep infections are the most common cause of erythema nodosum, in a patient who has recently visited the American southwest, suspect coccidioidomycosis.
Master Clinician Bedside Pearls
Stuart Swadron, MD – Professor of Emergency Medicine, Keck School of Medicine of the University of Southern California (provided to ALiEM and recorded by Swadron, 2014)
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