Diagnose on Sight: Bilateral Leg Rash

Case: A pre-teen girl, living in central California, recently started on fluconazole, now presenting with a bilateral leg rash. What is your diagnosis? Click on the image for a larger view.

Poll Results

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Erythema nodosum, secondary to coccidioidomycosis

Explanation

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 processes^1,2 including:

• Most common cause: Streptococcal infections
• Other causes:
  • Behcet’s syndrome
  • Oral contraceptive use
  • Pregnancy
  • Sarcoidosis
  • Tuberculosis
  • 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.

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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)

Author information

Jeff Riddell, MD

Assistant Professor of Clinical Emergency Medicine
Co-Director, Medical Education Fellowship
LA County + USC Emergency Medicine Residency, Department of Emergency Medicine
Keck School of Medicine of the University of Southern California

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