Is this annular lesion a spider bite?

A 42-year-old woman suspects that this lesion on the dorsum of her foot is a brown recluse spider bite. The slowly progressive, tender, itchy, nonhealing lesion has been present for 2 weeks.

What is your tentative diagnosis—and your likely course of action?

A. Refer the patient to a plastic surgeon for wound debridement.

B. Initiate therapy with a broad-spectrum antibiotic.

C. Check the patient’s glucose-6-phosphate dehydrogenase (G6PD) status, and initiate dapsone therapy.

D. Perform a potassium hydroxide (KOH) evaluation.

E. Reassure the patient, and send her home.

(Answer on next page)

Answer: Ringworm

This lesion has the typical annular, erythematous, scaly appearan›ce of ringworm, a diagnosis that was confirmed by a KOH evaluation, D. Treatment with a topical antifungal preparation was initiated.

Had this been a brown recluse spider bite, surgery would have worsened the outcome. Antibiotics—except for dapsone—have no role in treating such bites. You could have reassured the patient that this was not a spider bite and sent her home, but she probably would have returned in short order for treatment of the persistent dermatophyte infection.