Annular plaques on the back and flanks

Annular psoriasis is characterized by ring-shaped patches with white micaceous scaling and central clearing. Topical steroid use may be responsible for the central clearing as scaled patches expand. This rash can appear in places EAC typically does not, such as on the scalp, elbows, and knees.

Pityriasis rosea starts with a solitary herald patch a few days before hundreds of small oval scaled patches appear on the trunk in a “fir tree” distribution. Unlike EAC, the herald patch does not show the trailing scale.

The rash associated with the secondary stage of syphilis can appear on the soles of the feet and palms, which differs from EAC because EAC typically spares the feet and hands.

In the patch stage of mycosis fungoides, the ring-shaped rash can appear similar to psoriasis or chronic eczema, but can sometimes last years to even decades. Unlike EAC, these rings do not show a trailing scale and the patches may demonstrate poikiloderma (erythema, atrophy, and dyspigmentation).

Fungi, viruses, ectoparasites, and, less commonly, certain medications can trigger erythema annulare centrifugum.

To treat EAC, eliminate the trigger

Treatment of EAC should focus on eliminating the inciting agent.² In one study of 66 patients with EAC, 42%, had a concomitant cutaneous fungal infection (tinea pedis, tinea corporis, or onychomycosis).³ A direct cause-and-effect relationship was established in 2 patients with dermatophyte-induced EAC whose lesions were reproduced and subsequently cleared by the experimental inoculation and treatment of tinea pedis.¹

Our patient. Four weeks of oral terbinafine 250 mg/d effectively cleared our patient’s case of tinea pedis and EAC. After 3 months of treatment with terbinafine the onychomycosis showed one-third clearing at the proximal nail fold. Without additional treatment, the nails were completely clear 8 months later.

CORRESPONDENCE
Robert T. Brodell, MD, Department of Dermatology, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216; rbrodell@umc.edu