Clinical exam can provide clues; KOH examination can reveal the Dx
The differential diagnosis for an annular skin lesion includes not only tinea corporis, but also superficial erythema annulare centrifugum, pityriasis rosea, granuloma annulare, subacute cutaneous lupus erythematosus (SCLE), and nummular eczema.
Superficial erythema annulare centrifugum, like tinea corporis, has scale. But the location of the scale sets the 2 apart. Superficial erythema annulare centrifugum lesions have a central trailing scale, whereas tinea corporis lesions have a peripheral leading scale.4
Pityriasis rosea forms multiple lesions in a “Christmas tree” pattern on the trunk, sometimes beginning with a single herald patch. Our patient’s single lesion with concentric scaly rings was inconsistent with the distribution and quality of the lesions in pityriasis rosea.4
Granuloma annulare lesions are smooth, nonscaly plaques that are most often seen on the dorsal hands and feet. The scaly manifestation of our patient’s lesion was not consistent with this diagnosis.4
SCLE lesions are typically photodistributed on sun-exposed skin (eg, the neck, upper trunk, or arms), whereas our patient’s lesion involved a sun-protected site.4
Continue to: Nummular eczema