(BMJ)—A woman in her 20s presented w/ a 3-yr hx of rash on her trunk and both legs. Exam: annular, scaly, red plaques w/ glossy surfaces; nail pitting. Bleeding points were visible after the scales were removed (Auspitz sign). What’s the dx?
Annular plaque-type psoriasis
Erythema annulare centrifugum
Granuloma annulare
Nummular eczema
Tinea corporis
You are correct. This pt has annular plaque-type psoriasis (APTP). Although normal psoriatic plaques can have an annular appearance w/ central clearing secondary to topical tx, APTP manifests as rare, primary, annular plaques before any tx. APTP occurs in all ages, w/ a relatively higher proportion in people <20 yo. APTP is more common on the trunk, arms, and legs. The prognosis is similar to that of mild psoriasis. Auspitz sign, microscopic exam for fungi, and histopathology can help differentiate APTP from tinea corporis and granuloma annulare.

BMJ 2020;371:m3974