Rectangular single-plaque psoriasis: a report of two cases in Yemen

Psoriasis is a commonly occurring immune-mediated chronic dermatosis that affects 2–3% of the world's population. Patients usually present with multiple plaques distributed across the trunk. In rare cases, patients have a few plaques, and in rarer cases, patients have plaques on just one side of the body. Psoriasis manifesting as a single plaque is extremely rare, with only one case reported to date. Plaques are usually round or oval; however, to the best of our knowledge, no case of a rectangular plaque has been reported. Herein, we present two cases of rectangular, single-plaque psoriasis: one on the right upper arm of a female patient and another on the right buttock of a male patient. In both cases, the diagnosis was based on typical clinical presentations. The patients were treated with topical clobetasol ointment, which resulted in excellent improvement. The present case series highlights the importance of considering single-plaque psoriasis as part of the differential diagnosis when a scaly plaque presents as a solitary lesion.