American Nurses Credentialing Center (ANCC) Practice Exam

The presentation of a well-circumscribed erythematous plaque with scales is highly indicative of psoriasis. This condition commonly manifests as red patches covered by thick, silvery scales, which occur due to the rapid turnover of skin cells. The well-defined borders of the plaque are characteristic, and the scaling aspect is a hallmark feature that helps differentiate psoriasis from other dermatoses.

Psoriasis is associated with various forms, including plaque psoriasis, which is the most common type. In contrast, ichthyosis typically presents with dry, scaly skin but does not usually feature the well-defined red plaques seen in psoriasis. Atopic dermatitis typically appears as itchy, inflamed skin, often with a more diffuse pattern rather than the well-circumscribed plaques found in psoriasis. Tinea corporis, or ringworm, is a fungal infection characterized by annular lesions and is also distinct from the presentation of psoriasis, especially with regard to the absence of scale prominence and the different border characteristics.

Thus, the well-circumscribed, erythematous plaque with scaling aligns most closely with the diagnosis of psoriasis, making it the most likely condition in this scenario.