What is a common physical finding in psoriasis vulgaris?

The presence of well-demarcated plaques and coalescing papules on the knees is a hallmark feature of psoriasis vulgaris. This condition is characterized by the formation of thick, red, scaly patches on various areas of the body, with common locations being the elbows, knees, scalp, and lower back. The "well-demarcated" nature of the plaques refers to how distinctly the borders of the lesions appear against the surrounding skin, making them easily identifiable. Coalescing papules indicate that individual lesions can merge together to form larger plaques, which is typical in psoriasis as the disease progresses.

The other options do not accurately represent the physical findings associated with psoriasis vulgaris. For instance, lichenification typically occurs as a result of chronic scratching or irritation, which is more characteristic of conditions like eczema rather than psoriasis. Additionally, maculopapular lesions may suggest various other dermatological conditions and are not specific to psoriasis, while scaling lesions within the nasolabial folds are more commonly associated with seborrheic dermatitis or other skin conditions rather than psoriasis vulgaris. Thus, the description of well-demarcated plaques and coalescing papules on the knees aligns perfectly with the clinical presentation expected in a patient with psoriasis vulgaris