Which symptom is a key feature of erythema nodosum?

A key feature of erythema nodosum is the presence of painful, raised red nodules. Erythema nodosum is an inflammatory condition that primarily affects the subcutaneous fat tissue, typically resulting in bilateral, tender nodules that can vary in color from reddish to purplish. These nodules often appear on the lower legs and may be associated with systemic symptoms such as fever and malaise.

The other conditions associated with the incorrect answers involve different characteristics and clinical presentations. Scaly patches on the scalp are indicative of conditions like psoriasis or seborrheic dermatitis. Blisters filled with clear fluid suggest a condition such as herpes simplex virus infection or pemphigus, while white plaques in the mouth are commonly associated with oral thrush or leukoplakia. Each of these presentations varies distinctly from the painful nodules characteristic of erythema nodosum.