Plaque
A plaque is a raised area of skin that is broad relative to its height, with a flat or slightly domed top. The word describes shape alone, and it is used most often when a condition produces patches larger than a papule.
Shape is all this word conveys. A plaque is raised above the surrounding skin and wide in relation to how far it rises, which distinguishes it from a papule, small and raised, and from a patch, which differs in colour without being raised at all.
Because the term is purely descriptive, it appears across conditions with nothing else in common. Psoriasis is the most familiar user of it, to the point where plaque psoriasis is the name of a pattern, but eczema, fungal infections and a number of other conditions produce plaques too.
What clinicians then describe is everything around the shape, and those details carry the diagnostic weight. Borders may be well demarcated, ending abruptly against normal skin, or ill defined, fading gradually. The surface may be scaly, smooth, thickened or fissured. Scale itself gets characterised: silvery and adherent suggests something different from greasy and yellowish.
Distribution then completes the picture, since where plaques appear on the body narrows the field considerably.
Hearing the word in a consultation therefore tells you what something looks like and nothing about what it is. The qualifiers that follow it are where the reasoning lives, which makes them worth listening for.
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