Skill Checkup: A 27-Year-Old Woman With Erythematous Plaques on Her Elbow, Thighs, and Scalp

William James, MD


December 20, 2021

Figure 1. Close-up of pink- and grey-colored psoriasis plaques. Psoriasis is one of the most common skin disorders. It involves a 10-fold increase in the speed of epidermal cell proliferation, normally at localized sites at the elbows, forearms, knees, and scalp. It is characterized by well-defined plaques, the color of which varies from red to silver. More extreme cases can affect the whole body, causing considerable disability. While there is no cure, treatment can help keep symptoms under control.

This patient's lesions are typical of those of plaque psoriasis. This condition is characterized by raised, inflamed lesions covered with a silvery white scale. The scale may be scraped away to reveal inflamed skin beneath. The lesions have a characteristic look, with sharply demarcated margins. The plaques are irregular to oval and are most often located on the scalp, trunk, and limbs, with a predilection for extensor surfaces such as the elbows and knees. Smaller plaques may coalesce into larger lesions, especially on the legs and sacral regions. Fissuring within plaques can occur when lesions are present over joint lines or on the palms and soles.

The diagnosis of psoriasis is clinical, based primarily on the findings described above. There is no specific or diagnostic blood test or imaging procedure for diagnosis of psoriasis. Skin biopsy can confirm the diagnosis, but this procedure is usually reserved for the evaluation of atypical cases or for excluding other conditions in cases of diagnostic uncertainty.


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