In psoriasis, lesions typically appear on which type of skin surface?

In psoriasis, lesions predominantly manifest on extensor surfaces of the body, which are areas commonly exposed, such as the elbows, knees, and scalp. These lesions may appear as well-defined, red plaques covered with silvery scales. The mechanism underlying the appearance of these lesions is related to the accelerated turnover of skin cells, which results in the characteristic buildup and scaly appearance.

Extensor surfaces are particularly affected due to the nature of the skin in these areas, where it tends to be thicker, and the immune response leading to psoriasis is often more pronounced. The chronic inflammation associated with the disease can lead to both the symptoms of lesions and the accompanying discomfort.

In contrast, flexor surfaces, mucosal surfaces, and hair-covered surfaces tend to be less commonly involved in psoriasis. Flexor surfaces, such as the inner elbows or behind the knees, may be more susceptible to other skin conditions like eczema. Mucosal surfaces generally do not exhibit the same types of lesions characteristic of psoriasis, and while psoriasis can occur on the scalp (which is hair-covered), the signature plaques are much more typical in the extensor regions.