Chronic plaque psoriasis |
Figure 8.1 Plaque psoriasis. (Source: Reprinted from
Graham-Brown and Burns, 2006.) |
This is the most common form accounting for about 80% of those with psoriasis. Also known as psoriasis vulgaris, where vulgaris means common, it is characterised by well circumscribed, scaly plaques. These plaques can range in shape (although they are usually round or oval) and size from millimetres in diameter to many centimetres (Figure 8.1). The most common sites are extensor surfaces, i.e. elbows and knees, the lower back or sacrum, natal cleft, genitalia and the scalp. More-often-than-not the lesions are symmetrical, i.e. they appear on both knees or both elbows; however, the lesions on each side are not necessarily identical. Psoriasis often occurs on the hairline and can creep down over the forehead, down the neck and into and around the ears. In reality plaques can occur anywhere, although appearance on the face is considered rare.
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Figure 8.2 Inverse psoriasis. (Source: Reprinted
from Weller et al., 2008.) |
If chronic plaque psoriasis (CPP) occurs in flexural areas, the appearance will be quite different from other areas of the body. Because of the heat and occlusive nature of flexures, the scale rubs off leaving a bright red shiny area of skin. There may be a fungal or bacterial infection present along with the psoriasis. This type of psoriasis is sometimes known as inverse psoriasis (Figure 8.2).
CPP on hands and feet (palmar/plantar psoriasis) also has a somewhat different appearance. Individual plaques may not be seen, but thickened fissured skin, often more apparent on the dominant hand, will be in evidence. In order to distinguish this from a contact dermatitis for example, a careful history and an assessment for psoriasis on other parts of the body, for example in the nails, is needed.
When psoriasis occurs in the scalp, the scaling can become particularly thickened as the hair prevents the scale from shedding (Figure 8.3). As the scale develops it can cover the whole scalp which feels tight and uncomfortable; it has been described as feeling like wearing a swimming cap. Although hair loss may seem more extensive than normal, this is not permanent and patients can be reassured that hair will grow back.
