Clinical Presentations

Psoriasis can start at any age, although the most common times are in the teens and in the forties and fifties. There is often a family history. About 3% of people develop psoriasis at some time in their lives. Children may present with ‘guttate’ (drop-like) psoriasis (Figure 12.1), multiple small red scaly areas, a few days after streptococcal throat infection.

There are multiple areas of red, slightly raised and scaly skin ‘plaques’ (Figures 12.2 and 12.3). Plaques have a clear edge and are often symmetrical. If scratched, they bleed more easily than normal skin. Knees, elbows and scalp are often affected, but all areas can be involved (Figure 12.4). Lesions last many months or years, may slowly enlarge and coalesce and can be itchy. Patients are most concerned by the appearance, the scales and the huge impact that the disease can have on their lives.

When the groin, axillae or other body folds are affected, the scale comes off easily in these moist areas so there is a shiny red appearance (Figure 12.5). Often, the fingernails are affected, with multiple small pits, discoloration and thickening (Figure 12.6). Toenails are also affected and can look like fungal infection.

Scalp psoriasis (Figures 12.7 and 12.8) can be felt better than seen, although if you part the hair, you see grey matted scale instead of normal scalp skin. Scalp psoriasis has a clear edge, typically with some areas unaffected, in contrast to dandruff that affects the whole scalp.

Rarely, the psoriasis becomes very extensive, with most of the skin becoming red and scaly (erythrodermic, Figure 12.9). This leads to:

Increased fluid loss through the skin
Increased protein loss
Mild heart failure, as 25% of the cardiac output may be diverted to the skin
Although the skin feels hot, there is great heat loss from radiation, resulting in hypothermia.

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