Psoriasis

Resumen

Psoriasis is a common, chronic inflammatory skin condition that occurs as part of a complex set of interactions between genetic, immunological, systemic and environmental factors(Schofield et al 2009). Diagnosis of psoriasis is made by clinical assessment rather than laboratory testing. The condition is characterised by well-demarcated red, silvery, dry, raised, scaly plaques andfollows an unpredictable pattern of relapses and periods of remission (Smith et al 2009). The plaques form as a result of hyperproliferation of the epidermis, vascular proliferation and inflammation. Theterm epidermal hyperproliferation refers to the thickening of the skin, which occurs as a result of the skin replacing itself too quickly. In psoriatic skin, the transit time of the epidermal cells(keratinocytes) maturing from the basal layer to the stratum corneum is more rapid than in normal skin. The transit time in psoriatic skin is about four days, compared with about 28 days in normal skin(Hughes and Van Onselen 2001). Within the dermis, the capillaries become dilated and an infiltrate of white blood cells envelops them; this, along with the epidermal hyperproliferation, produces thecharacteristic erythema (redness), inflammation and silvery scaly appearance. These processes are driven largely by activated T cells or antigen presenting cells. This activity triggers the release ofchemokines and cytokines which induce the keratinocyte hyperproliferation (Hughes and Van Onselen 2001). Common sites of psoriatic plaques include the extensor surfaces of the knees and elbows, lowerback or sacrum, scalp and nails, although plaques can affect the whole body. The severity of the condition can vary dramatically, from one or two small plaques to extensive coverage of more than 90%of the body’s surface area (British Association of Dermatologists (BAD) 2009).


Resumen informativo alternativo

La psoriasis es una enfermedad inflamatoria crónica de la piel que afecta a...