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psoriasis

(Science: dermatology) A common chronic, squamous dermatosis, marked by exacerbations and remissions and having a polygenic inheritance pattern. The most distinctive histological findings in well developed psoriasis are Munro microabscesses and spongiform pustules.

It is characterised clinically by the presence of rounded, circumscribed, erythematous, dry scaling patches of various sizes, covered by greyish white or silvery white, umbilicated and lamellar scales, which have a predilection for the extensor surfaces, nails, scalp, genitalia and lumbosacral region. Central clearing and coalescence of the lesions produce a wide variety of clinical configurations, including annular or circinate, discoid or nummular, figurate and gyrate arrangements.

Origin: Gr. Psoriasis A chronic skin disease characterized by dry red patches covered with scales; occurs especially on the scalp and ears and genitalia and the skin over bony prominences.A disease of the skin causing it to go red, dry and flaky which is believed to result from deficiencies in the immune system of the sufferer.