Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by raised areas of abnormal skin. These areas are red, or purple on some people with darker skin, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete body coverage. Injury to the skin can trigger psoriatic skin changes at that spot, which is known as the Koebner phenomenon.The five main types of psoriasis are plaque, guttate, inverse, pustular, and erythrodermic. Plaque psoriasis, also known as psoriasis vulgaris, makes up about 90% of cases. It typically presents as red patches with white scales on top. Areas of the body most commonly affected are the back of the forearms, shins, navel area, and scalp. Guttate psoriasis has drop-shaped lesions. Pustular psoriasis presents as small, noninfectious, pus-filled blisters. Inverse psoriasis forms red patches in skin folds. Erythrodermic psoriasis occurs when the rash becomes very widespread, and can develop from any of the other types. Fingernails and toenails are affected in most people with psoriasis at some point in time. This may include pits in the nails or changes in nail color.Psoriasis is generally thought to be a genetic disease that is triggered by environmental factors. If one twin has psoriasis, the other twin is three times more likely to be affected if the twins are identical than if they are nonidentical. This suggests that genetic factors predispose to psoriasis. Symptoms often worsen during winter and with certain medications, such as beta blockers or NSAIDs. Infections and psychological stress can also play a role.
The parents of a child with an autosomal recessive disorder are carriers of one copy of the defective gene, but are usually not affected by the disorder.The prevalence of mutations associated with this condition reach 68% to 81% in certain arctic coastal populations, suggesting that the condition had some adaptive value in those habitats at some time. Fewer than 50 people have been identified with this condition. Diagnosis
Genetic testing is necessary for diagnosis. Differential diagnosis
This condition is sometimes mistaken for fatty acid and ketogenesis disorders such as Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCAD), other long-chain fatty acid oxidation disorders such as Carnitine palmitoyltransferase II deficiency (CPT-II) and Reye syndrome. Treatment
Treatment for this condition is supportive. There is no cure. Affected people should eat a high-carbohydrate, low-fat diet and avoid fasting. See also
Primary carnitine deficiency
Carnitine palmitoyltransferase II deficiency

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This article incorporates public domain text from The U.S. National Library of Medicine