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INTRODUCTION TO CHAPTER
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Psoriasis, seborrheic dermatitis, pityriasis rosea, and lichen planus are diseases that present with papulosquamous lesions (scaly papules and plaques). Although these diseases may have a similar morphology, their underlying etiologies vary. Secondary syphilis, cutaneous T cell lymphomas, and connective tissue disease may also present with papulosquamous lesions and should be included in the differential diagnosis.
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✓ Psoriasis is a common, chronic inflammatory disease that typically presents with scaly red to salmon pink plaques on the elbows, knees, scalp, lower back, and gluteal cleft.
✓ About 1/3 of patients with psoriasis will develop psoriatic arthritis during their lifetime.
✓ Cardiometabolic disease, gastrointestinal diseases, kidney disease, and mood disorders are common comorbidities in patients with psoriasis.
✓ Most patients with mild to moderate psoriasis can be managed with topical medications and/or phototherapy.
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Psoriasis is a common, chronic, inflammatory, immune-mediated disease. Clinicians and patients have long been vexed by this ancient affliction. Although most medical literature prior to Willan (1757–1812) lumped psoriasis, leprosy, eczema, and other inflammatory dermatoses into a confusing menagerie, Celsus gave a convincing account of psoriasis vulgaris almost 2,000 years ago. His description included many of the morphologic features that physicians today utilize to diagnose psoriasis, including: the "ruddy" or salmon-colored plaques with silvery scales that often are associated with punctate hemorrhage or "erosions" when removed.1
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More than 7.5 million adults (2.1% of the population) in the United States are affected and 30% of these individuals will develop psoriatic arthritis.2 About 1.5 million patients are considered to have moderate to severe disease.
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Psoriasis may have a significant negative impact on the patient's quality of life. Patients often are self-conscious, depressed, or frustrated over the appearance of their skin. Studies have found that between 5 and 10% of psoriasis patients suffer from depression, anxiety, and other mental health comorbidities.3
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Psoriasis spans all socio-economic groups, and its prevalence varies by geographic location. Historically, the disease is more common in the northern latitudes. The rate of psoriatic disease is lower in African-Americans compared to European-Americans.2
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The primary cause of psoriasis is dysregulation of the cell mediated, adaptive immune response, but a genetic predisposition along with environmental triggers are also postulated to play a role. A positive family history for psoriasis can be found in 35% of patients4 and HLA-Cw6 is a well-researched gene implicated in psoriasis.
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The dysregulation seen in psoriasis is likely triggered by hyperactivity of the innate immunological surveillance system to environmental antigens. In genetically predisposed individuals, the Th1 pathway response is over-stimulated and this overproduction of Th1 related cytokines along with interleukin -12, 17, and 23 causes hyper-proliferation of epidermal keratinocytes. These events lead to the formation of ...