Genetically determined (sporadic) common, chronic, epidermal proliferative disease. Clinically characterized by erythematous, dry scaling patches, recurring remissions and exacerbations. Flares may be related to systemic and environmental factors. Usual course - acute, chronic; unpredictable.
- Clinical forms:
- Discoid or plaque psoriasis - most common, patches appear on scalp, trunk and limbs, nails may be pitted and/or thickened
- Guttate psoriasis - occurs most frequently in children, numerous small papules over wide area of skin, but greatest on the trunk
- Pustular psoriasis - small pustules over the body or confined to one area (i.e., palms and soles) or arranged in annular patterns (especially children)
- Inverse, flexural psoriasis - affects the flexural areas, lesions are moist and without scales (common in older people)
- Erythroderma (exfoliative psoriasis or red man syndrome) - patients skin turns red, may result from a flare of pre-existing dermatosis
- Ostraceous - grossly hyperkeratotic
- System(s) affected: Skin/Exocrine
- Genetics:
- Genetic predisposition (probably polygenic)
- Type I psoriasis - young, strong family history = more aggressive disease
- Type 2 psoriasis - older, no family history = more stable disease
- Higher incidence in Caucasians and atopic families
- Increased incidence of human leukocyte antigens (HLA antigens)
- Incidence/Prevalence in USA: 1000-2000 cases/100,000 people in the U.S.
- Predominant age: Two peaks of onset, age 16-22 and age 57-60; can develop in infants
- Predominant sex: Male = Female