Psoriasis
It is an idiopathic, immunologic, chronic skin inflammation, characterized by well-defined salmon-pink
plaques with adherent silvery attached scales, particularly on extensor surfaces. Affects 1-3% of
population 15-40 years of age, mostly European & northern americans
N.B: it can affect any part of the skin including nails, scalp, back, knees & elbows, but usually spares the
face.
Histologic changes: Hyperkeratosis & “Parakeratosis “nuclei retained in the corneium layer””
Irregular thickening of the epidermis & dilated, tortuous loops of capillaries in dermal papillae causing
bleeding when scale is scratched off “Auspitz sign”
Epidermal polymorphonuclear leucocyte infiltrates and microabscesses
Precipitating factors:
Trauma: can appear in skin damaged by scratches or surgical wounds “Kobner phenomenon”
Infection: tonsillitis caused by β-hemolytic streptococci often triggers guttate psoriasis
Hormonal: psoriasis frequently improves in pregnancy only to relapse postpartum
Sunlight: improves most psoriatics but 10% become worse
Drugs: antimalarials, β-blockers, IFN-α, anti-TNFα & lithium may worsen psoriasis. Psoriasis may
‘rebound’ after withdrawal of treatment with systemic steroids
Cigarette smoking and alcohol
Emotional stress
It is an idiopathic, immunologic, chronic skin inflammation, characterized by well-defined salmon-pink
plaques with adherent silvery attached scales, particularly on extensor surfaces. Affects 1-3% of
population 15-40 years of age, mostly European & northern americans
N.B: it can affect any part of the skin including nails, scalp, back, knees & elbows, but usually spares the
face.
Histologic changes: Hyperkeratosis & “Parakeratosis “nuclei retained in the corneium layer””
Irregular thickening of the epidermis & dilated, tortuous loops of capillaries in dermal papillae causing
bleeding when scale is scratched off “Auspitz sign”
Epidermal polymorphonuclear leucocyte infiltrates and microabscesses
Precipitating factors:
Trauma: can appear in skin damaged by scratches or surgical wounds “Kobner phenomenon”
Infection: tonsillitis caused by β-hemolytic streptococci often triggers guttate psoriasis
Hormonal: psoriasis frequently improves in pregnancy only to relapse postpartum
Sunlight: improves most psoriatics but 10% become worse
Drugs: antimalarials, β-blockers, IFN-α, anti-TNFα & lithium may worsen psoriasis. Psoriasis may
‘rebound’ after withdrawal of treatment with systemic steroids
Cigarette smoking and alcohol
Emotional stress
