Snapshot A 42-year-old man presents to his dermatologist for management of his psoriasis. He reports an itchy and rough rash along his elbows, knees, and scalp. While he was previously treated for this disease in childhood, he has been off treatment for years. Physical exam reveals 2-7 cm pink plaques with overlying silvery scales. When the scale is scratched off, there is pinpoint bleeding. He is started on an intensive topical therapy regimen with corticosteroids and vitamin D analog. Introduction Clinical definition idiopathic and chronic inflammatory disease characterized by silver scales and thickened skin most common subtype is plaque psoriasis Epidemiology incidence US incidence login to view 1 more bullet demographics normallly, > 40 years of age but can affect people of all ages risk factors smoking skin trauma alcohol abuse stress cold weather Etiology idiopathic drugs Pathogenesis hyperproliferation of basal stem keratinocytes ↑ inflammation, especially inflammatory markers IL-6, C-reactive protein, TNF-α, E-selectin, ICAM-1 Associated conditions psoriatic arthritis Presentation Fingernails seen in psoriasis Symptoms painful or pruritic skin lesions joints may be painful or stiffens especially in feet and hands Physical exam well-circumscribed, pink papules and flat-topped plaques with silvery scales common locations scalp trunk buttocks extensor surface of limbs positive Auspitz sign when scales are scraped off, there is pinpoint bleeding login to view 1 more bullet nail pitting Studies Labs electrolytes there may be electrolyte imbalances if psoriasis is extensive Histology acanthosis with parakeratosis (thickened stratum corneum with retained nuclei) Munro microabscesses ↑ stratum spinosum ↓ stratum granulosum Differential Atopic dermatitis Seborrheic dermatitis Treatment Conservative emollients indication login to view 1 more bullet Medical topical corticosteroids indication login to view 1 more bullet topical calcipotriene (vitamin D analog) indication login to view 1 more bullet systemic non-biologic therapies indication login to view 2 more bullets drugs login to view 5 more bullets systemic biologic therapy indication login to view 1 more bullet drugs login to view 7 more bullets narrowband ultraviolet B indications login to view 1 more bullet Complications Psoriatic arthritis Other HLA-B27 associated autoimmune diseases