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 2% of population 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 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 results from exposure of dermal papillae 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 for all patients Medical topical corticosteroids indication first-line and often used in combination with topical calcipotriene topical calcipotriene (vitamin D analog) indication first-line and often used in combination with topical corticosteroids systemic non-biologic therapies indication moderate-to-severe psoriasis used in combination with topical therapies drugs acitretin methotrexate cyclosporine apremilast especially for those with psoriatic arthritis as well systemic biologic therapy indication moderate-to-severe psoriasis drugs tumor necrosis factor inhibitors adalimumab etanercept infliximab anti-interleukin agents secukinumab ustekinumab narrowband ultraviolet B indications for patients who are contraindicated to systemic therapy Complications Psoriatic arthritis Other HLA-B27 associated autoimmune diseases