A 20-year-old male presents with a rash on the scalp, (extensor) elbows, knees and umbilicus. The rash is sharply demarcated erythematous plaques with silvery scale in those locations; there is no central clearing. The soles of the feet are normal. What is the most likely diagnosis?

Psoriasis is chronic, immune-mediated inflammatory condition. Activation of T cells of the adaptive immune system, Th1 and Th17 cells, activate keratinocytes to proliferate and produce multiple chemokines and antimicrobial peptides. Genetic predisposition is present in Type1 Plaque psoriasis and Guttate psoriasis with HLA-C Initial Lesions Location of initial Lesions Other Findings Diagnostic Aids Treatment Psoriasis Pink-red, silvery scale, sharply demarcated Elbows, knees, scalp, presacral area, intergluteal fold Nail dystrophy, ahritis, pustules; SAPHO syndrome, especially with palmoplantar pustulosis Skin biopsy Topical glucocoicoids, Vitamin D; UV-B (narrowband) > PUVA (psoralen with UVA) Oral retinoid; MTX, Cyclosporine, Anti-TNF agents, anti-IL-12/23 Ab