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?
Allergic contact dermatitis Atopic dermatitis Psoriasis Lichen planus