Diagnosis begins with a thorough history in which the physician may ask about family members with psoriasis, recent stressful events or illnesses, and initiation of new medications.  Next, he/she will perform a physical examination of the skin, hair, and nails to look for red, white, or silvery raised areas of thick, dry, flaky skin on the elbows, knees, trunk, scalp and other areas as well as characteristic nail abnormalities such as thickening, indentations, discoloration, loosening of the nail beds. Finally, to confirm the diagnosis, a biopsy may be performed to look at a small sample of skin under the microscope.