The most common type of psoriasis -- plaque psoriasis -- usually appears as red, raised patches of skin covered in white, flaking scales that crop up on the knees, elbows, scalp, hands, feet, or lower back. Those with psoriasis may also experience itching, nail disfigurement (about half of people with the disease experience discoloration, separation from the nail bed, or thickened or pocked nails), and dry or cracked skin that can bleed.