In most cases, your primary care doctor or dermatologist will be able to diagnose psoriasis by examining your skin. However, since psoriasis can look like eczema and other skin diseases, diagnosing it can sometimes be difficult.
If your doctor isn't sure whether you have psoriasis, he or she may order a biopsy. Your doctor will remove a small sample of your skin and have it looked at under a microscope.
The signs and symptoms of psoriasis vary depending on the type you have. Some common signs for plaque psoriasis -- the most common type of psoriasis -- include:
Plaques of red, inflamed skin, often covered with loose, silver-colored scales. These plaques may be itchy and painful and sometimes crack and bleed. In severe cases, the plaques will grow and merge into one another, covering large areas.
Disorders of the fingernails and toenails, including discoloration and pitting of the nails....
Bruce E. Strober, MD, PhD. associate director of Dermatopharmacology, Department of Dermatology, New York University School of Medicine; co-director of the Psoriasis and Psoriatic Arthritis Center; consultant for Amgen, Biogen, Genentech, Fujisawa, and 3-M. Jeffrey M. Weinberg, MD, director of the Clinical Research Center, St. Luke's-Roosevelt Hospital Center, New York City; assistant clinical professor of dermatology, Columbia University College of Physicians and Surgeons; consultant for Amgen and Genentech. National Institute of Arthritis and Musculoskeletal and Skin Diseases web site. American Academy of Dermatology web site. WebMD Medical Reference with Healthwise: "Psoriasis." American Academy of Dermatology, PsoriasisNet web site. National Psoriasis Foundation web site. Abel, E. "Dermatology III: Psoriaisis," ACP Medicine, April, 2005.