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, they may order a biopsy. Your doctor will remove a small sample of your skin and have it looked at under a microscope.
If you have symptoms of psoriatic arthritis, such as swollen and painful joints, your doctor might run blood tests and take X-rays to rule out other forms of arthritis.