Psoriasis is a chronic immune-mediated disease that appears as thick, red patches of flaky, silver-white skin scales, and is the most common type of psoriasis. It occurs when the immune system speeds up skin cell growth cycles. The cause is not fully understood, but it may be due to either excessive skin cell growth or immune system factors producing skin cell growth. Symptoms include dry, scaling skin patches, nail changes, and potential joint pain. Diagnosis is usually based on skin appearance, and treatments include topical medications, systemic medications, and phototherapy.