Does psoriasis affect body parts other than the skin?

DEAR DOCTOR K: My doctor thinks my arthritis and heart disease are connected to my psoriasis. Is this possible? I thought psoriasis was a skin condition.
DEAR READER: Psoriasis (pronounced so-RYE-uh-sis) is named for an ancient Greek word meaning an itchy or scaly condition. It is classified as a skin disease, but psoriasis is the result of an immune system abnormality that can cause problems throughout the body.