What are the differences between psoriatic arthritis and rheumatoid arthritis?

Hi. I’m no doctor but from what I’ve read, RA attacks joints in a symmetrical fashion, PA is more of a reactive arthritis and can effect multiple joints throughout the body. Plus PA can have accompanying psoriasis.

I thought I had RA, but when doctor saw my swollen toe she asked if I had any dry scalp issues. I told her just this spot on the back of my head that gets a little itchy sometimes. After looking at it she said, this isn't RA, it's PsA. Apparently RA does not affect the toes.