I know this dude who has mixed connective tissue disease. what is that?

Lupus/scleroderma: Mixed connective tissue disease (mctd) is an autoimmune disease that usually has features of lupus and scleroderma. Many people have raynaud's (fingers change color) and puffy fingers, and a positive ANA with a more specific test called "rnp" and may also have rashes, arthritis, or inflammation in other organs. It is treated a lot like lupus. Seeing a rheumatologist is helpful.