I was told that i either have sle or mixed connective tissue disease (i already have a rheumatology appt) i was just wondering what's the difference?

Let me explain: Mixed connective tissue disease features signs and symptoms of a combination of disorders — primarily of lupus, scleroderma and polymyositis. For this reason, mixed connective tissue disease is sometimes referred to as an overlap disease.

Overlap of signs: Sle (lupus) and mixed connective disease have overlap of some symptoms and signs. When there aren't enough diagnostic criteria to conclude lupus, but some characteristic findings of connective tissue disease, they call it mixed. Lupus has 11 possible categories of labs or physical findings according to the acr.

Very different: Mixed connective tissue disease is a specific disease characterized by a combo of symptoms with a high titer rnp antibody. Lupus is the prototype connective tissue disease. Undifferentiated connective tissue disease is usually lupus-like but doesn't meet criteria for lupus.