Overlap syndrome is having sympotoms of two or more autoimmune diseases without having the diseases.
You can have several symptoms of lupus (SLE) like inabliity to tolerate bright light or loud noise, and irregular menstral cycles, chest pains, lesions.
Sjogren's Syndrome having dry eyes, dry mouth, tooth loss, difficulty swallowing dry foods like cake or toast.
Raynauds Phenomenon is inablilty to tolerate cold, Feet, hands, toes fingers turn white to the touch, imediate pain when exposed to cold.
These are only a few of the diseases and symptoms, there are so many more.
I was told by my Internist, if you do fully have these diseases they are called 'piggy-backed'.
He also tells me that chances are once you have an overlap diagnosis that you will in time have the full disease, a complete diagnosis.
This can also be called 'Fibromyalgia Syndrome', as a 'trash diagnosis'.
There is conflict as to how different Physicians or reference material define these conditions, syndromes, or diseases, but this is how it was explained to me. I do not claim to be a medical professional or post these as a means of self diagnosis.
Keep an on-going list of your symptoms, take them to your Doctor, know your family history. Do research! Go to a Rheumatologist or Fibro specialist, if you are not satisfied with your treatment, go to another Doctor. Don't give up!