What you are describing can be attributed to several different root causes. One of them is a fungal infection. What you described mimics how it started in one of my hamsters. It was a small thinning patch of hair on his right shoulder (closer to his back). If we looked closely at the thinning hair, we could see very small white specks on his skin (that did not come off). We made several visits to the vet (different vets!) to get a diagnosis. In a matter of months it evolved to what you see in these pictures on our web site:
https://sites.google.com/site/ourrobohamsters/
My advice is to find a good exotic mammal vet (we can help you do so if you ask). The treatment is simple and effective, but it is important to get a diagnosis first. If you take your Syrian in to the vet and the vet says, "It looks like it could be mites, let’s start with this", then turn around and get a different vet
. The vet needs to do the proper tests to come to a diagnosis (fungal cultures, skin scrapes, etc.).
I hope this helps!