http://www.sjogrens-guidebook.com/2009/landinge.php?gid=RH011&?a=a&assoc=Google&keyword=Sjogrens
This looks like and interesting read, is recently updated and includes treatment centers.
It lists the underlying causes of Sjogren's as:
Chronic Inflammation
Cellular Apoptosis (death of a cell)
Autonomic Nervous system dysfunction
Neurotransmitter abnormality
Genetic predisposition