Sjogren's is an autoimmune disorder. The symptoms associated with Sjogren's are caused by the infiltration of immune-system cells, usually B and T lymphocytes, into the glands responsible for secreting fluid. This particular autoimmune illness appears as inflammation in certain glands of the body that produce moisture such as the (lacrimal glands) that leads to decreased water production for tears and eye dryness and the salivary glands (including the parotid glands) that leads to mouth dryness.
Sjogren's syndrome that only involves gland inflammation (resulting dry eyes and mouth, etc.) and is not associated with a connective tissue disease is referred to as primary Sjogren's syndrome.
Secondary Sjogren's syndrome involves not only gland inflammation but is also associated with a connective tissue disease such as systemic lupus, rheumatoid arthritis erythematosus or scleroderma.