Final answer:
Sjögren's syndrome is likely due to autoimmune issues, such as genetic factors or environmental triggers, though the exact cause remains unclear.
Step-by-step explanation:
The patient's history of Sjögren's syndrome is most likely due to an autoimmune disorder, where the body's immune system mistakenly attacks its own tissues. Sjögren's syndrome is characterized by symptoms such as dry eyes and dry mouth, as the immune system primarily targets the glands that produce saliva and tears. Factors that may have contributed to developing Sjögren's syndrome can include genetic predisposition, viral or bacterial infection, hormonal changes, and environmental triggers, although the exact cause is still not fully understood.