A 42-year-old female seeks medical attention complaining of mouth dryness. Denies xerophthalmia, arthralgia, stiffness or joint swelling. Denies dermatological complaints or use of tricyclic antidepressants. In physical examination, it was noted dryness of the labial mucosa and atrophic and dry tongue, no other abnormalities. Laboratory exams showed positive ANA and anti-Ro/SS-A antibodies, only. Requested salivary glands scintigraphy.
A 42-year-old female seeks medical attention complaining of mouth dryness. Denies xerophthalmia, arthralgia, stiffness or joint swelling. Denies dermatological complaints or use of tricyclic antidepressants. In physical examination, it was noted dryness of the labial mucosa and atrophic and dry tongue, no other abnormalities. Laboratory exams showed positive ANA and anti-Ro/SS-A antibodies, only. Requested salivary glands scintigraphy. 
Image 2: (A) Regions of interest (ROI) delimiting the glands. (B) Radioactive curves of activity X minutes before and after the administration of a small amount of acid substance (lemon juice).
Question:
In light of the patient’s clinical condition and of the scintigraphy image above, what is the main diagnostic hypothesis?
