Sialadenosis, also referred to as sialosis, is a disease of unknown aetiology. It regularly manifests itself as a massive swelling in both parotid regions involving the major salivary glands, preferably the parotid glands and is characterized by lack of any detectable, underlying pathologies. In this case report we describe a 24-year-old white female patient with diabetes insipidus who developed sialadenosis of the major salivary glands during a period of enhanced water requirement, which the patient tried to compensate for by more frequent nasal ADH application. Since ADH acts on aquaporins (AQPs) in the kidney, we were interested if AQP expression in the patients salivary glands was affected. Surprisingly, compared to normal control tissues we observed an extensively high signal for AQP5, which is the dominant AQP found in salivary acinar cells. Interestingly, previous studies on AQP5 knock out mice found AQP5 to be required for cell volume regulation. We therefore suggest that aquaporin water channels and antidiuretic hormone together with a disturbance in the body's water household are potential key-factors in the pathophysiological events leading to the development of the disease entity called sialadenosis.