A 60–year–old female bookkeeper with a past medical history significant for a 40 pack year smoking history presented to her primary care physician with a complaint of a persistent sweet taste in her mouth. The dysgeusia (dysfunction in taste) started about two months prior to presentation and had progressively gotten worse. She reported the sweet taste was continuous throughout the day. On physical exam her blood pressure was 152/84 mm Hg and her heart rate was 66. She was euvolemic in appearance. Respiratory exam revealed diffuse inspiratory and expiratory wheezes. Serum chemistries revealed significant hyponatremia with a sodium concentration of 110 mmol/L. The remaining renal function, electrolytes, and CBC were normal including a plasma glucose of 114 mg/dl. Her serum osmolality was 230 mmol/kg. Chest X–ray revealed increased mediastinal width and further imaging with CT scan revealed two pulmonary masses in the right upper lobe and hepatic metastases. With the imaging results and her serum hypo–osmolality it was concluded her severe hyponatremia was caused from Syndrome of Inappropriate Antidiuretic Hormone (SIADH). Pathology evaluation of her pulmonary mass biopsy revealed extensive small cell lung cancer with metastatic disease. The hyponatremia was initially treated with fluid restriction and conivaptan infusion. As her serum sodium concentration gradually corrected to 129 mmol/L, the sweet taste in her mouth began to resolve and finally subsided.
SIADH secondary to Lung Cancer most commonly presents with symptoms related to the cellular swelling and cerebral edema associated with hyponatremia. The symptoms usually include lethargy, disorientation, agitation, headaches, blurry vision and nausea. In this case, we report a highly unusual presentation of SIADH: dysgeusia, which led to the diagnosis of small cell lung cancer. It is likely that the hyponatremia was the cause of the dysgeusia rather than the malignant tumors or the SIADH as the sweet taste resolved as the hyponatremia was corrected. Dysgeusia is often present in patients with malignancy that are being treated. Although persistent sweet taste, has rarely been reported as a presenting symptom of hyponatremia.
Usually when a patient presents with a sweet taste in their mouth, the first thought is of diabetes leading to a check of serum glucose levels. A patient presentation of persistent dysgeusia not related to glucose levels should now lead to a larger evaluation. This should prompt an evaluation of the serum sodium concentration and then further evaluation for the possibility of malignancy in patients with dysgeusia.