Juxtaglomerular Cell Tumor: Multicentric Synchronous Disease Associated With Paraneoplastic Syndrome

Case ReportA 50-year-old white man presented to the emergency department for a hypertensive crisis that was causing headache and nausea.Blood pressure was 200/120 mmHg, the physical examination was unremarkable, whereas blood tests showed sodium levels of 116 mmol/L and potassium levels of 3.2 mmol/L.Past medical history included a myocardial infarction 10 years before, ischemic heart disease, diabetes, and arterial hypertension, which was poorly controlled by a calcium-channel blocker and an angiotensin-converting enzyme inhibitor.In the previous months, the patient had begun to suffer from abdominal pain, dyspepsia, and vomiting that had resulted in weight loss of 16 kg in 7 months.Gastroscopy and colonoscopy were negative, whereas an abdominal ultrasound revealed the presence of a splenic cyst that measured 4.5 cm in maximum diameter.The patient was admitted to the nephrology department for diagnosis and determination of a therapeutic approach.Laboratory values confirmed hypotonic euvolemic hyponatremia; levels of thryroid-stimulating hormone, cortisol, and adrenocorticotropic hormone were in the normal ranges, whereas urinary sodium was strongly elevated (111 mmol/L).Water restriction and hypertonic administration failed to raise sodium levels, thus ruling out primary polydipsia.Coexistence of hypotonic hyponatremia, without signs of depletion or expansion of blood volume or of hormonal imbalances, was consistent with diagnosis of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH; Table 1).Pharmacologic causes of SIADH were ruled out, and we turned our attention toward locating a neoplasm responsible for the syndrome, considering the history of weight loss and abdominal pain.The patient underwent a thoraco-abdominal computed tomography (CT) scan that revealed the presence of a splenic mass D I A G N O S I S I N O N C O L O G