A Pediatric Case of Reninoma Presenting with Paraneoplastic SIADH.

INTRODUCTION: A reninoma (juxtaglomerular cell tumour) is a rare cause of secondary hypertension that can present with headaches alongside the triad of severe hypertension, hypokalemia, and metabolic alkalosis.

CASE PRESENTATION: We describe a case of a 15-year-old previously healthy girl who presented with headaches and hypertensive urgency who had severe hypokalemia, moderate hyponatremia and elevated aldosterone and renin levels. Abdominal ultrasound and MRI with contrast revealed a unilateral mass localized to the right kidney. Despite treatment of her hypertension, she had persistent hyponatremia with clinical euvolemia which was consistent with the paraneoplastic syndrome of inappropriate antidiuretic hormone secretion (SIADH). She underwent radical nephrectomy which normalized her blood pressure and aldosterone and renin values. The pathology findings were consistent with a reninoma with a mitotic rate of 1-2 mitoses per 10 high power fields.

DISCUSSION/CONCLUSION: Hypertension in the pediatric age group requires work-up to rule out secondary causes. The classic triad of hypertension, hypokalemia, and metabolic alkalosis warrants assessment for aldosterone-mediated hypertension which can be a result of a renin-producing tumour. Curative approach requires surgical resection of the tumour. Reninomas may rarely manifest with a paraneoplastic phenomenon including SIADH, as seen in our case. Although reninomas are benign tumours, there are also a few reports of malignant transformation and metastases. Features uncommon in reninomas such as mitotic activity warrant long-term surveillance.