Endocrine Abstracts

A reninoma is a tumour of the afferent arteriolar juxtaglomerular cells that secretes the enzyme renin, leading to hyperactivation of the renin-angiotensin-aldosterone system. It is a cause of pathological secondary hyperaldosteronism that results in severe hypertension and hypokalaemia. Fewer than 200 cases have been described, seven of which were associated with pregnancy. We present the case of a 29-year-old woman referred with hypertension and hypokalaemia at 10 weeks’ gestation of a dichorionic twin pregnancy. She was treated with Labetolol 600 mg four times daily, Methyldopa 1g three times daily and Nifedipine LA 60 mg twice daily to maintain a blood pressure of approximately 130/90mmHg. Her medical history included hypertension, diagnosed aged 19. She had one previous uncomplicated singleton pregnancy. There was no family history of hypertension or endocrinopathy. Recumbent plasma renin concentration was elevated at 67.7 ng/l (3-6 ng/l), and plasma aldosterone was elevated at 1425 pmol/l (<440 pmol/l). Tests for hypercortisolism and catecholamine excess were negative. Echocardiography revealed borderline concentric left ventricular hypertrophy and no coarctation of the aorta. Urine protein:creatinine ratio was elevated at 53.4 mg/mmol (<45 mg/mmol). A 2.4 cm solid, right renal lesion was identified on ultrasound. Further characterisation with magnetic resonance imaging demonstrated a heterogenous high signal area that indented the renal sinus fat and extended into the medullary area of the kidney. A biopsy of the lesion was arranged, and histopathology confirmed a juxtaglomerular cell tumour. No evidence of pre-eclampsia was seen. The patient proceeded for a right total nephrectomy at 16 weeks’ gestation. Macroscopically the lesion was a well circumscribed, haemorrhagic, tan-coloured mass lesion measuring 3.2×2.5×2.6 cm. The tumour was microscopically characterised by diffuse proliferation of tumour cells with moderate amounts of eosinophilic cytoplasm and vesicular nuclei. The tumour cells were positive for CD34, SMA, and vimentin and negative for CD117. Electron microscopy of the tumour showed rhomboid shaped granules characteristic of renin in tumour cells. The remainder of the kidney was unremarkable. The postoperative course was complicated by hypotension, and anti-hypertensive medications were discontinued. Supine plasma renin level measurement 7 weeks postoperatively was normal at 10.3 ng/l (<16 ng/l), 15% of the original value. Two infants were born via elective Caesarean section at 33+4 weeks gestation. Reninoma is a very rare and potentially curable form of hypertension, particularly in women of childbearing age. Plasma renin concentration was three times greater than the expected value for this stage of pregnancy. Management in pregnancy is challenging and involvement of the multi-disciplinary team is vital.