A renin-secreting tumor

Abstract

A 23-year-old white male was referred for hypertension resistant to triple antihypertensive treatment, with hypokalemia, hyperaldosteronism and elevated levels of circulating plasma renin activity (PRA). Renal angiography and echoscans put in evidence an avascular solid mass at the midlower level of the right kidney. Renal vein catheterization with sampling of blood from the lower branches of the right renal vein showed lateralization of renin secretion from that side. After surgical exeresis, the mass (1.0 cm) was diagnosed as a renal hemangiopericytoma on the basis of light and electron microscopy. Tumor exeresis was followed by a prompt normalization of blood pressure and plasma potassium, with a decrease in PRA and aldosterone. Two months after surgery the patient was still normotensive. Circulating levels of inactive (trypsin-activable) renin were around 60% of the total pool of plasma renin, i.e. much lower than those reported in other cases of renin-secreting tumors. After surgery, inactive and active renin fell in parallel, implying that both were secreted by the tumor. Tumoral PRA responded to postural stimulation, but was unresponsive to acute converting enzyme inhibition, suggesting that sympathetic stimuli were still operative, but the negative feedback inhibition by angiotensin II on renin secretion was lost. Acute converting enzyme inhibition by captopril dropped blood pressure; however, during long-term treatment, the drug (3 X 50 mg/day) was ineffective in terms of either blood pressure normalization or relief of secondary hyperaldosteronism. Acute calcium entry blockade by nifedipine (10 mg p.o.) caused an evident blood pressure drop.