Nephrocalcinosis and renal cysts associated with apparent mineralocorticoid excess syndrome

Apparent mineralocorticoid excess (AME) syndrome is a rare inherited disorder caused by 11 beta -hydroxysteroid dehydrogenase (11-HSD 2) isozyme deficiency in the kidney. This enzyme is responsible for oxidizing cortisol to its inactive metabolite cortisone. An elevated tetrahydrocortisol (THF) and allotetrahydrocortisol (aTHF) to tetrahydrocortisone (THE) ratio in the urine is pathognomonic of AME syndrome. Clinical features include hypertension, hypokalemia, alkalosis, reduced plasma renin activity (PRA), low aldosterone levels, and occasionally nephrocalcinosis. Here we describe a 13-year-old boy who presented with severe hypertension, hypokalemia, low PRA and aldosterone levels, and elevated THF plus aTHF/THE ratio in the urine consistent with a diagnosis of AME syndrome. On ultrasound examination, he had severe nephrocalcinosis, and bilateral renal cysts. Renal cysts have not been previously reported in AME syndrome. The development of nephrocalcinosis and renal cysts may be associated with chronic long-standing hypokalemia. An early diagnosis and treatment of AME syndrome could help to prevent these sequelae, and to preserve renal function.