A chimeric CYP11B1/CYP11B2 gene in glucocorticoid-insuppressible familial hyperaldosteronism

Although a chimeric gene combining the 11 beta -hydroxylase gene (CYP11B1) and the aldosterone synthase gene (CYP11B2) explains the pathophysiology of familial hyperaldosteronism (FH) type I, the contribution of this abnormal ity to FH type II has not been tested. We screened genomic DNA from a Japan ese family with FH type II for the CYP11B1/CYP11B2 gene. The index patient was a 27-year-old woman with hypertension. Hypokalaemia, elevated plasma al dosterone and suppressed plasma renin activity suggested primary aldosteron ism. Though computed tomography failed to reveal an adrenal tumour, left ad renalectomy was indicated due to a high aldosterone concentration in left a drenal venous blood. The resected adrenal gland contained an adenoma. As he r mother had also been diagnosed with primary aldosteronism due to an adeno ma, we administered oral dexamethasone to our patient before the operation and observed the response of the blood pressure and plasma aldosterone conc entration for 2 weeks. Both parameters remained elevated during the treatme nt period, confirming the diagnosis of FH type II. Total DNA was isolated f rom blood cells of the index patient, her mother, and an unaffected brother . Samples were amplified by polymerase chain reaction using specific primer s from CYP11B1 and CYP11B2. Unique DNA fragments of 1.4 kb were obtained fr om the index patient and her mother, but not from the healthy subject. The CYP11B1/CYP11B2 chimeric gene was found in a Japanese family with FH type I I.