Familial Hyperaldosteronism Type 1 Genetic Analysis

Diagnostic Use

Familial hyperaldosteronism type I (FH-I) is a rare heritable, glucocorticoid remediable form of primary aldosteronism (PA) characterized by early-onset hypertension, hyperaldosteronism, variable hypokalemia, low plasma renin activity (PRA), and abnormal production of 18-oxocortisol and 18-hydroxycortisol. PA is the most common form of secondary hypertension and is found in 10% of cases. However, familial forms are rare and represent 5% of adult PA cases. FH-I is estimated at 1% of all PA cases, but may attend 3% in the hypertensive pediatric population. Hypertension, of varying severity even among members of the same family, manifests often before the age of 20. It can be accompanied with symptoms of severe hypertension such as headaches and nausea. Cardiovascular anomalies, such as fibrosis, left ventricular (LV) dysfunction, arrhythmias, and myocardial infarction, can be associated with the disease. In adults, a high risk of cerebrovascular aneurysms is observed that causes premature hemorrhagic stroke.

FH-I is due to an unequal crossing over on the long arm of chromosome 8 between the CYP11B2 gene (coding for cytochrome P450 aldosterone synthase), normally expressed in the zona glomerulosa (ZG), and the CYP11B1 gene (coding for the 11 beta-hydroxylase), normally expressed in the zona fasciculata (ZF), resulting in a chimeric gene composed of the adrenocorticotropic hormone (ACTH)-sensitive promoter of the CYP11B1 gene and the coding region of the CYP11B2gene. This leads to an excessive aldosterone synthase production in the zona fasciculata of the adrenal gland, regulated by the hypothalamo-pituitary axis rather than by the renin-angiotensin system. Excessive aldosterone synthesis leads to increased sodium reabsorption, loss of potassium and subsequent increased water reabsorption.


Genetics - Molecular Pathology

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Constituent Tests



Turnaround Time

4 weeks

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