'Treasure your exceptions': what we can learn from autosomal-dominant inherited forms of hypertension.

OBJECTIVE

To discuss the relevance of rare monogenic forms of hypertension to the diagnosis, pathogenesis and treatment of essential hypertension.

STUDY SELECTION

Three monogenic forms of hypertension have been identified that are inherited as a simple autosomal-dominant trait. The genetic defects and the pathophysiology of two, namely glucocorticoid-remediable aldosteronism and Liddle's syndrome, have been elucidated in great detail. The third form of monogenic hypertension, which cosegregates with a second phenotype, brachydactyly, is being investigated.

RESULTS

Glucocorticoid-remediable aldosteronism is caused by the presence of a chimeric gene, which incorporates the regulatory region of the 11-beta-hydroxylase gene and the structural portion of the aldosterone synthase gene. The enzyme aldosterone synthase is not only expressed in the zona fasiculata but is also regulated by adrenocorticotrophic hormone in this condition. Liddle's syndrome is caused by mutations in the beta subunit of the epithelial sodium channel. The mutations result in inappropriate channel patency and increased distal sodium reabsorption. Both of these forms of inherited hypertension are low-renin forms of hypertension. Glucocorticoid-remediable aldosteronism resembles primary aldosteronism, whereas Liddle's syndrome resembles low-renin essential hypertension. An autosomal-dominant genetic form of hypertension has been described in northeastern Turkey. The hypertension cosegregates 100% with brachydactyly. This form resembles essential hypertension, because levels of renin, aldosterone, catecholamines and other regulators are normal. Furthermore, in contrast to glucocorticoid-remediable aldosteronism and Liddle's syndrome, the patients are not salt-sensitive.

CONCLUSIONS

Mechanisms of mineralcorticoid hypertension, renally induced salt-sensitive hypertension, and possibly essential hypertension, may be elucidated by studying exceptional families.