Army Medical Service (Germany)

Apparent Mineralocorticoid Excess Syndrome

Apparent Mineralocorticoid Excess Syndrome (AME) is a rare genetic disorder characterized by hypertension, hypokalemia, metabolic alkalosis, and low plasma renin activity. It is caused by mutations in the gene encoding the enzyme 11_-hydroxysteroid dehydrogenase type 2 (11_-HSD2), which is responsible for converting active cortisol to its inactive form, cortisone.

Pathophysiology

The 11_-hydroxysteroid dehydrogenase type 2 enzyme plays a crucial role in protecting the mineralocorticoid receptor from activation by cortisol. In individuals with AME, the deficiency or dysfunction of this enzyme leads to an accumulation of cortisol, which can bind to and activate the mineralocorticoid receptor. This results in effects similar to those of excessive aldosterone, despite normal or low levels of aldosterone in the body.

Genetics

AME is inherited in an autosomal recessive manner. This means that an individual must inherit two copies of the mutated gene, one from each parent, to manifest the disorder. The gene responsible for AME is located on chromosome 16 and is known as HSD11B2.

Clinical Features

Patients with AME typically present with:

• Severe hypertension
• Hypokalemia (low potassium levels)
• Metabolic alkalosis
• Low plasma renin activity
• Normal or low levels of aldosterone

Diagnosis

The diagnosis of AME is based on clinical features, biochemical tests, and genetic testing. Biochemical tests reveal low renin and aldosterone levels, along with hypokalemia and metabolic alkalosis. Genetic testing can confirm mutations in the HSD11B2 gene.

Treatment

Treatment of AME focuses on managing hypertension and correcting electrolyte imbalances. Medications such as spironolactone or eplerenone, which are mineralocorticoid receptor antagonists, can be used to block the effects of cortisol on the mineralocorticoid receptor. Dietary modifications, such as reducing sodium intake and increasing potassium intake, may also be beneficial.

Related Pages

• Hypertension
• Hypokalemia
• Metabolic alkalosis
• Aldosterone

Gallery

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  Inheritance pattern of autosomal recessive disorders

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  Army Medical Service (Germany)