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Pseudohypoaldosteronism Type I

By James I. McMillan, MD

Pseudohypoaldosteronism type I is a rare hereditary disorder in which the kidney tubules retain too much potassium and excrete too much sodium and water, leading to low blood pressure.

There are two types of pseudohypoaldosteronism

  • Type I, which has 2 subtypes and is characterized by low blood pressure

  • Type II, which is very rare (not discussed here)

Two different gene mutations can cause pseudohypoaldosteronism type I. In both, the body does not respond to the hormone aldosterone , leading to the excretion of too much sodium and water. However, the two types differ. In one type excess sodium is excreted only by the kidneys. In the other, more severe form, excess salt is also lost through sweat and from other organs.

Children with the severe form may have symptoms similar to those of cystic fibrosis, such as frequent respiratory tract infections. They may have

  • Dehydration, possibly causing nausea and vomiting

  • Fatigue

  • Muscle weakness

  • Low blood pressure, sometimes with dizziness and fainting

Sodium loss through sweat may cause a rash of very small red bumps.

The less severe form may cause few symptoms other than those of low blood pressure. In the less severe form, the disorder may resolve as children age.

Diagnosis

  • Blood pressure measurement

  • Blood and urine tests

In addition to measuring blood pressure, doctors measure the amount of sodium and potassium in the urine and blood. They may also do blood tests to detect levels of hormones that help regulate sodium levels in the blood and thus blood pressure (renin and aldosterone ).

Genetic testing may also be done.

Treatment

  • Eating a high-salt diet

Treatment is eating a diet that is high in salt (salt contains sodium). Sometimes people need to take fludrocortisone, a drug that helps the kidneys retain sodium and water.

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