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Pseudohypoaldosteronism Type I

by James I. McMillan, MD

Pseudohypoaldosteronism type I is a group of rare hereditary disorders that cause the kidneys to retain too much K but excrete too much Na and water, leading to hypotension. Symptoms may result from hypotension, hypovolemia, hyponatremia, and hyperkalemia. Treatment is with a high Na diet and sometimes fludrocortisone or carbenoxolone.

Inheritance is autosomal recessive or autosomal dominant. Infants with autosomal recessive pseudohypoaldosteronism type I are resistant to the effects of aldosterone due to mutations causing decreased activity of the epithelial Na channels (ENaC) located on the luminal membrane (overactivity of ENaC causes K excretion and Na retention—see Liddle Syndrome). The autosomal recessive form tends to be severe and permanent. The Na channel in tissues other than the kidneys may be affected, leading to a miliary rash and/or complications similar to those of cystic fibrosis (see Cystic Fibrosis).

Children with autosomal dominant pseudohypoaldosteronism type 1 are resistant to mineralocorticoids due to mutations of the mineralocorticoid receptor. The autosomal dominant form is usually less severe, affecting mainly the mineralocorticoid receptor in the kidney, and may resolve somewhat as children age.

Pseudohypoaldosteronism type I resembles other forms of hypoaldosteronism except that aldosterone levels are high. The very rare pseudohypoaldosteronism type II is not discussed here.

Diagnosis

  • Plasma renin and aldosterone levels

The diagnosis is suspected based on clinical findings of hypovolemia, high serum K, low serum Na, high renin and aldosterone levels, particularly in infants with a positive family history. The diagnosis is confirmed by genetic testing.

Treatment

  • High Na diet and sometimes fludrocortisone or carbenoxolone

A high Na diet helps maintain volume and BP and increases excretion of K. If ineffective, fludrocortisone (0.5 to 1.0 mg po bid or 1 to 2 mg po once/day) or carbenoxolone can be given.

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