Autosomal dominant Pseudohypoaldosteronism Type I (adPHA1) is caused by mutations to the mineralocorticoid receptor (MR) that cause it to be unresponsive to aldosterone.
Inheritance: autosomal dominant
Gene Map Locus: 4q31.1
Gene affected: mineralocorticoid receptor
Clinical features:
(1) renal salt-wasting starting at birth
(2) volume depletion
(3) failure to thrive
(4) short stature
(5) vomiting
(6) clinical improvement with a high salt diet
(7) decrease in symptoms and the need for a high salt after early childhood
(8) may require therapy with potassium binding resins during infancy and early childhood
Laboratory findings:
(1) hyponatremia
(2) hyperkalemia
(3) metabolic acidosis
(4) high normal to elevated plasma levels of aldosterone
(5) normal sodium levels in sweat and saliva
Possible explanations for change in sodium handling with age:
(1) up-regulation of aldosterone synthesis
(2) postnatal development of the potassium secretory channel (ROMK) in the renal tubule
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