Pseudohypoaldosteronism (PHA) is a rare syndrome of mineralocorticoid resistance. PHA type 1 (PHA1) can be divided into two different forms, showing either a systemic or a renal form of mineralocorticoid resistance. The first is caused by mutations of the genes coding the epithelial sodium channel, the latter is caused by mutations in the mineralocorticoid receptor coding gene NR3C2. The clinical manifestation of systemic PHA1 is overt dehydration and hyponatremia due to systemic salt loss and severe hyperkalemia. The leading clinical sign of the less severe renal PHA1 is insufficient weight gain due to chronic dehydration. Hyperkalemia is generally mild. The patients manifest clinical signs mainly in early infancy. In both entities, plasma renin and aldosterone concentrations are highly elevated, reflecting a resistance of the kidney and other tissues to mineralocorticoids. PHA2 is characterized by hyperkalemia and hypertension. It has been described by Gordon's group as a syndrome with highly variable plasma aldosterone concentrations, suppressed plasma renin activity, various degrees of hyperchloremia and metabolic acidosis. PHA3 comprises transient and secondary forms of salt-losing states caused by various pathologies. Urinary tract infections and obstructive uropathies are the most frequent cause. Contrary to PHA1 and PHA2, the glomerular filtration rate is decreased in PHA3.
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