Renal pseudohypoaldosteronism type 1

Renal pseudohypoaldosteronism type 1 (renal PHA1), also known as autosomal dominant pseudohypoaldosteronism type 1 or kidney-limited PHA1, is a rare inherited condition characterized by resistance to the hormone aldosterone specifically in the kidneys. Aldosterone normally acts on the kidneys to promote sodium reabsorption and potassium excretion. In renal PHA1, the kidneys do not respond properly to aldosterone, leading to excessive salt loss in the urine despite elevated aldosterone levels in the blood. This condition is caused by mutations in the NR3C2 gene, which encodes the mineralocorticoid receptor. The disease typically presents in the neonatal or early infantile period with salt-wasting episodes, including dehydration, poor feeding, failure to thrive, vomiting, and weight loss. Laboratory findings characteristically show hyponatremia (low blood sodium), hyperkalemia (high blood potassium), and metabolic acidosis, along with markedly elevated plasma renin and aldosterone levels. Unlike the more severe systemic (autosomal recessive) form of pseudohypoaldosteronism type 1, the renal form is limited to the kidneys and does not involve other organs such as the lungs, sweat glands, or colon. The prognosis for renal PHA1 is generally favorable. Treatment involves sodium chloride supplementation, which is particularly critical during infancy and early childhood when salt-wasting episodes can be life-threatening. The condition tends to improve with age, and many patients can reduce or discontinue sodium supplementation by later childhood or adulthood as the kidney's sensitivity to aldosterone gradually improves. Potassium-binding resins may occasionally be needed to manage hyperkalemia during acute episodes. Close monitoring of electrolytes is essential, especially during intercurrent illnesses that may precipitate salt-wasting crises.

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