Pseudohypoaldosteronism type 1 (PHA1) is a condition characterized by problems regulating the amount of sodium in the body. Sodium regulation, which is important for blood pressure and fluid balance, primarily occurs in the kidneys. However, sodium can also be removed from the body through other tissues, such as the sweat glands and colon. Pseudohypoaldosteronism type 1 is named for its characteristic signs and symptoms, which mimic (pseudo) low levels (hypo) of a hormone called aldosterone that helps regulate sodium levels. However, people with PHA1 have high levels of aldosterone.

Mutations in one of four different genes involved in sodium regulation cause autosomal dominant or autosomal recessive PHA1. Mutations in the NR3C2 gene cause autosomal dominant PHA1. This gene provides instructions for making the mineralocorticoid receptor protein. Mutations in the SCNN1A, SCNN1B, or SCNN1G genes cause autosomal recessive PHA1. Each of these three genes provides instructions for making one of the pieces (subunits) of a protein complex called the epithelial sodium channel (ENaC).

PHA1 is a rare condition that has been estimated to affect 1 in 80,000 newborns.

PHA1 can have different inheritance patterns. When the condition is caused by mutations in the NR3C2 gene, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. When PHA1 is caused by mutations in the SCNN1A, SCNN1B, or SCNN1G genes, it is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Published Date: December 01, 2011
Published By: National Institutes of Health