SCNN1B Gene

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.

There are two types of PHA1 distinguished by their severity, the genes involved, and how they are inherited. One type, called autosomal dominant PHA1 (also known as renal PHA1) is characterized by excessive sodium loss from the kidneys. This form of the condition is relatively mild and often improves in early childhood. The other type, called autosomal recessive PHA1 (also known as generalized or systemic PHA1) is characterized by sodium loss from the kidneys and other organs, including the sweat glands, salivary glands, and colon. This type of PHA1 is more severe and does not improve with age.

The earliest signs of both types of PHA1 are usually the inability to gain weight and grow at the expected rate (failure to thrive) and dehydration, which are typically seen in infants. The characteristic features of both types of PHA1 are excessive amounts of sodium released in the urine (salt wasting), which leads to low levels of sodium in the blood (hyponatremia), and high levels of potassium in the blood (hyperkalemia). Infants with PHA1 can also have high levels of acid in the blood (metabolic acidosis). Hyponatremia, hyperkalemia, or metabolic acidosis can cause nonspecific symptoms such as nausea, vomiting, extreme tiredness (fatigue), and muscle weakness in infants with PHA1.

Infants with autosomal recessive PHA1 can have additional signs and symptoms due to the involvement of multiple organs. Affected individuals may experience episodes of abnormal heartbeat (cardiac arrhythmia) or shock because of the imbalance of salts in the body. They may also have recurrent lung infections or lesions on the skin. Although adults with autosomal recessive PHA1 can have repeated episodes of salt wasting, they do not usually have other signs and symptoms of the condition.