Understanding Familial Hyperaldosteronism Type IV (FH4)

Finding out that you or your child has Familial Hyperaldosteronism Type IV (FH4) can feel overwhelming, especially after a long and confusing journey to get a name for their symptoms. Because this condition is exceptionally rare, many families spend years searching for answers while managing unexplained high blood pressure or low potassium ^[1]. It is completely normal to feel a mix of relief at finally having a diagnosis and anxiety about what it means for the future. You are not alone in this; though the condition is rare, there is a clear biological reason for what your child is experiencing.

What is Familial Hyperaldosteronism Type IV?

Familial Hyperaldosteronism Type IV is a genetic form of primary aldosteronism, a condition where the adrenal glands (small glands sitting on top of the kidneys) produce too much of a hormone called aldosterone ^[2].

Normally, the body uses aldosterone to balance salt and potassium to keep blood pressure stable. In FH4, the regulation of this hormone is disrupted. This leads to:

• High blood pressure (hypertension), often starting in early childhood (typically before age 10) ^[3].
• Low potassium (hypokalemia), which can cause muscle weakness or fatigue, though some children may have normal potassium levels ^[1][4].
• Suppressed renin, a protein that normally helps regulate blood pressure but gets “turned off” when aldosterone is too high ^[5].

The Genetic Cause: The CACNA1H Gene

FH4 is caused by a pathogenic or likely pathogenic germline variant (a change in the DNA present from birth) in the CACNA1H gene ^[2]. This gene provides the instructions for making a specific doorway into cells called the CaV3.2 T-type calcium channel ^[6].

In a healthy adrenal gland, calcium moves through these channels to signal the gland to make aldosterone only when the body needs it. In FH4, the variant alters these channels. They allow calcium to enter the adrenal cells excessively ^[7]. This excessive calcium signal causes the gland to produce an inappropriately regulated supply of aldosterone ^[6][2].

What a genetic result means: A pathogenic or likely pathogenic variant confirms the diagnosis. A Variant of Uncertain Significance (VUS) does not establish FH4 and should not be used to test relatives. A negative panel does not exclude primary aldosteronism.

How Rare is FH4?

FH4 is one of the rarest forms of primary aldosteronism. While primary aldosteronism itself is common in adults with high blood pressure, the familial (inherited) forms are much less frequent.

• Overall Rarity: Some registries suggest familial forms make up less than 1% to 4% of all primary aldosteronism cases ^[8].
• Documented Cases: Only a small number of families worldwide have been formally diagnosed with FH4 since its discovery ^[1].
• Variable Expression: Even within the same family, the condition can look different. One person might have severe high blood pressure as a child, while another relative with the same variant might be asymptomatic or have milder symptoms ^[1][9].

Distinguishing FH4 from Other Types

It is important to understand how FH4 differs from more common forms of the disease.

Next Steps in Your Journey

Because FH4 is a lifelong genetic condition, management focuses on protecting the heart and kidneys by keeping blood pressure and hormone levels in a healthy range.

• Genetic Testing: A definitive diagnosis requires a specialized blood test (often a multigene panel) to confirm the pathogenic CACNA1H variant ^[10].
• Family Screening: Because this is an inherited condition, doctors often recommend cascade screening, which means testing other family members for the established pathogenic variant ^[1].
• Medication: The mainstays of treatment are mineralocorticoid receptor antagonists (MRAs) like spironolactone or eplerenone ^[5]. These drugs block the effects of the extra aldosterone.
• Monitoring: Your care team will watch your child’s blood pressure, potassium levels, and renin levels. Renin is one marker used by specialists to verify the medication is successfully blocking the excess aldosterone ^[5].