Getting an Accurate Diagnosis

The road to a diagnosis of Familial Hyperaldosteronism Type IV (FH4) often begins with a routine blood pressure check that shows unexpectedly high numbers for a child. Because FH4 is so rare, the diagnostic process follows a specific sequence of steps designed to first prove that the body is making too much aldosterone, and then to find the genetic reason why.

CRITICAL WARNING: Never stop, start, or change the dose of any blood pressure medication or potassium supplement on your own to “prepare” for a test. This can be extremely dangerous. Medication changes must be strictly supervised by a specialist.

The First Step: The Screening Ratio

The most important screening tool is a blood test called the Aldosterone-to-Renin Ratio (ARR) ^[1].

• Aldosterone is the hormone that raises blood pressure ^[2].
• Renin is a protein that the kidneys release to signal the body to make aldosterone.

In a healthy person, if aldosterone is high, renin should be low to balance it out. In FH4, the adrenal glands ignore the body’s signals. Doctors look for a “biochemical triad”: high absolute aldosterone, very low or “suppressed” renin, and a high ratio between the two ^[3][4].

Important Considerations for the ARR Test:

• Assays and Units: The ARR result highly depends on the specific laboratory assay, units used, and age-specific pediatric reference ranges. A suppressed renin alone is not diagnostic.
• Potassium Matters: If your child’s potassium is low at the time of the test, it can actually “hide” the problem by lowering aldosterone levels, leading to a false-normal result ^[5]. Potassium should be corrected by your doctor before the blood draw ^[6].
• Medication Interference: Many common blood pressure medications (like ACE inhibitors, beta-blockers, or diuretics) can change renin and aldosterone levels ^[7]. Your doctor may need to temporarily switch your child to “cleaner” medications under close supervision to get an accurate reading ^[1].
• Normal Potassium is Not a Rule-Out: You can have a perfectly normal potassium level and still have FH4. If blood pressure is high and early-onset, the ARR test is usually still recommended ^[5].

Confirmatory Testing

If the ARR is high, doctors may perform a confirmatory test to see if the body can “shut off” aldosterone production when given a salt load. Common methods include the saline infusion test (giving salt water through an IV) or the captopril challenge ^[8][9].

In some cases, if the results are very clear—such as very low potassium and extremely high aldosterone—doctors may skip these steps and move straight to genetic testing to avoid unnecessary procedures for the child. Furthermore, these tests have limited pediatric validation and can be unsafe in children with severe hypertension or volume concerns, making them individualized specialist tests ^[4][10].

Why Adrenal Scans are Misleading

One of the most confusing parts of the FH4 journey is that standard imaging, like CT scans or MRIs, often comes back “normal” or shows “minor bumps” ^[11].

In common adult forms of this disease, there is often a single, large tumor (an adenoma) that shows up clearly on a scan. However, FH4 is a systemic genetic channelopathy, meaning every cell in both adrenal glands has the altered calcium channel ^[11].

• The glands may look completely healthy on a scan even while they are overproducing hormones ^[12].
• Small, harmless nodules (incidentalomas) are common and can trick doctors into thinking surgery is needed on a gland that isn’t the primary problem ^[13].

For these reasons, imaging alone is never enough to diagnose or rule out FH4.

The Definitive Genetic Test

The test for confirming the FH4 subtype is a germline genetic test, typically using a Next-Generation Sequencing (NGS) panel ^[11][14]. This test looks specifically for a variant in the CACNA1H gene.

• Pathogenic vs VUS: A pathogenic or likely pathogenic variant confirms the genetic etiology. A Variant of Uncertain Significance (VUS) does not establish the diagnosis and should not drive family testing.
• Limitations: A negative panel does not necessarily exclude primary aldosteronism.

Confirming the pathogenic CACNA1H variant is vital because it guides the specialist’s treatment plan, emphasizing medical management, and provides crucial information for genetic counseling and testing relatives ^[11].