When is genetic testing indicated for primary aldosteronism and which adrenal-specific genes should be evaluated?

Genetic Testing for Primary Aldosteronism

Genetic testing should be performed in all patients with primary aldosteronism diagnosed before age 20 years, all first-degree relatives of patients with familial hyperaldosteronism, and any patient with a family history of early-onset PA or stroke before age 40 years 1, 2.

When to Order Genetic Testing

The 2025 Endocrine Society guidelines and French consensus establish clear criteria for genetic screening 1, 2:

Mandatory Testing Scenarios:

• Age <20 years with confirmed PA - regardless of potassium levels or family history
• First-degree relatives of confirmed familial hyperaldosteronism cases - even before hypertension develops, as cardiac damage can precede blood pressure elevation 2
• Family history of PA at any age in the patient or relatives
• Family history of stroke before age 40 years 2
• Resistant hypertension with severe hypokalemia before age 20 2

Key Clinical Pitfall:

Do not wait for overt hypertension to screen family members. Aldosterone-mediated cardiac effects can occur before blood pressure rises, making early identification critical for preventing irreversible damage 2.

Which Genes to Test

The genetic evaluation should target specific familial hyperaldosteronism subtypes based on clinical presentation:

Familial Hyperaldosteronism Type I (FH-I)

• Gene: Chimeric CYP11B1/CYP11B2 fusion gene
• Testing method: Long-range PCR or Southern blot 2
• Clinical features: Glucocorticoid-remediable aldosteronism; responds to dexamethasone suppression
• Strong recommendation for this testing in all patients meeting age/family history criteria 2

Familial Hyperaldosteronism Type III (FH-III)

• Gene: KCNJ5 (codes for GIRK4 potassium channel)
• Clinical features: Severe early-onset hypertension in childhood with profound hypokalemia, resistant to treatment 2, 3
• Severity varies by mutation: p.Gly151Arg, p.Thr158Ala, p.Ile157Ser, and p.Glu145Gln cause severe phenotypes requiring bilateral adrenalectomy; p.Gly151Glu and p.Tyr152Cys cause moderate disease 2
• Elevated urinary 18-hydroxycortisol and 18-oxocortisol; not suppressed by dexamethasone 2

Additional Genes in Familial Forms

Based on recent genetic discoveries, germline mutations have been identified in 3, 4:

• CACNA1D (calcium channel CaV1.3) - FH-IV
• CACNA1H (calcium channel CaV3.2)
• CLCN2 (chloride channel ClC-2)

Somatic Mutations (Not for Routine Clinical Testing)

While somatic mutations in KCNJ5, CACNA1D, ATP1A1, ATP2B3, CACNA1H, CLCN2, CTNNB1, and GNAQ/11 are found in >90% of aldosterone-producing adenomas 3, these are not currently recommended for routine clinical genetic screening as they don't change management 2. However, this landscape may evolve as targeted therapies develop.

Algorithmic Approach to Genetic Testing

Step 1: Identify high-risk patients using age and family history criteria above

Step 2: For patients <20 years OR with family history of early PA/stroke:

• Order FH-I testing (CYP11B1/CYP11B2 chimeric gene) first 2

Step 3: If FH-I negative AND severe childhood-onset resistant hypertension with hypokalemia:

• Order FH-III testing (KCNJ5 germline mutations) 2

Step 4: If both negative and strong clinical suspicion persists:

• Consider expanded panel including CACNA1D, CACNA1H, CLCN2 3

Step 5: For confirmed familial cases:

• Cascade screening of all first-degree relatives is mandatory 1, 2
• Aldosterone suppression testing becomes unnecessary in mutation-positive family members 1

Critical Management Implications

Patients with confirmed familial hyperaldosteronism do not require aldosterone suppression testing before treatment 1. This avoids the burdensome diagnostic workup and allows immediate initiation of targeted therapy, which is particularly important given that these patients often present young with severe disease requiring aggressive management.

The distinction between germline (familial) and somatic (sporadic adenoma) mutations is clinically crucial: germline mutations necessitate family screening and may require different surgical approaches (bilateral adrenalectomy for severe FH-III mutations), while somatic mutations are confined to the adenoma and don't affect family members 2, 3.