Endocrinology

Understanding Familial Hyperaldosteronism Type II and Red Flags

At a Glance

Familial hyperaldosteronism type II is an inherited cause of excess aldosterone, often linked to CLCN2 variants. It can look like ordinary primary aldosteronism, so early-onset high blood pressure, family history, genetic testing, and clear emergency warning signs are important.

Finding out you have Primary Aldosteronism (PA) — a condition where your adrenal glands produce too much of the hormone aldosterone — often leads to a search for why it happened ^[1]. While most cases are “sporadic” (occurring by chance), some are inherited. Familial Hyperaldosteronism Type II (FH-II) is a genetic form of PA that looks biochemically identical to the more common version in routine blood tests, which often leads to a long “diagnostic odyssey” before the correct cause is identified ^[2]^[3].

What is Familial Hyperaldosteronism Type II?

FH-II is an inherited condition that is most commonly linked to a pathogenic variant (a mutation) in the CLCN2 gene ^[4]. This gene provides instructions for making a chloride channel in your adrenal glands. When this channel doesn’t work correctly, it causes the adrenal cells to become overactive, which triggers the overproduction of aldosterone ^[5]^[6].

Because the laboratory markers for FH-II (high aldosterone, low renin, and sometimes low potassium) are the same as in sporadic PA, FH-II is frequently missed ^[2]. Doctors may only suspect it if you are diagnosed at a young age or if several members of your family also have PA or early-onset high blood pressure ^[4]^[7]. A genetic test looking for pathogenic variants can confirm the diagnosis, though a negative result does not completely rule out familial PA.

Recognizing Urgent Situations and Emergencies

Most people living with PA or FH-II deal with “routine” symptoms like baseline high blood pressure or mild fatigue ^[8]. However, because PA causes the body to lose potassium and hold onto salt, it can occasionally trigger life-threatening crises.

Use the table below to distinguish between symptoms that require routine care, urgent same-day advice, and immediate emergency care (911 or the nearest ER).

Category	Routine (Discuss at Next Visit)	Urgent (Call Clinician Today)	Emergency (Go to ER / Call 911)
Potassium (Hypokalemia)	Mild muscle cramps or feeling tired ^[8].	New palpitations, fainting, or rapidly falling potassium on a lab test ^[8].	Severe Weakness/Paralysis: Inability to lift your arms/legs or walk; a “heavy” feeling ^[9]^[10]. Respiratory Distress: Difficulty breathing ^[11]^[12].
Blood Pressure	Blood pressure that is higher than your goal (e.g., 150/95) but you feel normal ^[13].	Repeated readings around 180/120 or higher, even if you have no other symptoms ^[13].	Neurological Changes: Sudden confusion, trouble speaking, vision loss, or weakness on one side of the body (signs of a stroke) ^[14]. Chest/Back Pain: Severe chest tightness, shortness of breath, or “tearing” pain in the back ^[15]^[16].
Muscles & Kidneys	General aches or mild “heavy” legs after exercise.	Swelling in the legs, or significantly reduced urine output.	Rhabdomyolysis: Severe muscle pain combined with very dark or “tea-colored” urine ^[10]^[17].

What is NOT an Emergency?

It is important to remember that having a moderately high blood pressure reading (such as 150/95) is common in PA and is generally not an emergency if you feel normal ^[13]. Wait a few minutes, rest, and re-check it.

Similarly, a slightly low potassium level (between 3.0 and 3.5 mEq/L) is concerning, but it is not automatically an ER problem. However, it cannot reliably be managed by diet alone; it requires a clinician-directed plan for supplements or medication changes based on your symptoms and kidney function ^[18]^[17].

Emergency care is reserved for acute target-organ damage—when the high pressure or severely low potassium begins to physically stop your heart, lungs, brain, or muscles from working correctly ^[12]^[14].

Why FH-II is Often Overlooked

You may have spent years being told you simply have “essential hypertension”. FH-II is often only discovered when:

Age of Onset: A patient is diagnosed with high blood pressure in their teens, 20s, or 30s ^[2].
Family History: Multiple relatives are found to have early-onset high blood pressure ^[1].
Genetic Testing: A doctor specifically orders a genetic panel testing for CLCN2 and other genes after primary aldosteronism is diagnosed ^[7].

If you have a confirmed CLCN2 pathogenic variant, the condition typically affects both adrenal glands (bilateral), meaning it is usually managed with medication rather than surgery ^[1]^[19]. Understanding your genetic status can help direct your care and allow your relatives to pursue cascade testing ^[4]^[14].

Common questions in this guide

What is familial hyperaldosteronism type II?

Familial hyperaldosteronism type II is an inherited form of primary aldosteronism, a condition in which the adrenal glands make too much aldosterone. It is often associated with a pathogenic change in the CLCN2 gene and can lead to high blood pressure and sometimes low potassium.

How is FH-II diagnosed if it looks like ordinary primary aldosteronism?

Routine blood tests can show high aldosterone, low renin, and sometimes low potassium in both FH-II and noninherited primary aldosteronism. A genetic test that looks for a pathogenic CLCN2 variant can support or confirm FH-II, but a negative result does not completely exclude a familial form.

Who should ask about genetic testing for FH-II?

Genetic testing is worth discussing when high blood pressure or primary aldosteronism begins unusually early, especially in the teens, 20s, or 30s, or when several relatives have early-onset high blood pressure or primary aldosteronism. A clinician can decide which genes to test and explain what the results mean.

When does high blood pressure with FH-II need urgent or emergency care?

A blood pressure reading around 180/120 or higher that repeats should prompt same-day contact with a clinician, even if you feel well. Go to the emergency department or call 911 for sudden confusion, trouble speaking, vision loss, one-sided weakness, severe chest or back pain, or breathing difficulty.

What low-potassium symptoms are warning signs?

Mild cramps or tiredness can be discussed at a routine visit, while new palpitations, fainting, or a rapidly falling potassium result need same-day advice. Severe weakness, paralysis, inability to walk, or trouble breathing is an emergency.

Does a CLCN2 variant change treatment or affect relatives?

A confirmed CLCN2 variant usually means both adrenal glands are involved, so treatment is generally medication rather than surgery. Because the variant can run in families, relatives may discuss cascade genetic testing with a clinician or genetics professional.

Answer a question to get research tailored to you. Your answers are private.

Get notified when new evidence is published on Familial hyperaldosteronism type II.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.

Curated prompts to bring to your next appointment.

1.Is my age of onset or family history of high blood pressure suspicious for a genetic form like FH-II?
2.Should I be tested for the CLCN2 gene mutation to determine if my condition is inherited?
3.If I have a confirmed pathogenic variant for FH-II, when should my relatives undergo cascade genetic testing?
4.At what blood pressure reading should I call your office for same-day advice, and at what reading should I go to the Emergency Room?
5.Given my specific potassium levels, what are the early signs of a rapid drop that I should watch for?

Key takeaways

FH-II is an inherited form of primary aldosteronism, often linked to a pathogenic CLCN2 variant, that causes excess aldosterone and may lead to high blood pressure and low potassium.
FH-II can be missed because its routine blood-test pattern resembles sporadic primary aldosteronism; young-onset hypertension or a family history should prompt discussion of genetic testing.
Repeated blood pressure readings around 180/120 or higher warrant same-day clinician advice, while stroke-like symptoms, severe chest or back pain, or breathing difficulty require emergency care.
Palpitations, fainting, and rapidly falling potassium need prompt clinical advice, while severe weakness, paralysis, or difficulty breathing are emergencies.
When a CLCN2 variant is confirmed, both adrenal glands are usually involved, so medication is generally used and relatives may consider cascade testing.

References (19)

1
Pathogenesis of Familial Hyperaldosteronism Type II: New Concepts Involving Anion Channels.
Stowasser M, Wolley M, Wu A, et al.
Current hypertension reports 2019; (21(4)):31 doi:10.1007/s11906-019-0934-y.
PMID: 30949771
2
Differences in the clinical and hormonal presentation of patients with familial and sporadic primary aldosteronism.
Araujo-Castro M, Parra P, Martín Rojas-Marcos P, et al.
Frontiers in endocrinology 2024; (15()):1336306 doi:10.3389/fendo.2024.1336306.
PMID: 38495792
3
What We Know about and What Is New in Primary Aldosteronism.
Ekman N, Grossman AB, Dworakowska D
International journal of molecular sciences 2024; (25(2)) doi:10.3390/ijms25020900.
PMID: 38255973
4
CLCN2 chloride channel mutations in familial hyperaldosteronism type II.
Scholl UI, Stölting G, Schewe J, et al.
Nature genetics 2018; (50(3)):349-354 doi:10.1038/s41588-018-0048-5.
PMID: 29403011
5
A gain-of-function mutation in the CLCN2 chloride channel gene causes primary aldosteronism.
Fernandes-Rosa FL, Daniil G, Orozco IJ, et al.
Nature genetics 2018; (50(3)):355-361 doi:10.1038/s41588-018-0053-8.
PMID: 29403012
6
Elevated aldosterone and blood pressure in a mouse model of familial hyperaldosteronism with ClC-2 mutation.
Schewe J, Seidel E, Forslund S, et al.
Nature communications 2019; (10(1)):5155 doi:10.1038/s41467-019-13033-4.
PMID: 31727896
7
Diagnosis and treatment of primary aldosteronism.
Reincke M, Bancos I, Mulatero P, et al.
The lancet. Diabetes & endocrinology 2021; (9(12)):876-892 doi:10.1016/S2213-8587(21)00210-2.
PMID: 34798068
8
Normotensive hypokalemic primary hyperaldosteronism mimicking clinical features of anorexia nervosa in a young patient: A case report.
Huang YC, Tsai MH, Fang YW, Tu ML
Medicine 2020; (99(29)):e20826 doi:10.1097/MD.0000000000020826.
PMID: 32702825
9
Should we suspect primary aldosteronism in patients with hypokalaemic rhabdomyolysis? A systematic review.
Díaz-López EJ, Villar-Taibo R, Rodriguez-Carnero G, et al.
Frontiers in endocrinology 2023; (14()):1257078 doi:10.3389/fendo.2023.1257078.
PMID: 37810894
10
Primary aldosteronism with hypokalemic rhabdomyolysis: a case report and review of the literature.
Shi P, Wang C, Lyu Y
Journal of medical case reports 2024; (18(1)):362 doi:10.1186/s13256-024-04708-8.
PMID: 39118166
11
Respiratory failure and rhabdomyolysis caused by severe hypokalemia in a young female with hypertension: a rare critical condition in primary aldosteronism.
Bazroodi H, Kamran H, Haghpanah A, et al.
BMC urology 2024; (24(1)):225 doi:10.1186/s12894-024-01619-0.
PMID: 39407241
12
Lethal Arrhythmia Induced by Severe Hypokalemia with Primary Aldosteronism: A Case Report and Literature Review.
Hirose R, Tsurutani Y, Nakatsue T, et al.
Internal medicine (Tokyo, Japan) 2024; (63(10)):1405-1413 doi:10.2169/internalmedicine.1931-23.
PMID: 37813618
13
Prevalence of Primary Aldosteronism in Newly Diagnosed Hypertensive Patients in Primary Care.
Asbach E, Kellnar A, Bekeran M, et al.
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association 2022; (130(12)):801-805 doi:10.1055/a-1938-4242.
PMID: 36070803
14
Cardiovascular events and target organ damage in primary aldosteronism compared with essential hypertension: a systematic review and meta-analysis.
Monticone S, D'Ascenzo F, Moretti C, et al.
The lancet. Diabetes & endocrinology 2018; (6(1)):41-50 doi:10.1016/S2213-8587(17)30319-4.
PMID: 29129575
15
Primary aldosteronism complicated by early-onset heart failure in a young male with a coexisting DMD variant: A case report and literature review.
Song X, Qian S, Jia M, et al.
Medicine 2025; (104(45)):e45443 doi:10.1097/MD.0000000000045443.
PMID: 41204571
16
Malignant Hypertension and Torsades De Pointes as Initial Presentations of Primary Aldosteronism.
Li Y
JACC. Case reports 2026; (31(11)):106868 doi:10.1016/j.jaccas.2026.106868.
PMID: 41661122
17
Hypertensive Crisis with Neurological Impairment Mimicking a Guillain-Barrè Syndrome: Searching for a Link.
Mazza A, Lucchetta M, Torin G, et al.
High blood pressure & cardiovascular prevention : the official journal of the Italian Society of Hypertension 2018; (25(4)):421-424 doi:10.1007/s40292-018-0283-y.
PMID: 30298226
18
Concurrent Adrenal Adenoma, Unilateral Adrenal Hyperplasia, and Bilateral Renal Artery Stenosis in a 61-Year-Old Man.
Mrabet S, Jaziri A, Zellama D, et al.
American journal of men's health 2024; (18(6)):15579883241309769 doi:10.1177/15579883241309769.
PMID: 39718165
19
Timeline of Advances in Genetics of Primary Aldosteronism.
Meyer LS, Reincke M, Williams TA
Experientia supplementum (2012) 2019; (111()):213-243 doi:10.1007/978-3-030-25905-1_11.
PMID: 31588534

This page is for informational purposes only and does not constitute medical advice about familial hyperaldosteronism type II. Your clinician should interpret your blood pressure, potassium results, and genetic testing; seek emergency care for severe symptoms.

Guide Contents