Familial Hyperaldosteronism Type Research Articles

Primary aldosteronism and cardiovascular risk. Review

Primary aldosteronism (PA), a significant and curable cause of secondary hypertension, occurs in 5—10% of hypertensive patients, with prevalence dependent on the severity of hypertension. The main etiologies of PA include bilateral idiopathic hypertrophy (BIH) and aldosterone‑producing adenoma (APA), while less common causes include unilateral hyperplasia, familial hyperaldosteronism (FH) types I—IV, aldosterone‑producing carcinoma, and ectopic aldosterone synthesis. This condition, characterized by excessive secretion of aldosterone, leads to increased reabsorption of sodium and water along with potassium loss, culminating in the distinct clinical signs of elevated aldosterone, suppressed renin, and hypertension. It should be noted that hypokalemia is present in only 28% of patients with PA and is not the main indicator. The association of PA with an increased risk profile for cardiovascular disease, regardless of blood pressure level, is notable. Patients with PA show an increased rate of cardiovascular events compared to patients with essential hypertension, adjusted for age, sex, and blood pressure level. Despite its prevalence, PA often remains undiagnosed, highlighting the need for enhanced screening protocols. The diagnostic process for PA involves a three‑pronged assessment: the aldosterone/renin ratio (ARR) as the initial screening tool, followed by confirmatory and subtype tests. A positive ARR requires confirmatory testing to rule out false positives. Examination to detect PA should be carried out in patients with arterial hypertension: moderate (> 160—179/100—109 mm Hg) or severe (> 180/110 mm Hg); resistant to treatment; with idiopathic or diuretic‑induced hypokalemia; with an accidentally diagnosed tumor of the adrenal glands; if first‑generation relatives are diagnosed with PA, or family history indicates early onset of arterial hypertension, or cerebrovascular disorders at a young age (< 40 years); with accompanying obstructive sleep apnea.

Differences in the clinical and hormonal presentation of patients with familial and sporadic primary aldosteronism.

To compare the clinical and hormonal characteristics of patients with familial hyperaldosteronism (FH) and sporadic primary aldosteronism (PA). A systematic review of the literature was performed for the identification of FH patients. The SPAIN-ALDO registry cohort of patients with no suspicion of FH was chosen as the comparator group (sporadic group). A total of 360 FH (246 FH type I, 73 type II, 29 type III, and 12 type IV) cases and 830 sporadic PA patients were included. Patients with FH-I were younger than sporadic cases, and women were more commonly affected (P = 0.003). In addition, the plasma aldosterone concentration (PAC) was lower, plasma renin activity (PRA) higher, and hypokalemia (P < 0.001) less frequent than in sporadic cases. Except for a younger age (P < 0.001) and higher diastolic blood pressure (P = 0.006), the clinical and hormonal profiles of FH-II and sporadic cases were similar. FH-III had a distinct phenotype, with higher PAC and higher frequency of hypokalemia (P < 0.001), and presented 45 years before sporadic cases. Nevertheless, the clinical and hormonal phenotypes of FH-IV and sporadic cases were similar, with the former being younger and having lower serum potassium levels. In addition to being younger and having a family history of PA, FH-I and III share other typical characteristics. In this regard, FH-I is characterized by a low prevalence of hypokalemia and FH-III by a severe aldosterone excess causing hypokalemia in more than 85% of patients. The clinical and hormonal phenotype of type II and IV is similar to the sporadic cases.

What We Know about and What Is New in Primary Aldosteronism.

Primary aldosteronism (PA), a significant and curable cause of secondary hypertension, is seen in 5-10% of hypertensive patients, with its prevalence contingent upon the severity of the hypertension. The principal aetiologies of PA include bilateral idiopathic hypertrophy (BIH) and aldosterone-producing adenomas (APAs), while the less frequent causes include unilateral hyperplasia, familial hyperaldosteronism (FH) types I-IV, aldosterone-producing carcinoma, and ectopic aldosterone synthesis. This condition, characterised by excessive aldosterone secretion, leads to augmented sodium and water reabsorption alongside potassium loss, culminating in distinct clinical hallmarks: elevated aldosterone levels, suppressed renin levels, and hypertension. Notably, hypokalaemia is present in only 28% of patients with PA and is not a primary indicator. The association of PA with an escalated cardiovascular risk profile, independent of blood pressure levels, is notable. Patients with PA exhibit a heightened incidence of cardiovascular events compared to counterparts with essential hypertension, matched for age, sex, and blood pressure levels. Despite its prevalence, PA remains frequently undiagnosed, underscoring the imperative for enhanced screening protocols. The diagnostic process for PA entails a tripartite assessment: the aldosterone/renin ratio (ARR) as the initial screening tool, followed by confirmatory and subtyping tests. A positive ARR necessitates confirmatory testing to rule out false positives. Subtyping, achieved through computed tomography and adrenal vein sampling, aims to distinguish between unilateral and bilateral PA forms, guiding targeted therapeutic strategies. New radionuclide imaging may facilitate and accelerate such subtyping and localisation. For unilateral adrenal adenoma or hyperplasia, surgical intervention is optimal, whereas bilateral idiopathic hyperplasia warrants treatment with mineralocorticoid antagonists (MRAs). This review amalgamates established and emerging insights into the management of primary aldosteronism.

FRI190 Catching A Chimera: A Case Of Suspected Glucocorticoid Remediable Aldosteronism

Abstract Disclosure: A. Khan: None. B. Ramchandani: None. H.B. Aftab: None. Introduction: Familial hyperaldosteronism type 1 (FH-I), also known as glucocorticoid remediable aldosteronism (GRA) is responsible for 1% of cases of primary aldosteronism (PA). It is caused by a chimeric fusion of the CYP11B2 and CYP11B1 genes resulting in ACTH-sensitive aldosterone production. We describe a case of suspected GRA and outline the diagnosis of this rare condition. Case. A 52-year-old female with history of type 2 diabetes mellitus, obesity, sleep apnea, SVT with ablation presented with long-standing history of resistant hypertension (HTN). HTN was diagnosed in her late twenties. She was previously trialed on eight different classes of antihypertensive medications excluding mineralocorticoid antagonists or potassium-sparing diuretics but HTN remained uncontrolled. Current regimen included hydralazine, nebivolol, and furosemide. Her sister had HTN diagnosed in her forties, a nephew with HTN diagnosed in his early twenties and mother with HTN with unclear age of diagnosis. Her systolic and diastolic BP averaged 150 mmHg and 90 mmHg, respectively, on both home and clinic monitoring. Physical examination was significant for mild cushingoid appearance. Screening tests for pheochromocytoma and hypercortisolism were normal. Plasma aldosterone concentration (PAC) was noted to be at 14.4 ng/dl (&amp;lt;39.2) with a plasma renin activity (PRA) of &amp;lt;0.6 ng/mL/h (2.9 - 10.8), with aldosterone to renin ratio (ARR) of 24. Repeat testing showed PAC of 15.1 ng/dl, PRA&amp;lt;0.6 ng/ml/hr (ARR: 25.1) with potassium of 3.3 mmol/L (3.5 -5.1). PAC levels remained unsuppressed above 10 ng/dL following four-hour, seated, 2 L IV saline suppression test with serum potassium of 3.5 mmol/L. CT abdomen showed normal appearance of the adrenal glands. Given early age of onset of HTN and strong family history, 3-day dexamethasone test was performed using 1 mg oral dexamethasone every 12 hours following which PAC suppressed to &amp;lt;1 ng/dl. Patient was started on spironolactone 25 mg twice daily and at the time of writing is awaiting genetic testing to confirm the diagnosis of GRA. Discussion: GRA is a rare subtype of PA which has an increased risk of cardiovascular and cerebrovascular complications. Our case highlights the importance of screening for GRA in patients who have a personal and/or family history of early onset HTN who have screened positive for PA. Genetic testing for chimeric CYP11B1/B2 gene is the confirmatory step of diagnosis, however, a 3-day dexamethasone suppression test can be used to screen for GRA with a high sensitivity. Elevated levels of urine 18-hydroxycortisol and 18-oxocortisol are also noted but these are not widely available tests. Treatment of GRA is with medical management only; since surgical intervention is not required; proper diagnosis can also save the patient from unnecessary and invasive tests such as adrenal vein sampling. Presentation: Friday, June 16, 2023

Relevance of KCNJ5 in Pathologies of Heart Disease.

Abnormalities in G-protein-gated inwardly rectifying potassium (GIRK) channels have been implicated in diseased states of the cardiovascular system; however, the role of GIRK4 (Kir3.4) in cardiac physiology and pathophysiology has yet to be completely understood. Within the heart, the KACh channel, consisting of two GIRK1 and two GIRK4 subunits, plays a major role in modulating the parasympathetic nervous system's influence on cardiac physiology. Being that GIRK4 is necessary for the functional KACh channel, KCNJ5, which encodes GIRK4, it presents as a therapeutic target for cardiovascular pathology. Human variants in KCNJ5 have been identified in familial hyperaldosteronism type III, long QT syndrome, atrial fibrillation, and sinus node dysfunction. Here, we explore the relevance of KCNJ5 in each of these diseases. Further, we address the limitations and complexities of discerning the role of KCNJ5 in cardiovascular pathophysiology, as identical human variants of KCNJ5 have been identified in several diseases with overlapping pathophysiology.

S-13-5: UPDATES ON FAMILIAL HYPERALDSOTERONISM

The first reported (Sutherland et al. 1966) form of familial primary aldosteronism (PA) involved a father and son and was glucocorticoid-remediable (familial hyperaldosteronism type I, FH-I). In 1992, Lifton and colleagues elucidated its causation, a hybrid gene mutation composed of CYP11B1 (encoding 11beta-hydroxylase) regulatory sequences and CYP11B2 (aldosterone synthase) coding sequences causing ACTH-regulated aldosterone overproduction and hypertension, both readily controlled by low-dose glucocorticoid administration. Expression of aldosterone synthase activity within zona fasciculata (ZF) explained overproduction of hybrid steroids, 18-hydroxy- and 18-oxocortisol. Since 2011, PA-causing germline mutations in another four genes (three associated with FH) have been reported. While three encode cation channels (KCNJ5, CACNA1H and CACNA1D), one encodes an anion channel (CLCN2). FH-III is caused by inheritance of gain-of-function mutations in KCNJ5, encoding an inwardly rectifying potassium channel (GIRK-4). Depending on the exact mutation involved, phenotype varies from very severe (profound PA, hybrid steroid elevation and ZF hyperplasia and requiring bilateral adrenalectomy to control hypertension) to mild (absence of above with PA controllable with spironolactone). Most pedigrees demonstrate early-onset hypertension. Mutations reduce selectivity of GIRK-4 to potassium, permitting entry of sodium into the adrenal cortical cell, which results in cell depolarization and calcium influx, leading to increased expression of CYP11B2 and aldosterone synthesis. A gain-of-function mutation in CACNA1H, encoding a T-type voltage-gated calcium channel, was found in five of 40 subjects with early-onset PA and three relatives with early-onset hypertension (FH-IV). Adrenals appeared normal on imaging. The mutation shifts activation of zona glomerulosa (ZG) cells to a more hyperpolarized potential and slows inactivation, putatively resulting in increased calcium influx and aldosterone production. Germline mutations in CACNA1D, encoding an L-type voltage-gated calcium channel highly expressed in ZG, were identified in two of 100 individuals with early-onset PA. Both occurred de novo, and were associated with seizures and a variety of neurological abnormalities (PASNA). Both mutations cause channel activation at less depolarized membrane potentials, and one nearly abolished channel inactivation. In a large Australian family with FH-II, a mutation was found in CLCN2 encoding a chloride channel, ClC-2. CLCN2 mutations were found in another seven of 80 individuals with early-onset PA. A concurrent report found a CLCN2 mutation in one of 12 subjects with early-onset PA. PA due to CLCN2 mutations responds well to medical treatment. In the adrenal, ClC-2 localizes predominantly to ZG and mutations predispose cell depolarization, leading to calcium influx via activation of voltage-gated calcium channels and increased aldosterone production.

Management and Outcomes of Primary Aldosteronism in Pregnancy: A Systematic Review.

Primary aldosteronism (PA) in pregnancy (PAP) can be a serious condition and is challenging to diagnose. This study was conceived to help in the diagnosis of PAP and provide suggestions on management of PAP based on evidence retrieved using a Population, Intervention, Comparison, and Outcome search strategy. Based on the changes of aldosterone and renin occurring in normal pregnancies, we developed a nomogram that will allow to identify PAP cases. Moreover, we found that published PAP cases fell into 4 main groups differing for management and outcomes: (1) unilateral medically treated, (2) unilateral surgically treated, (3) bilateral medically treated and (4) familial forms. Results showed that complications involved 62.2% of pregnant women with nonfamilial PA and 18.5% of those with familial hyperaldosteronism type I. Adrenalectomy during pregnancy in women with PAP did not improve maternal and fetal outcomes, over medical treatment alone. Moreover, cure of maternal hypertension and mother and baby outcome were better when unilateral PA was discovered and surgically treated before or after pregnancy. Therefore, fertile women with arterial hypertension should be screened for PA before pregnancy and, if necessary, subtyped to identify unilateral forms of PA. This will allow to furnish adequate counseling, a chance for surgical cure and, therefore, for a pregnancy not complicated by aldosterone excess.

HIPERTENSI SEKUNDER: GEN-GEN YANG MERANGSANG PEREMBESAN ALDOSTERON YANG BERLEBIHAN

Hypertension is highly prevalent in Malaysia and even the rest of the world. Primary aldosteronism (PA) is one of the most common treatable cause of secondary hypertension. PA occurs due to excessive secretion of aldosterone in the adrenal glands. Up to one in five resistant hypertension cases are due to PA. Therefore, there are a high number of individuals who have the potential to be cured of their hypertension. However, this is difficult to achieve due to limitations in the procedure of diagnosing the PA disease. The challenge now is to know the best usage of available diagnostic methods to detect those who would most likely be cured of hypertension which may be associated with the genotype of the disease. In the past decade, five genes have been found to cause excess aldosterone production in aldosteroneproducing adenomas (APAs), namely KCNJ5, ATP1A1, ATP2B3, CACNA1D and CTNNB1. These somatic mutations have been found to activate the intracellular signaling pathway that regulates aldosterone production. Studies on bilateral adrenal hyperplasia (BAH) samples also have identified the genetic causes for the many hereditary hyperaldosteronism, namely familial hyperaldosteronism types I, II, III, and IV/V. Herein we review the genetic factors of PA as a result of either aldosterone-stimulating somatic mutations or germline variants, and the associated clinical phenotype. Keywords: Primary aldosteronism; hypertension; hyperaldosteronism; mutation

Characteristics and Outcomes in Primary Aldosteronism Patients Harboring Glucocorticoid-Remediable Aldosteronism.

The clinical characteristics and surgical prognosis of glucocorticoid-remediable aldosteronism (GRA, also known as familial hyperaldosteronism type 1, FH-I) have not been widely studied. Using data from the Taiwan Primary Aldosteronism Investigation (TAIPAI) registry retrospectively, we describe the associated clinical factors for GRA and clinical predictors of surgical outcomes among identified GRA patients. We found 79 GRA-positive (51.2 ± 13.8 years; women 39 (49.4%)) and 114 GRA-negative primary aldosteronism (PA) patients matched with age, gender, and body mass index. Lower plasma aldosterone concentrations (PACs) and aldosterone-renin ratios were found among GRA-positive individuals. Multivariable logistic regression demonstrated that a PAC ≤ 40 ng/dL could predict concealed GRA individuals (OR 0.523, p = 0.037). Low serum potassium (OR 0.285, p = 0.008), but not the presence of GRA, was associated with hypertension-remission. Of note, PRA (OR 11.645, p = 0.045) and hypokalemia (OR 0.133, p = 0.048) were associated with hypertension-remission in GRA patients. Unilateral primary aldosteronism patients harboring concomitant GRA were not associated with inferior hypertension-remission after an adrenalectomy. Low serum potassium and high PRA were positively associated with hypertension-remission in GRA patients.

Progress on Genetic Basis of Primary Aldosteronism.

Primary aldosteronism (PA) is a heterogeneous group of disorders caused by the autonomous overproduction of aldosterone with simultaneous suppression of plasma renin activity (PRA). It is considered to be the most common endocrine cause of secondary arterial hypertension (HT) and is associated with a high rate of cardiovascular complications. PA is most often caused by a bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenoma (APA); rarer causes of PA include genetic disorders of steroidogenesis (familial hyperaldosteronism (FA) type I, II, III and IV), aldosterone-producing adrenocortical carcinoma, and ectopic aldosterone-producing tumors. Over the last few years, significant progress has been made towards understanding the genetic basis of PA, classifying it as a channelopathy. Recently, a growing body of clinical evidence suggests that mutations in ion channels appear to be the major cause of aldosterone-producing adenomas, and several mutations within the ion channel encoding genes have been identified. Somatic mutations in four genes (KCNJ5, ATP1A1, ATP2B3 and CACNA1D) have been identified in nearly 60% of the sporadic APAs, while germline mutations in KCNJ5 and CACNA1H have been reported in different subtypes of familial hyperaldosteronism. These new insights into the molecular mechanisms underlying PA may be associated with potential implications for diagnosis and therapy.

Testosterone inhibits human wild-type and chimeric aldosterone synthase activity in vitro

Familial hyperaldosteronism type I is caused by the generation of a chimeric aldosterone synthase enzyme (ASCE) which is regulated by ACTH instead of angiotensin II. We have reported that in vitro, the wild-type (ASWT) and chimeric aldosterone synthase (ASCE) enzymes are inhibited by progesterone and estradiol does not affect their activity. To explore the direct action of testosterone on ASWT and ASCE enzymes. HEK-293 cells were transiently transfected with vectors containing the full ASWT or ASCE cDNAs. The effect of testosterone on AS enzyme activities was evaluated incubating HEK-cells transfected with enzyme vectors and adding deoxycorticosterone (DOC) alone or DOC plus increasing doses of testosterone. Aldosterone production was measured by HPLC-MS/MS. Docking of testosterone within the active sites of both enzymes was performed by modelling in silico. In this system, testosterone inhibited ASWT (90% inhibition at five pM, 50% inhibitory concentration (IC50) =1.690 pM) with higher efficacy andpotency than ASCE (80% inhibition at five pM, IC50=3.176 pM). Molecular modelling studies showed different orientation of testosterone in ASWT and ASCE crystal structures. The inhibitory effect of testosterone on ASWT or ASCE enzymes is a novel non-genomic testosterone action, suggesting that further clinical studies are needed to assess the role of testosterone in the screening and diagnosis of primary aldosteronism.

Resistant Hypertension Due to Familial Hyperaldosteronism Type III: First Report From Indian Sub-Continent

Background: Familial hyperaldosteronism type III (FH-III) is caused by germline mutations in KCNJ5 gene. FH-III presents with phenotypic variability from spironolactone-responsive hypertension to massive adrenal hyperplasia requiring bilateral adrenalectomy. Till date, seven different pathogenic mutations in KCNJ5 gene have been identified. Here we describe a sporadic FH-III case, due to a Gly151Arg mutation, first from Indian subcontinent, presenting with extremely high plasma aldosterone concentration (PAC) values, further expanding our knowledge of this rare condition. Clinical Case: A 24-year-old female, symptomatic since age of 5 years with periodic limb weakness and gradual increase in frequency of episodes over the years. Her blood pressure (BP) was recorded for first time at 9 years of age, and it was 170/110 mm Hg. On evaluation at this time, PAC was highly elevated at 1007 ng/dL and plasma renin activity (PRA) was suppressed at 0.04 ng/ml/h with aldosterone renin ratio (ARR) of 25,175 ng/dL per ng/mL/h (>20 suggestive of primary aldosteronism). CT scan demonstrated mild enlargement of bilateral adrenal glands. A presumptive diagnosis of Glucocorticoid-remediable aldosteronism was made. She was started on dexamethasone, spironolactone and nifedipine but was not improved. Dexamethasone was stopped after 1 year of initiation. Before presenting to our referral center in 2018, she was having uncontrolled hypertension with recurrent episodes of hypokalemic paralysis. She was on maximal doses on four antihypertensive agents, further increased to six agents (including spironolactone 100 mg BD), and potassium chloride supplementation (120 mEq/day). Despite this, she had a serum potassium of 2.6 mEq/L. Her biochemical investigations demonstrated that PAC was 2070 ng/dL, direct renin concentration (DRC) was 2.35 µIU/mL (PRA 0.2 ng/ml/h) and ARR was 880.9 ng/dL per µIU/mL. CT scan revealed massive bilateral adrenal hyperplasia. Genetic analysis by whole exome sequencing detected KCNJ5 (p.Gly151Arg) mutation, confirming the diagnosis of FH-III. She was subjected to bilateral adrenalectomy and she became normokalemic. Dramatic reduction in antihypertensives with BP control achieved only on amlodipine post-operatively. Genetic testing of family members was not done but they were normotensive and normokalemic. Histopathological examination revealed bilateral adrenal hyperplasia. PAC levels up to 297 ng/dL have been described previously in FH-III but our patient had exceedingly high-level of 2070 ng/dL. Conclusion: This case demonstrates florid clinical and biochemical manifestations of FH-III and gradual worsening of symptoms, consistent with progression of disease with age. It illustrates that proper investigations and treatment can lead to remission of symptoms. Further studies are warranted to elucidate the full clinical and biochemical spectrum of FH-III.

Enhanced Ca2+ signaling, mild primary aldosteronism, and hypertension in a familial hyperaldosteronism mouse model (Cacna1hM1560V/+)

Gain-of-function mutations in the CACNA1H gene (encoding the T-type calcium channel CaV3.2) cause autosomal-dominant familial hyperaldosteronism type IV (FH-IV) and early-onset hypertension in humans. We used CRISPR/Cas9 to generate Cacna1hM1560V/+ knockin mice as a model of the most common FH-IV mutation, along with corresponding knockout mice (Cacna1h-/- ). Adrenal morphology of both Cacna1hM1560V/+ and Cacna1h-/- mice was normal. Cacna1hM1560V/+ mice had elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism). Their adrenal Cyp11b2 (aldosterone synthase) expression was increased and remained elevated on a high-salt diet (relative autonomy, characteristic of primary aldosteronism), but plasma aldosterone was only elevated in male animals. The systolic blood pressure of Cacna1hM1560V/+ mice was 8 mmHg higher than in wild-type littermates and remained elevated on a high-salt diet. Cacna1h-/- mice had elevated renal Ren1 (renin-1) expression but normal adrenal Cyp11b2 levels, suggesting that in the absence of CaV3.2, stimulation of the renin-angiotensin system activates alternative calcium entry pathways to maintain normal aldosterone production. On a cellular level, Cacna1hM1560V/+ adrenal slices showed increased baseline and peak intracellular calcium concentrations in the zona glomerulosa compared to controls, but the frequency of calcium spikes did not rise. We conclude that FH-IV, on a molecular level, is caused by elevated intracellular Ca2+ concentrations as a signal for aldosterone production in adrenal glomerulosa cells. We demonstrate that a germline Cacna1h gain-of-function mutation is sufficient to cause mild primary aldosteronism, whereas loss of CaV3.2 channel function can be compensated for in a chronic setting.

Identification of Somatic Mutations in CLCN2 in Aldosterone-Producing Adenomas.

Somatic mutations driving aldosterone production have been identified in approximately 90% of aldosterone-producing adenomas (APAs) using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided DNA sequencing approach. In the present study, using CYP11B2-guided whole-exome sequencing (WES) and targeted amplicon sequencing, we detected 2 somatic variants in CLCN2 in 2 APAs that were negative for currently known aldosterone-driver mutations. The CLCN2 gene encodes the voltage-gated chloride channel ClC-2. CLCN2 germline variants have previously been shown to cause familial hyperaldosteronism type II. Somatic mutations in CLCN2 were identified in 2 of 115 APAs, resulting in a prevalence of 1.74%. One of the CLCN2 somatic mutations (c.G71A,p.G24D) was identical to a previously described germline variant causing early-onset PA, but was present only as a somatic mutation. The second CLCN2 mutation, which affects the same region of the gene, has not been reported previously (c.64-2_74del). These findings prove that WES of CYP11B2-guided mutation-negative APAs can help determine rarer genetic causes of sporadic PA.

Molecular Basis of Primary Aldosteronism and Adrenal Cushing Syndrome.

This review reports the main molecular alterations leading to development of benign cortisol- and/or aldosterone-secreting adrenal tumors. Causes of adrenal Cushing syndrome can be divided in 2 groups: multiple bilateral tumors or adenomas secreting cortisol. Bilateral causes are mainly primary pigmented nodular adrenocortical disease, most of the time due to PRKAR1A germline-inactivating mutations, and primary bilateral macronodular adrenal hyperplasia that can be caused in some rare syndromic cases by germline-inactivating mutations of MEN1, APC, and FH and of ARMC5 in isolated forms. PRKACA somatic-activating mutations are the main alterations in unilateral cortisol-producing adenomas. In primary hyperaldosteronism (PA), familial forms were identified in 1% to 5% of cases: familial hyperaldosteronism type I (FH-I) due to a chimeric CYP11B1/CYP11B2 hybrid gene, FH-II due to CLCN-2 germline mutations, FH-III due to KCNJ5 germline mutations, FH-IV due to CACNA1H germline mutations and PA, and seizures and neurological abnormalities syndrome due to CACNA1D germline mutations. Several somatic mutations have been found in aldosterone-producing adenomas in KCNJ5, ATP1A1, ATP2B3, CACNA1D, and CTNNB1 genes.In addition to these genetic alterations, genome-wide approaches identified several new alterations in transcriptome, methylome, and miRnome studies, highlighting new pathways involved in steroid dysregulation.

SAT-549 Identification of Somatic Mutations in CLCN2 as a Cause of Aldosterone-Producing Adenomas

Background: Primary aldosteronism (PA) results from both unilateral and bilateral adrenal disease. Unilateral disease is most often caused by aldosterone-producing adenomas (APAs). We recently identified aldosterone-driver somatic mutations in approximately 90% of APAs using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided DNA sequencing approach. In the present study, we analyzed DNA from APA samples found to be mutation negative. Methods: Formalin-fixed paraffin-embedded tissue samples from PA patients who underwent adrenalectomy were studied. Genomic DNA was isolated from 118 APAs (identified by CYP11B2 IHC). Next generation sequencing (NGS) was performed to identify known aldosterone-driver mutations in KCNJ5, ATP1A1, ATP2B3, and CACNA1D. APA DNA that was mutation negative and the adjacent normal adrenal tissue DNA were subjected to Whole Exome Sequencing (WES). Results: Targeted NGS and WES detected two variants in the voltage-gated chloride channel ClC-2 (encoded by CLCN2), which were confirmed by Sanger sequencing. One of the CLCN2 mutations (p.Gly24Asp) was identical to that previously found to cause germline early-onset PA. The second CLCN2 mutation, which would affect the same region of the protein, was an unreported PA mutation (p.Met22fs). The presence of these variants in two tumors suggests that CLCN2 mutations as a cause of APAs are rare with an approximate prevalence of 1.7% (2/118 APAs). Conclusion: In this study, we identified somatic mutations in CLCN2, in two of 118 APAs. Germline variants in this gene have previously been shown to cause of familial hyperaldosteronism type II and the current findings indicate that similar mutations cause a small proportion of APAs. These findings also indicate that WES of CYP11B2-guided mutation negative APAs can help determine rarer genetic causes of sporadic PA.

Elevated aldosterone and blood pressure in a mouse model of familial hyperaldosteronism with ClC-2 mutation

Gain-of-function mutations in the chloride channel ClC-2 were recently described as a cause of familial hyperaldosteronism type II (FH-II). Here, we report the generation of a mouse model carrying a missense mutation homologous to the most common FH-II-associated CLCN2 mutation. In these Clcn2R180Q/+ mice, adrenal morphology is normal, but Cyp11b2 expression and plasma aldosterone levels are elevated. Male Clcn2R180Q/+ mice have increased aldosterone:renin ratios as well as elevated blood pressure levels. The counterpart knockout model (Clcn2−/−), in contrast, requires elevated renin levels to maintain normal aldosterone levels. Adrenal slices of Clcn2R180Q/+ mice show increased calcium oscillatory activity. Together, our work provides a knockin mouse model with a mild form of primary aldosteronism, likely due to increased chloride efflux and depolarization. We demonstrate a role of ClC-2 in normal aldosterone production beyond the observed pathophysiology.

CLCN2 clicks with aldosterone-producing adenomas, too!

Germline mutations in the chloride channel gene CLCN2 have been described as cause of familial hyperaldosteronism type II. In this issue, Dutta and colleagues in a groundbreaking study identify a somatic (tumor-specific) CLCN2 mutation in an aldosterone-producing adenoma, expanding the disease spectrum associated with CLCN2 mutations.

Timeline of Advances in Genetics of Primary Aldosteronism.

The overwhelming majority of cases of primary aldosteronism (PA) occur sporadically due to a unilateral aldosterone-producing adenoma (APA) or bilateral idiopathic adrenal hyperplasia. Familial forms of PA are rare with four subtypes defined to date (familial hyperaldosteronism types I-IV). The molecular basis of familial hyperaldosteronism type I (FH type I or glucocorticoid-remediable aldosteronism) was established in 1992; two decades later the genetic variant causing FH type III was identified and germline mutations causing FH type IV and FH type II were determined soon after. Effective diagnostic protocols and methods to detect the overactive gland in unilateral PA by adrenal venous sampling followed by laparoscopic adrenalectomy have made available APAs for scientific studies. In rapid succession, following the widespread use of next-generation sequencing, recurrent somatic driver mutations in APAs were identified in genes encoding ion channels and transporters. The development of highly specific monoclonal antibodies against key enzymes in adrenal steroidogenesis has unveiled the heterogeneous features of the diseased adrenal in PA and helped reveal the high proportion of APAs with driver mutations. We discuss what is known about the genetics of PA that has led to a clearer understanding of the disease pathophysiology.

Familial hyperaldosteronism type III a novel case and review of literature.

Less than 15% of hypertension cases in children are secondary to a primary hyperaldosteronism. This is idiopathic in 60% of the cases, secondary to a unilateral adenoma in 30% and 10% remaining by primary adrenal hyperplasia, familial hyperaldosteronism, ectopic aldosterone production or adrenocortical carcinoma.To date, four types of familial hyperaldosteronism (FH I to FH IV) have been reported. FH III is caused by germline mutations in KCNJ5, encoding the potassium channel Kir3.4. The mutations cause the channel to lose its selectivity for potassium, allowing large quantities of sodium to enter the cell. As a consequence, the membrane depolarizes, voltage-gated calcium channels open, calcium enters the cell, initiating the cascade that leads to aldosterone synthesis. Somatic mutations in KCNJ5 has also been described in aldosterone-producing adenomas. The most frequent presentation of FH III is with severe hyperaldosteronism symptoms and resistance to pharmacological therapy which leads to bilateral adrenalectomy. We will review current literature and describe a child with FH III due to a novel de novo deletion in KCNJ5 with wild phenotype as a sign of clinical variability of this disease.