Monogenic forms of low-renin hypertension: clinical and molecular insights

Genetic background of neonatal hypokalemia

Neonatal hypokalemia (defined as a serum potassium level <3.5 mEq/L) is the most common electrolyte disorder encountered in clinical practice. In addition to common secondary causes, primary genetic etiologies are also closely associated with hypokalemia. Currently, a systematic characterization of these genetic disorders is lacking, making early recognition challenging and clinical management uncertain. This review will aid clinicians by summarizing the genetic background of neonatal hypokalemia from two aspects: (1) increased excretion of K+, whereby genetic factors primarily lead to increased renal Na+ influx, decreased H+ efflux, or reduced Cl- influx, ultimately resulting in increased K+ efflux; and (2) decreased extracellular distribution of K+, whereby genetic factors result in abnormalities in transmembrane ion channels, reducing outward potassium currents or generating inward cation leak currents. We describe over ten genetic diseases associated with neonatal hypokalemia, which involve pathogenic variants in dozens of genes and affect multiple target organs, including the kidneys, intestines, and skeletal muscle. For example, in the renal tubules, pathogenic variants in the SLC12A1 gene encoding the Na+-K+-2Cl- cotransporter lead to renal K+ loss, causing Bartter syndrome type I; in intestinal epithelial cells, pathogenic variants in the SLC26A3 gene result in a defective Cl⁻-HCO₃⁻ exchanger, causing congenital chloride diarrhea; and in skeletal muscle, pathogenic variants in the CACNA1S gene impact membrane calcium ion channels resulting in hypokalemic periodic paralysis. Given the wide variety of organs and genetic alterations that can contribute to neonatal hypokalemia, we believe this review will provide valuable insights for clinical diagnosis and treatment.

Rare forms of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders due to pathogenic variants in genes encoding enzymes and cofactors involved in adrenal steroidogenesis. Although 21-hydroxylase, 11β-hydroxylase, 3β-hydroxysteroid dehydrogenase type 2, 17α-hydroxylase/17,20-lyase, P450 oxidoreductase, steroidogenic acute regulatory protein, cholesterol side-chain cleavage enzyme deficiencies are considered within the definition of CAH, the term 'CAH' is often used to refer to '21-hydroxylase deficiency (21OHD)' since 21OHD accounts for approximately 95% of CAH in most populations. The prevalence of the rare forms of CAH varies according to ethnicity and geographical location. In most cases, the biochemical fingerprint of impaired steroidogenesis points to the specific subtypes of CAH, and genetic testing is usually required to confirm the diagnosis. Despite there are significant variations in clinical characteristics and management, most data about the rare CAH forms are extrapolated from 21OHD. This review article aims to collate the currently available data about the diagnosis and the management of rare forms of CAH.

Genetics of Hypertension: From Monogenic Analysis to GETomics

Arterial hypertension is the most frequent cardiovascular risk factor all over the world, and it is one of the leading drivers of the risk of cardiovascular events and death. It is a complex trait influenced by heritable and environmental factors. To date, the World Health Organization estimates that 1.28 billion adults aged 30-79 years worldwide have arterial hypertension (defined by European guidelines as office systolic blood pressure ≥ 140 mmHg or office diastolic blood pressure ≥ 90 mmHg), and 7.1 million die from this disease. The molecular genetic basis of primary arterial hypertension is the subject of intense research and has recently yielded remarkable progress. In this review, we will discuss the genetics of arterial hypertension. Recent studies have identified over 900 independent loci associated with blood pressure regulation across the genome. Comprehending these mechanisms not only could shed light on the pathogenesis of the disease but also hold the potential for assessing the risk of developing arterial hypertension in the future. In addition, these findings may pave the way for novel drug development and personalized therapeutic strategies.

Apparent mineralocorticoid excess in Israel: a case series and literature review

BACKGROUND AND OBJECTIVE

Apparent mineralocorticoid excess (AME) syndrome is an ultra-rare autosomal-recessive tubulopathy, caused by mutations in HSD11B2, leading to excessive activation of the kidney mineralocorticoid receptor, and characterized by early-onset low-renin hypertension, hypokalemia, and risk of chronic kidney disease (CKD). To date, most reports included few patients, and none described patients from Israel. We aimed to describe AME patients from Israel and to review the relevant literature.

DESIGN

Retrospective cohort study.

METHODS

Clinical, laboratory, and molecular data from patients' records were collected.

RESULTS

Five patients presented at early childhood with normal estimated glomerular filtration rate (eGFR), while 2 patients presented during late childhood with CKD. Molecular analysis revealed 2 novel homozygous mutations in HSD11B2. All patients presented with severe hypertension and hypokalemia. While all patients developed nephrocalcinosis, only 1 showed hypercalciuria. All individuals were managed with potassium supplements, mineralocorticoid receptor antagonists, and various antihypertensive medications. One patient survived cardiac arrest secondary to severe hyperkalemia. At last follow-up, those 5 patients who presented early exhibited normal eGFR and near-normal blood pressure, but 2 have hypertension complications. The 2 patients who presented with CKD progressed to end-stage kidney disease (ESKD) necessitating dialysis and kidney transplantation.

CONCLUSIONS

In this 11-year follow-up report of 2 Israeli families with AME, patients who presented early maintained long-term normal kidney function, while those who presented late progressed to ESKD. Nevertheless, despite early diagnosis and management, AME is commonly associated with serious complications of the disease or its treatment.

Approach to Diagnosis and Management of Hypertension: A Comprehensive and Combined Pediatric and Adult Perspective

The global prevalence of primary hypertension has been increasing both in children and in the adolescent and adult populations and can be attributed to changes in lifestyle factors with an obesity epidemic, increased salt consumption, and sedentary lifestyles. Childhood blood pressure is the strongest predictor of adult hypertension. Although hypertension in adults is associated strongly with an increased risk for cardiovascular disease, chronic kidney disease, and mortality, outcomes in children are defined less clearly. In adults, major guidelines agree on a threshold of less than 120/80 mm Hg as the optimal blood pressure (BP) and recommend a target of less than 130/80 mm Hg for treatment in most cases. In children, international pediatric guidelines recommend using thresholds based on the normative distribution of BP in healthy normal-weight children. Out-of-office BP assessment is extremely useful for confirming the diagnosis of hypertension and monitoring response to treatment. Lifestyle modifications are instrumental whether coupled or not with pharmacologic management. New agents such as nonsteroidal mineralocorticoid-receptor antagonists, aminopeptidase A inhibitors, aldosterone synthase inhibitors, and dual endothelin antagonists hold significant promise for resistant hypertension. The transition from pediatric to adult care can be challenging and requires careful planning and effective coordination within a multidisciplinary team that includes patients and their families, and pediatric and adult providers.

Pathophysiologic approach in genetic hypokalemia: An update

The pathophysiology of genetic hypokalemia is close to that of non-genetic hypokalemia. New molecular pathways physiologically involved in renal and extrarenal potassium homeostasis have been highlighted. A physiological approach to diagnosis is illustrated here, with 6 cases. Mechanisms generating and sustaining of hypokalemia are discussed. After excluding acute shift of extracellular potassium to the intracellular compartment, related to hypokalemic periodic paralysis, inappropriate kaliuresis (>40mmol/24h) concomitant to hypokalemia indicates renal potassium wasting. Clinical analysis distinguishes hypertension-associated hypokalemia, due to hypermineralocorticism or related disorders. Genetic hypertensive hypokalemia is rare. It includes familial hyperaldosteronism, Liddle syndrome, apparent mineralocorticoid excess,11beta hydroxylase deficiency and Geller syndrome. In case of normo- or hypo-tensive hypokalemia, two etiologies are to be considered: chloride depletion or salt-wasting tubulopathy. Diarrhea chlorea is a rare disease responsible for intestinal chloride depletion. Due to the severity of hypokalemic metabolic alkalosis, this disease can be misdiagnosed as pseudo-Bartter syndrome. Gitelman syndrome is the most frequent cause of genetic hypokalemia. It typically associates renal sodium and potassium wasting, hypomagnesemia, conserved chloride excretion (>40mmol/24h), and low-range calcium excretion (urinary Ca/creatinine ratio<0.20mmol/mmol). Systematic analysis of hydroelectrolytic disorder and dynamic hormonal investigation optimizes indications for and orientation of genotyping of hereditary salt-losing tubulopathy.