A 3-year-old boy presented with polyuria and polydipsia for 18 months, along with growth failure. He was born prematurely, at 34 weeks of gestation, with a low birth weight. On examination, the child was severely underweight and hypertensive. Clinical history and evaluation could not identify any secondary causes of hypertension. There was no significant family history. An endocrine workup was planned, considering hypokalemia and metabolic alkalosis. This demonstrated hyporeninemic hypoaldosteronism and raised the possibility of apparent mineralocorticoid excess (AME) and Liddle syndrome. Clinical exome sequence analysis of HSD11B2 revealed a homozygous mutation in exon 5 (911A>G; p.His304Arg), which resulted in a missense mutation that confirmed the diagnosis of AME. A novel homozygous variant was found in the HSD11B2 gene in a subject with early onset hypertension associated with hypokalemic metabolic alkalosis, establishing the diagnosis of AME.

Liddle syndrome is a form of monogenic hypertension caused by mutations in the three homologous subunits of the epithelial sodium channels (ENaCs), α, β, and γ. It is characterized by early-onset refractory hypertension, hypokalemia, low renin activity, and hypoaldosteronism. In this study, we report a novel frame-shift mutation in SCNN1B responsible for Liddle syndrome in a Chinese family. DNA samples were collected from all participants. Whole-exome sequencing was performed in the proband to detect possible causative variants. Sanger sequencing was then conducted in the other family members to verify the candidate variant, and in 100 patients with hypertension and 100 normotensive controls to exclude population genetic polymorphism. We identified a novel frame-shift mutation (c.1691_1693delinsG) in SCNN1B that was responsible for Liddle syndrome in this family. This mutation leads to the substitution of Arg in place of Gln at codon site 564 and generates a new stop codon at 592, influencing the crucial PY motif and resulting in reduced inactivation of the ENaCs. Aside from the proband, eight family members carried the mutation. Intra-familial phenotypic heterogeneity was observed in the blood pressure and serum potassium levels. Amiloride therapy combined with a low sodium diet is effective to alleviate the symptoms of patients with Liddle syndrome. c.1691_1693delinsG, a novel frame-shift mutation in the β subunit of ENaC, was identified in a Chinese family with Liddle syndrome by whole-exome sequencing. Phenotypic heterogeneity can make diagnosis of Liddle syndrome difficult on the basis of clinical or biochemical characteristics alone. Genetic analysis is a useful tool allowing timely and accurate diagnosis of Liddle syndrome and playing a guiding role in precise treatment of the disease.

Liddle syndrome (LS) is a rare autosomal dominant condition secondary to a gain-of-function mutation affecting the epithelial sodium channels (ENaCs) in the distal nephron. It presents with early-onset hypertension, hypokalemia, and metabolic alkalosis in the face of hyporeninemia and hypoaldosteronism. We report a novel mutation affecting the ENaCs in a normotensive adolescent with LS. We describe a pediatric case of LS with a novel mutation and review the condition's presentation and management. To date, 31 different mutations in the β- or γ-subunit of ENaCs have been reported as associated with LS. We describe a 16-year-old girl presenting with muscle cramps with a strong family history of hypertension and hypokalemia. Initial investigations revealed hypokalemia together with hypoaldosteronism and hyporeninemia. Subsequent genetic testing revealed a novel mutation in SCNN1B (deletion: c.1713delC), leading to the premature termination of the sodium channel epithelial 1 subunit-β protein and the LS phenotype. Treatment with triamterene (50 mg, twice daily) and potassium chloride (20 mEq, once daily) normalized the serum potassium and led to resolution of her muscle cramps. It is essential to consider investigating the presence of rare genetic syndromes, like LS, when a patient presents with hypokalemia. Further studies are needed to understand the variable presentation of this condition.

Liddle's syndrome is a rare monogenic form of hypertension caused by truncating or missense mutations in the C termini of the epithelial sodium channel (ENaC) β or γ subunits. Patients with this syndrome present with early onset of hypertension, hypokalemia, metabolic alkalosis, hyporeninemia and hypoaldosteronism, and a potassium-sparing diuretics (triamterene or amiloride) can drastically improves the disease condition. Although elderly patients having these characteristics were considered to have Liddle's syndrome or Liddle's-like syndrome, no previous report has indicated that Liddle's-like syndrome could be caused by nephrotic syndrome of primary glomerular disease, which is characterized by urinary excretion of > 3 g of protein/day plus edema and hypoalbuminemia, or has explained how the activity function of ENaC could be affected in the setting of high proteinuria. A 65-year-old Japanese man presented with nephrotic syndrome. He had no remarkable family history, but had a medical history of hypertension and hyperlipidemia. On admission, hypertension, spironolactone-resistant hypokalemia (2.43 mEq/l), hyporeninemic hypoaldosteronism, and metabolic alkalosis, which suggested Liddle's syndrome, were observed. Treatment with triamterene together with a steroid for nephrotic syndrome resulted in rapid and remarkable effective on improvements of hypertension, hypokalemia, and edema of the lower extremities. Renal biopsy revealed membranous nephropathy (MN) as the cause of nephrotic syndrome, and advanced gastric cancer was identified on screening examination for cancers that could be associated with the development of MN. After total gastrectomy, triamterene was not required and proteinuria decreased. A mutation in the β or γ subunits of the ENaC gene was not identified. We reported for the first time a case of Liddle's-like syndrome associated with nephrotic syndrome secondary to MN. Aberrant activation of ENaC was suggested transient during the period of high proteinuria, and the activation was reversible with a decrease in proteinuria.