Reverse Phenotypes of Patients with Genetically Confirmed Liddle Syndrome

BACKGROUND: Liddle syndrome was initially characterized by hypertension, hypokalemia, metabolic alkalosis, and suppressed plasma renin and aldosterone, resulting from gain-of-function variants in the epithelial Na + channel (ENaC). Efficient treatment with ENaC inhibitors is available, but the phenotypic spectrum of genetically confirmed Liddle syndrome is unknown, and some patients may remain undiagnosed and at risk of inefficient treatment. In this study, we used a reverse phenotyping approach to investigate the Liddle syndrome phenotypic spectrum and genotype-phenotype correlations.

METHODS: Pubmed, Embase, Scopus, and the Human Gene Mutation Database were searched for articles reporting Liddle syndrome variants. The genetic variants were systematically classified to identify patients with genetically confirmed Liddle syndrome. We identified 62 articles describing 45 unique variants within 86 Liddle syndrome families, and phenotypic data were pooled for 268 patients with confirmed Liddle syndrome.

RESULTS: The Liddle syndrome variants localized to exon 13 of SCNN1B and SCNN1G , disrupting the PPPxY motif critical for downregulating ENaC activity. Hypertension sensitive to ENaC inhibition was present in 97% of adults carrying Liddle syndrome variants while hypokalemia, metabolic alkalosis, and plasma renin and aldosterone suppression showed incomplete penetrance. In addition, 95% and 55% of patients had a family history of hypertension or cerebrovascular events, respectively. The genotype had minor phenotypic effects; however, probands compared with relatives showed significant phenotypic discrepancies consistent with selection bias for initial genetic screening.

CONCLUSIONS: Patients with genetically confirmed Liddle syndrome displayed a phenotypic spectrum, with ENaC-sensitive hypertension and family history of hypertension being the most common features. The phenotype seemed independent of the specific gene or variant type involved.