A Novel <scp> <i>NR3C1</i> </scp> Frameshift Variant Associated With Familial Glucocorticoid Resistance Syndrome: An Integrated Analysis of Steroid Profiling and Structural Modeling

Glucocorticoid resistance syndrome (GRS) is a rare hereditary disorder caused by pathogenic variants in NR3C1, characterized by marked phenotypic heterogeneity and frequent misdiagnosis as primary aldosteronism or subclinical Cushing's syndrome. We report a family harboring a novel NR3C1 frameshift variant and provide an integrated characterization of its clinical and biochemical features. By combining structural prediction, tissue- and single-cell-level expression analyses, in silico virtual gene perturbation, and systematic literature review, we evaluated the potential functional impact and clinical relevance of this variant. Comprehensive clinical phenotyping, steroid metabolomic profiling, adrenal CT imaging, and segregation analysis were performed in the proband and his father. AlphaFold3 was used to predict the structures of wild-type and mutant GRα proteins. Variant pathogenicity was assessed following ACMG/AMP criteria. Cross-tissue and single-cell expression patterns of NR3C1 were analyzed, and in silico virtual knockout analysis was performed to generate exploratory hypotheses regarding potentially affected biological pathways. A systematic review was conducted to summarize previously reported GRS cases, their variants, and associated phenotypes. Two affected males across successive generations presented with refractory hypertension without Cushingoid features. Steroid profiling demonstrated mild hypercortisolemia with elevated ACTH, marked increases in 11-deoxycorticosterone and 11-deoxycortisol, suppressed renin, and low-to-normal aldosterone, consistent with ACTH-driven accumulation of mineralocorticoid precursors. Sequencing identified a novel NR3C1 frameshift variant, c.923dupG (p.Ala309Serfs*6), absent from population databases and co-segregating with the familial phenotype. Structural prediction indicated premature termination within the N-terminal transactivation domain, supporting loss of the downstream DNA-binding and ligand-binding domains. According to ACMG/AMP criteria, the variant was classified as pathogenic. In silico virtual perturbation analysis suggested that NR3C1 dysfunction may extend beyond a linear defect in glucocorticoid signaling, potentially influencing neuroendocrine communication, extracellular matrix regulation, protein translation, and developmental pathways. Literature review identified 66 reported GRS cases encompassing substantial phenotypic variability, with cardiovascular events documented in some carriers of N-terminal or truncating variants. We describe a novel exon 2 NR3C1 frameshift variant that co-segregates with a characteristic GRS hormonal profile and is supported by clinical, genetic, and structural evidence. This case expands the genotype-phenotype spectrum of NR3C1-related GRS. The potential relationship between N-terminal truncating variants and cardiovascular complications remains hypothesis-generating and requires validation in larger cohorts and functional studies. Our findings underscore the importance of considering NR3C1-related GRS in patients presenting with resistant hypertension accompanied by a distinctive steroid profile.