Integrating population variation and protein structural analysis to improve the clinical genetic diagnosis and treatment in children with congenital nephrogenic diabetes insipidus

Abstract Background and Objectives: Congenital nephrogenic diabetes insipidus (NDI) is a rare genetic disorder characterized by renal inability to concentrate urine. Establishing the genetic diagnosis appears particularly important to NDI for early detection and differential diagnosis.Method: We utilized a Chinese multicenter registry to investigate genotype and phenotype in children with NDI from 2014 to 2019. The structural locations of the pathogenic mutations from this study and the literature, as well as population variants retried from gnomAD were analyzed. Results: A total of 10 boys from 9 families carried mutations in AVPR2 (8/10) or AQP2 (2/10). Another 7 relatives of the families were diagnosed by sequencing for partial or subclinical NDI. Patients presented with dehydration, polyuria-polydipsia, and severe hypernatremia with a median age at diagnosis of 1.0 month (IQR 0.16, 18). Protein structural analysis revealed a notable clustering of diagnostic mutations in the transmembrane regions of AVPR2, and enrichment of diagnostic mutations by autosomal dominant inheritance (AD) in the C terminal region of AQP2. The pathogenic mutations are significantly more likely to be buried inside the domain comparing the population variants. Through structural analysis and in silico prediction, the eight mutations identified in this study were considered as presumably disease causative. The most common treatments were thiazide diuretics and non-steroidal anti-inflammatory drugs (NSAIDs). Emergency treatment of hypernatremic dehydration in neonates should not choose the isotonic saline as a rehydration fluid.Conclusion: Genetic analysis presumably confirmed the diagnosis of NDI in every patient of the studied cohort. A plea of early identifying NDI confirmed by phenotype and genotype, and consequently optimize the treatment.