Heterozygous mutations in the gene that encodes the transcription factor hepatocyte nuclear factor 1β (HNF1B) represent the most common known monogenic cause of developmental kidney disease. Renal cysts are the most frequently detected feature of HNF1B-associated kidney disease; however, other structural abnormalities, including single kidneys and renal hypoplasia, and electrolyte abnormalities can also occur. Extra-renal phenotypes might also be observed; consequently, HNF1B-associated disease is considered a multi-system disorder. Other clinical features include early-onset diabetes mellitus, pancreatic hypoplasia, genital tract malformations, abnormal liver function and early-onset gout. Heterozygous mutations in the coding region or splice sites of HNF1B, and complete gene deletion, each account for ∼50% of all cases of HNF1B-associated disease, respectively, and often arise spontaneously. There is no clear genotype-phenotype correlation, consistent with haploinsufficiency as the disease mechanism. Data from animal models suggest that HNF1B has an important function during several stages of nephrogenesis; however, the precise signalling pathways remain to be elucidated. This Review discusses the genetics and molecular pathways that lead to disease development, summarizes the reported renal and extra-renal phenotypes, and identifies areas for future research in HNF1B-associated disease.

IntroductionYoung adults fare worse than younger adolescents or older adults on a broad range of health indicators. Those with a chronic illness such as renal failure are a particularly vulnerable group, who experience poor outcomes compared with both children and older adults. Understanding how being in receipt of renal replacement therapy (RRT) affects the lives of young adults might help us to better prepare and support these individuals for and on RRT, and improve outcomes. This study aimed to synthesise research describing young adults’ experiences of the psychosocial impact of kidney failure and RRT.DesignA systematic literature review identified qualitative research reporting the perspectives of people aged 16–30 years receiving RRT on the psychosocial impact of renal failure. Electronic databases (including Medline/EMBASE/PsycINFO/ASSIA) were searched to November 2017 for full-text papers. The transparency of reporting of each study was assessed using the Consolidated Criteria for Reporting Qualitative Health Research (COREQ) framework. Quality was assessed using the Critical Appraisal Skills Programme qualitative checklist. An inductive thematic synthesis was undertaken.ParticipantsSeven studies from five different countries were included, comprising 123 young adults receiving RRT.ResultsComprehensiveness of reporting was variable: studies reported 9–22 of the 32 COREQ-checklist items.Three global themes about the impact of kidney failure on young adults were identified: (1) difference desiring normality, (2) thwarted or moderated dreams and ambitions, and (3) uncertainty and liminality. These reflected five organising themes: (1) physical appearance and body image, (2) activity and participation, (3) educational disruption and underachievement, (4) career ambitions and employment difficulties, and (5) social isolation and intimate relationships.ConclusionsAcross different countries and different healthcare settings, young adults on RRT experience difference and liminality, even after transplantation. Tailored social and psychological support is required to allow young adults to experience wellness while in receipt of RRT, and not have life on hold.

Heterozygous mutations of the HNF1B gene are the commonest known monogenic cause of developmental kidney disease. Half of patients have a deletion (approximately 1.3 Mb) of chromosome 17q12, encompassing HNF1B plus 14 additional genes. This 17q12 deletion has been linked with an increased risk of neurodevelopmental disorders, such as autism. Here we compared the neurodevelopmental phenotype of 38 patients with HNF1B-associated renal disease due to an intragenic mutation in 18 patients or due to 17q12 deletion in 20 patients to determine whether haploinsufficiency of HNF1B is responsible for the neurodevelopmental phenotype. Significantly, brief behavioral screening in children with the deletion showed high levels of psychopathology and its impact. Eight individuals (40%) with a deletion had a clinical diagnosis of a neurodevelopmental disorder compared to none with an intragenic mutation. The 17q12 deletions were also associated with more autistic traits. Two independent clinical geneticists were able to predict the presence of a deletion with a sensitivity of 83% and specificity of 79% when assessing facial dysmorphic features as a whole. Thus, the 17q12 deletions but not HNF1B intragenic mutations are associated with neurodevelopmental disorders. Hence, the HNF1B gene is not involved in the neurodevelopmental phenotype of these patients. Nephrologists need to be aware of this association to ensure appropriate referral to psychiatric services.