Phenotypic Variability in Siblings with Autosomal Recessive Polycystic Kidney Disease

Next generation sequencing identifies WNT signalling as a significant pathway in Autosomal Recessive Polycystic Kidney Disease (ARPKD) manifestation and may be linked to disease severity

INTRODUCTION

Autosomal Recessive Polycystic Kidney Disease (ARPKD) is a rare paediatric disease primarily caused by sequence variants in PKHD1. ARPKD presents with considerable clinical variability relating to the type of PKHD1 sequence variant, but not its position. Animal models of Polycystic Kidney Disease (PKD) suggest a complex genetic landscape, with genetic modifiers as a potential cause of disease variability.

METHODS

To investigate in an unbiased manner the molecular mechanisms of ARPKD and identify potential indicators of disease severity, Whole Exome Sequencing (WES) and RNA-Sequencing (RNA-Seq) were employed on human ARPKD kidneys and age-matched healthy controls.

RESULTS

WES confirmed the clinical diagnosis of ARPKD in our patient cohort consisting of ten ARPKD kidneys. Sequence variant type, nor position of PKHD1 sequence variants, was linked to disease severity. Sequence variants in genes associated with other ciliopathies were detected in the ARPKD cohort, but only PKD1 could be linked to disease severity. Transcriptomic analysis on a subset of four ARPKD kidneys representing severe and moderate ARPKD, identified a significant number of genes relating to WNT signalling, cellular metabolism and development. Increased expression of WNT signalling-related genes was validated by RT-qPCR in severe and moderate ARPKD kidneys. Two individuals in our cohort with the same PKHD1 sequence variants but different rates of kidney disease progression, with displayed transcriptomic differences in the expression of WNT signalling genes.

CONCLUSION

ARPKD kidney transcriptomics highlights changes in WNT signalling as potentially significant in ARPKD manifestation and severity, providing indicators for slowing down the progression of ARPKD.

Epidemiology and outcomes of pediatric autosomal recessive polycystic kidney disease in the Middle East and North Africa

The incidence of rare diseases is expected to be comparatively higher in the Middle East and North Africa (MENA) region than in other parts of the world, attributed to the high prevalence of consanguinity. Most MENA countries share social and economic statuses, cultural relativism, religious beliefs, and healthcare policies. Polycystic kidney diseases (PKDs) are the most common genetic causes of kidney failure, accounting for nearly 8.0% of dialysis cases. The development of PKDs is linked to variants in several genes, including PKD1, PKD2, PKHD1, DZIP1L, and CYS1. Autosomal recessive PKD (ARPKD) is the less common yet aggressive form of PKD. ARPKD has an estimated incidence between 1:10,000 and 1:40,000. Most patients with ARPKD require kidney replacement therapy earlier than patients with autosomal dominant polycystic kidney disease (ADPKD), often in their early years of life. This review gathered data from published research studies and reviews of ARPKD, highlighting the epidemiology, phenotypic presentation, investigations, genetic analysis, outcomes, and management. Although limited data are available, the published literature suggests that the incidence of ARPKD may be higher in the MENA region due to consanguineous marriages. Patients with ARPKD from the MENA region usually present at a later disease stage and have a relatively short time to progress to kidney failure. Limited data are available regarding the management practice in the region, which warrants further investigations.

Novel splice site and nonsense variants in PKHD1 cause autosomal recessive polycystic kidney disease in a Chinese Zhuang ethnic family

BACKGROUND

This study aims to report the clinical characteristics of a child with autosomal recessive polycystic kidney disease (ARPKD) within a Chinese Zhuang ethnic family.

METHODS

We used whole exome sequencing (WES) in the family to examine the genetic cause of the disease. Candidate pathogenic variants were validated by Sanger sequencing.

RESULTS

We identified previously unreported mutations in the PKHD1 gene of the proband with ARPKD through WES: a splice site mutation c.6809-2A > T, a nonsense mutation c.4192C > T(p.Gln1398Ter), and a missense mutation c.2181T > G(p.Asn727Lys). Her mother is a heterozygous carrier of c.2181T > G(p.Asn727Lys) mutation. Her father is a carrier of c.6809-2A > T mutation and c.4192C > T(p.Gln1398Ter) mutation.

CONCLUSIONS

The identification of novel mutations in the PKHD1 gene through WES not only expands the spectrum of known variants but also potentially enhances genetic counseling and prenatal diagnostic approaches for families affected by ARPKD.

A decision-making framework for genomic testing in paediatric nephrology

AIM

Technological advances and increased access have led to genomics expanding beyond the genetics clinic. Consequently, nephrologists can now order genomic testing for their patients. Consistent decision-making around patient and test selection is required to ensure equitable access while maximising the utility of genomic testing. However, there are currently no frameworks to guide decision-making for testing in this context. We aimed to develop an ethical decision-making framework for genomic testing in paediatric nephrology.

METHODS

A three-stage approach was used: (i) review of the literature on decision-making for genomic testing in nephrology and other disciplines; (ii) ethnographic observation of approaches to genomic testing in the general nephrology and renal genetics clinics at an Australian paediatric hospital; (iii) review and revision of the framework with key stakeholders, including clinical geneticists, genetic counsellors, paediatric nephrologists and families from the renal genetics service. The initial framework was modified until consensus from key stakeholders was reached.

RESULTS

A decision-making framework was created with questions designed to explore the impact of genomic testing on patient management, clinical validity, patient characteristics, alternatives to genomic testing, genetic counselling, resource availability, implications for family members, psychosocial considerations, patient autonomy, research, support services and insurance. Case studies were developed to demonstrate the framework's application.

CONCLUSIONS

This framework was designed to guide decisions around patient selection for genomic testing in nephrology in the Australian health-care setting, with potential utility in other institutions and medical disciplines. It may help facilitate consistent approaches to genomic testing, to maximise equity and utility.

Autosomal Recessive Polycystic Kidney Disease: Diagnosis, Prognosis, and Management

Autosomal recessive polycystic kidney disease (ARPKD) is the rare and usually early-onset form of polycystic kidney disease with a typical clinical presentation of enlarged cystic kidneys and liver involvement with congenital hepatic fibrosis or Caroli syndrome. ARPKD remains a clinical challenge in pediatrics, frequently requiring continuous and long-term multidisciplinary treatment. In this review, we aim to give an overview over clinical aspects of ARPKD and recent developments in our understanding of disease progression, risk patterns, and treatment of ARPKD.