Clinical and genetic characteristics of autosomal recessive polycystic kidney disease in Oman

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.

Phenotypic Discordance among Siblings with Autosomal Recessive Polycystic Kidney Disease: Case Report and Review of the Literature

Missense variants in the PKHD1 gene are associated with the full spectrum of autosomal recessive polycystic kidney disease severity and exhibit variable expressivity. The study of clinical expressivity is limited by the extensive allelic heterogeneity within the PKHD1 gene, which encodes a 4074-amino-acid protein. We report the case of adult siblings with biallelic missense PKHD1 variants, c.4870C>T (p.Arg1624Trp) and c.8206T>G (p.Trp2736Gly), who presented with discordant phenotypes. Patient A developed progressive chronic kidney disease and Caroli syndrome in childhood requiring combined liver and kidney transplantation, while patient B remains minimally affected in the fourth decade of life with normal kidney function and signs of medullary sponge kidney on imaging. We review previously reported cases of phenotypic discordance among siblings and suggest that genotypes composed of at least one hypomorphic missense variant are more likely to lead to phenotypic discordance.

Genetic landscape and clinical outcomes of autosomal recessive polycystic kidney disease in Kuwait

Background

Autosomal recessive polycystic kidney disease (ARPKD), a rare genetic disorder characterized by kidney cysts, shows complex clinical and genetic heterogeneity. This study aimed to explore the genetic landscape of ARPKD in Kuwait and examine the intricate relationship between its genes and clinical presentation to enhance our understanding and contribute towards more efficient management strategies for ARPKD.

Methods

This study recruited 60 individuals with suspected ARPKD from 44 different families in Kuwait. The participants were of different ethnicities and aged 0-70 years. Additionally, 33 were male, 15 were female, and 12 had indeterminant sex due to congenital anomalies. Comprehensive clinical data were collected. Mutations were identified by next-generation whole exome sequencing and confirmed using Sanger sequencing.

Results

Of the 60 suspected ARPKD cases, 20 (33.3 %) died within hours of birth or by the end of the first month of life and one (1.7 %) within 12 months of birth. The remaining 39 (65.0 %) cases were alive, at the time of the study, and exhibited diverse clinical features related to ARPKD, including systematic hypertension (5.0 %), pulmonary hypoplasia (11.7 %), dysmorphic features (40.0 %), cardiac problems (8.3 %), cystic liver (5.0 %), Potter syndrome (13.3 %), developmental delay (8.3 %), and enlarged cystic kidneys (100 %). Twelve mutations, including novel truncating mutations, were identified in 31/60 cases (51.7 %) from 17/44 families (38.6 %). Additionally, 8/12 (66.7 %) mutations were in the PKHD1 gene, with the remaining four in different genes: NPHP3, VPS13P, CC2D2A, and ZNF423.

Conclusions

This study highlights the spectrum of clinical features and genetic mutations of patients with ARPKD in Kuwait. It highlights the necessity for personalized approaches to improve ARPKD diagnosis and treatment, offering crucial insights into managing ARPKD.

Simultaneous Pancreatic and Kidney Transplant in Adult with Autosomal Dominant Polycystic Kidney Disease and Type I Diabetes Mellitus: Post Surgical Events and Genetic Review

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited condition characterized by the growth of multiple bilateral cysts in the kidneys. We describe the case of a 35-year-old male with combined ADPKD and type 1 diabetes mellitus with a strong family history of both. At the age of 32, he developed end-stage kidney disease for which he underwent preemptive simultaneous pancreatic and kidney transplant, which in turn led to multiple perioperative complications. Evaluation of familial clustering of genetic disease is critical in genetic epidemiology and precision medicine as it enables estimation of lifetime disease risk and early assessment as well as detection of the disease among one's siblings.

The genetic spectrum of polycystic kidney disease in children

OBJECTIVE

Autosomal dominant polycystic kidney disease is an inherited kidney disorder with mutations in polycystin-1 or polycystin-2. Autosomal recessive polycystic kidney disease is a severe form of polycystic kidney disease that is characterized by enlarged kidneys and congenital hepatic fibrosis. Mutations at PKHD1 are responsible for all typical forms of autosomal recessive polycystic kidney disease.

METHODS

We evaluated the children diagnosed with polycystic kidney disease between October 2020 and May 2022. The diagnosis was established by family history, ultrasound findings, and/or genetic analysis. The demographic, clinical, and laboratory findings were evaluated retrospectively.

RESULTS

There were 28 children (male/female: 11:17) evaluated in this study. Genetic analysis was performed in all patients (polycystin-1 variants in 13, polycystin-2 variants in 7, and no variants in 8 patients). A total of 18 variants in polycystin-1 and polycystin-2 were identified and 9 (50%) of them were not reported before. A total of eight novel variants were identified as definite pathogenic or likely pathogenic mutations. There was no variant detected in the PKDH1 gene.

CONCLUSION

Our results highlighted molecular features of Turkish children with polycystic kidney disease and demonstrated novel variations that can be utilized in clinical diagnosis and prognosis.

Biliary sepsis complication with congenital hepatic fibrosis: an unexpected outcome

BACKGROUND

CHF (Congenital hepatic fibrosis) is a rare hereditary disease characterized by periportal fibrosis and ductal plate malformation. Little is known about the clinical presentations and outcome in CHF patients with an extraordinary complication with biliary sepsis. Our case described a 23-year-old female diagnosed as CHF combined with biliary sepsis. Her blood culture was positive for KP (Klebsiella pneumoniae), and with a high level of CA19-9 (> 1200.00 U/ml, ref: <37.00 U/ml). Meanwhile, her imaging examinations showed intrahepatic bile duct dilatation, portal hypertension, splenomegaly, and renal cysts. Liver pathology revealed periportal fibrosis and irregularly shaped proliferating bile ducts. Whole-exome sequencing identified two heterozygous missense variants c.3860T > G (p. V1287G) and c.9059T > C (p. L3020P) in PKHD1 gene. After biliary sepsis relieved, her liver function test was normal, and imaging examination results showed no significant difference with the results harvested during her biliary sepsis occurred.

CONCLUSION

The diagnosis of CHF complicated with biliary sepsis in the patient was made. Severely biliary sepsis due to KP infection may not inevitably aggravate congential liver abnormality in young patients. Our case provides a good reference for timely treatment of CHF patients with biliary sepsis.

Prospect of genetic disorders in Saudi Arabia

Introduction: Rare diseases (RDs) create a massive burden for governments and families because sufferers of these diseases are required to undergo long-term treatment or rehabilitation to maintain a normal life. In Saudi Arabia (SA), the prevalence of RDs is high as a result of cultural and socio-economic factors. This study, however, aims to shed light on the genetic component of the prevalence of RDs in SA. Methodology: A retrospective study was conducted between September 2020 and December 2021 at King Saud Medical City, a tertiary hospital of the Ministry of Health (MOH), SA. A total of 1080 individuals with 544 potentially relevant variants were included. The index was 738, and the samples were tested in a commercialized laboratory using different molecular techniques, including next-generation sequencing. Result: A total of 867 molecular genetics tests were conducted on 738 probands. These tests included 610 exome sequencing (ES) tests, four genome sequencing (GS) tests, 82 molecular panels, 106 single nucleotide polymorphism (SNP) array, four methylation studies, 58 single-gene studies and three mitochondrial genome sequencing tests. The diagnostic yield among molecular genetics studies was 41.8% in ES, 24% in panels, 12% in SNP array and 24% in single gene studies. The majority of the identified potential variants (68%) were single nucleotide variants (SNV). Other ascertained variants included frameshift (11%), deletion (10%), duplication (5%), splicing (9%), in-frame deletion (3%) and indels (1%). The rate of positive consanguinity was 56%, and the autosomal recessive accounted for 54%. We found a significant correlation between the ES detection rate and positive consanguinity. We illustrated the presence of rare treatable conditions in DNAJC12, SLC19A3, and ALDH7A1, and the presence of the founder effect variant in SKIC2. Neurodevelopmental disorders were the main phenotype for which genetics studies were required (35.7%). Conclusion: This is the sixth-largest local study reporting next-generation sequencing. The results indicate the influence of consanguineous marriages on genetic disease and the burden it causes for the Kingdom of SA. This study highlights the need to enrich our society's knowledge of genetic disorders. We recommend utilising ES as a first-tier test to establish genetic diagnosis in a highly consanguineous population.

Genetic analysis and outcomes of Omani children with steroid-resistant nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is one of the most common kidney disorders seen by pediatric nephrologists and is defined by the presence of heavy proteinuria (>3.5 g/24 h), hypoalbuminemia (<3.5 g/dL), edema, and hyperlipidemia. Most children with NS are steroid-responsive and have a good prognosis following treatment with prednisolone. However, 10%-20% of them have steroid-resistant nephrotic syndrome (SRNS) and fail to respond to treatment. A significant proportion of these children progress to kidney failure.

METHODS

This retrospective study aimed to determine the underlying genetic causes of SRNS among Omani children below 13 years old, over a 15-year period and included 77 children from 50 different families. We used targeted Sanger sequencing combined with next-generation sequencing approaches to perform molecular diagnostics.

RESULTS

We found a high rate of underlying genetic causes of SRNS in 61 (79.2%) children with pathogenic variants in the associated genes. Most of these genetically solved SRNS patients were born to consanguineous parents and variants were in the homozygous state. Pathogenic variants in NPHS2 were the most common cause of SRNS in our study seen in 37 (48.05%) cases. Pathogenic variants in NPHS1 were also seen in 16 cases, especially in infants with congenital nephrotic syndrome (CNS). Other genetic causes identified included pathogenic variants in LAMB2, PLCE1, MYO1E, and NUP93.

CONCLUSION

NPHS2 and NPHS1 genetic variants were the most common inherited causes of SRNS in Omani children. However, patients with variants in several other SRNS causative genes were also identified. We recommend screening for all genes responsible for SRNS in all children who present with this phenotype, which will assist in clinical management decisions and genetic counseling for the affected families.

Review of genetic testing in kidney disease patients: Diagnostic yield of single nucleotide variants and copy number variations evaluated across and within kidney phenotype groups

Genetic kidney disease comprises a diverse group of disorders. These can roughly be divided in the phenotype groups congenital anomalies of the kidney and urinary tract, ciliopathies, glomerulopathies, stone disorders, tubulointerstitial kidney disease, and tubulopathies. Many etiologies can lead to chronic kidney disease that can progress to end-stage kidney disease. Despite each individual disease being rare, together these genetic disorders account for a large proportion of kidney disease cases. With the introduction of massively parallel sequencing, genetic testing has become more accessible, but a comprehensive analysis of the diagnostic yield is lacking. This review gives an overview of the diagnostic yield of genetic testing across and within the full range of kidney disease phenotypes through a systematic literature search that resulted in 115 included articles. Patient, test, and cohort characteristics that can influence the diagnostic yield are highlighted. Detection of copy number variations and their contribution to the diagnostic yield is described for all phenotype groups. Also, the impact of a genetic diagnosis for a patient and family members, which can be diagnostic, therapeutic, and prognostic, is shown through the included articles. This review will allow clinicians to estimate an a priori probability of finding a genetic cause for the kidney disease in their patients.

The genetics of Autosomal Recessive Polycystic Kidney Disease (ARPKD)

ARPKD is a genetically inherited kidney disease that manifests by bilateral enlargement of cystic kidneys and liver fibrosis. It shows a range of severity, with 30% of individuals dying early on and the majority having good prognosis if they survive the first year of life. The reasons for this variability remain unclear. Two genes have been shown to cause ARPKD when mutated, PKHD1, mutations in which lead to most of ARPKD cases and DZIP1L, which is associated with moderate ARPKD. This mini review will explore the genetics of ARPKD and discuss potential genetic modifiers and phenocopies that could affect diagnosis.

Molecular genetics of renal ciliopathies

Renal ciliopathies are a heterogenous group of inherited disorders leading to an array of phenotypes that include cystic kidney disease and renal interstitial fibrosis leading to progressive chronic kidney disease and end-stage kidney disease. The renal tubules are lined with epithelial cells that possess primary cilia that project into the lumen and act as sensory and signalling organelles. Mutations in genes encoding ciliary proteins involved in the structure and function of primary cilia cause ciliopathy syndromes and affect many organ systems including the kidney. Recognised disease phenotypes associated with primary ciliopathies that have a strong renal component include autosomal dominant and recessive polycystic kidney disease and their various mimics, including atypical polycystic kidney disease and nephronophthisis. The molecular investigation of inherited renal ciliopathies often allows a precise diagnosis to be reached where renal histology and other investigations have been unhelpful and can help in determining kidney prognosis. With increasing molecular insights, it is now apparent that renal ciliopathies form a continuum of clinical phenotypes with disease entities that have been classically described as dominant or recessive at both extremes of the spectrum. Gene-dosage effects, hypomorphic alleles, modifier genes and digenic inheritance further contribute to the genetic complexity of these disorders. This review will focus on recent molecular genetic advances in the renal ciliopathy field with a focus on cystic kidney disease phenotypes and the genotypes that lead to them. We discuss recent novel insights into underlying disease mechanisms of renal ciliopathies that might be amenable to therapeutic intervention.