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PKD2 mutation in an Iranian autosomal dominant polycystic kidney disease family with misleading linkage analysis data.

ABSTRACT: BACKGROUND:Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disorder caused by mutation in 2 genes PKD1 and PKD2. Thus far, no mutation is identified in approximately 10% of ADPKD families, which can suggest further locus heterogeneity. Owing to the complexity of direct mutation detection, linkage analysis can initially identify the responsible gene in appropriate affected families. Here, we evaluated an Iranian ADPKD family apparently unlinked to both PKD1 and PKD2 genes. This is one of the pioneer studies in genetic analysis of ADPKD in Iranian population. METHODS:Linkage reanalysis was performed by regenotyping of flanking microsatellite markers in 8 individuals of the ADPKD family. Direct mutation analysis was performed by Sanger sequencing. RESULTS:Mutation analysis revealed a pathogenic mutation (c.1094+1G>A) in the PKD2 gene in the proband. Analyzing 2 healthy and 4 clinically affected members confirmed the correct segregation of the mutation within the family and also ruled out the disease in 1 suspected individual. Misinterpretation of the linkage data was due to the occurrence of 1 crossing over between the PKD2 intragenic and the nearest downstream marker (D4S2929). Homozygosity of upstream markers caused the recombination indistinguishable. CONCLUSION:Although analysis of additive informative polymorphic markers can overcome the misleading haplotype data, it is limited because of the lack of other highly polymorphic microsatellite markers closer to the gene. Direct mutation screening can identify the causative mutation in the apparently unlinked pedigree; moreover, it is the only approach to achieve the confirmed diagnosis in individuals with equivocal imaging results.

SUBMITTER: Entezam M

PROVIDER: S-EPMC4919558 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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PKD2 mutation in an Iranian autosomal dominant polycystic kidney disease family with misleading linkage analysis data.

Entezam Mona M Khatami Mohammad Reza MR Saddadi Fereshteh F Ayati Mohsen M Roozbeh Jamshid J Keramatipour Mohammad M

Kidney research and clinical practice 20160227 2

<h4>Background</h4>Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disorder caused by mutation in 2 genes PKD1 and PKD2. Thus far, no mutation is identified in approximately 10% of ADPKD families, which can suggest further locus heterogeneity. Owing to the complexity of direct mutation detection, linkage analysis can initially identify the responsible gene in appropriate affected families. Here, we evaluated an Iranian ADPKD family apparently unlinked to bot ...[more]

PMID: 27366664

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Project description:BACKGROUND:PKD2-related autosomal dominant polycystic kidney disease (ADPKD) is widely acknowledged to be of milder severity than PKD1-related disease, but population-based studies depicting the exact burden of the disease are lacking. We aimed to revisit PKD2 prevalence, clinical presentation, mutation spectrum, and prognosis through the Genkyst cohort. STUDY DESIGN:Case series, January 2010 to March 2016. SETTINGS & PARTICIPANTS:Genkyst study participants are individuals older than 18 years from 22 nephrology centers from western France with a diagnosis of ADPKD based on Pei criteria or at least 10 bilateral kidney cysts in the absence of a familial history. Publicly available whole-exome sequencing data from the ExAC database were used to provide an estimate of the genetic prevalence of the disease. OUTCOMES:Molecular analysis of PKD1 and PKD2 genes. Renal survival, age- and sex-adjusted estimated glomerular filtration rate. RESULTS:The Genkyst cohort included 293 patients with PKD2 mutations (203 pedigrees). PKD2 patients with a nephrology follow-up corresponded to 0.63 (95% CI, 0.54-0.72)/10,000 in Brittany, while PKD2 genetic prevalence was calculated at 1.64 (95% CI, 1.10-3.51)/10,000 inhabitants in the European population. Median age at diagnosis was 42 years. Flank pain was reported in 38.9%; macroscopic hematuria, in 31.1%; and cyst infections, in 15.3% of patients. At age 60 years, the cumulative probability of end-stage renal disease (ESRD) was 9.8% (95% CI, 5.2%-14.4%), whereas the probability of hypertension was 75.2% (95% CI, 68.5%-81.9%). Although there was no sex influence on renal survival, men had lower kidney function than women. Nontruncating mutations (n=36) were associated with higher age-adjusted estimated glomerular filtration rates. Among the 18 patients with more severe outcomes (ESRD before age 60), 44% had associated conditions or nephropathies likely to account for the early progression to ESRD. LIMITATIONS:Younger patients and patients presenting with milder forms of PKD2-related disease may not be diagnosed or referred to nephrology centers. CONCLUSIONS:Patients with PKD2-related ADPKD typically present with mild disease. In case of accelerated degradation of kidney function, a concomitant nephropathy should be ruled out.

Project description:Purpose To define the magnetic resonance (MR) imaging prevalence of pancreatic cysts in a cohort of patients with autosomal dominant polycystic kidney disease (ADPKD) compared with a control group without ADPKD that was matched for age, sex, and renal function. Materials and Methods In this HIPAA-compliant, institutional review board-approved study, all patients with ADPKD provided informed consent; for control subjects, informed consent was waived. Patients with ADPKD (n = 110) with mutations identified in PKD1 or PKD2 and control subjects without ADPKD or known pancreatic disease (n = 110) who were matched for age, sex, estimated glomerular filtration rate, and date of MR imaging examination were evaluated for pancreatic cysts by using axial and coronal single-shot fast spin-echo T2-weighted images obtained at 1.5 T. Total kidney volume and liver volume were measured. Univariate and multivariable logistic regression analyses were conducted to evaluate potential associations between collected variables and presence of pancreatic cysts among patients with ADPKD. The number, size, location, and imaging characteristics of the cysts were recorded. Results Patients with ADPKD were significantly more likely than control subjects to have at least one pancreatic cyst (40 of 110 patients [36%] vs 25 of 110 control subjects [23%]; P = .027). In a univariate analysis, pancreatic cysts were more prevalent in patients with ADPKD with mutations in PKD2 than in PKD1 (21 of 34 patients [62%] vs 19 of 76 patients [25%]; P = .0002). In a multivariable logistic regression model, PKD2 mutation locus was significantly associated with the presence of pancreatic cysts (P = .0004) and with liver volume (P = .038). Patients with ADPKD and a pancreatic cyst were 5.9 times more likely to have a PKD2 mutation than a PKD1 mutation after adjusting for age, race, sex, estimated glomerular filtration rate, liver volume, and total kidney volume. Conclusion Pancreatic cysts were more prevalent in patients with ADPKD with PKD2 mutation than in control subjects or patients with PKD1 mutation. (©) RSNA, 2016 Online supplemental material is available for this article.

Project description:BACKGROUND:Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder, leading to end stage renal failure and kidney transplantation in its most serious form. The severity of the disease's manifestation depends on the genetic determination of ADPKD. The huge variability of different phenotypes (even within a single family) is not only modulated by the two main ADPKD genes (PKD1 and PKD2) but also by modifier genes and the whole genetic background. CASE PRESENTATION:This is a report of an ADPKD family with co-inheritance of PKD1 and PKD2 pathogenic variants. The proband, with an extremely serious manifestation of ADPKD (the man was diagnosed in early childhood, and with end stage renal disease aged 23), underwent genetic analysis of PKD1 and PKD2, which revealed the presence of pathogenic mutations in both of these genes. The missense PKD2 mutation p.Arg420Gly came from the proband's father, with a mild ADPKD phenotype. The same mutation of the PKD2 gene and similar mild disease presentation were found in the proband's aunt (father's sister) and her son. The nonsense mutation p.Gln2196* within the PKD1 gene was probably inherited from the proband's mother, who died at the age of 45. It was only discovered post mortem, that the real cause of her death was kidney failure as a consequence of untreated ADPKD. Unfortunately, neither the DNA of the proband's mother nor the DNA of any other family members from this side of the pedigree were available for further examination. The proband underwent successful cadaveric kidney transplantation at the age of 24, and this replacement therapy lasted for the next 15 years. CONCLUSIONS:Here, we present a first case of bilineal ADPKD inheritance in the Czech Republic. This report highlights the significant role of modifier genes in genetic determination of ADPKD, especially in connection with seriously deteriorated disease phenotypes. In our case, the modifying role is probably mediated by the PKD2 gene.

Dataset Information

PKD2 mutation in an Iranian autosomal dominant polycystic kidney disease family with misleading linkage analysis data.

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PKD2 mutation in an Iranian autosomal dominant polycystic kidney disease family with misleading linkage analysis data.

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