The phenotypic expression of three MSH2 mutations in large Newfoundland families with Lynch syndrome

To compare the phenotypic expression of three different MSH2 mutations causing Lynch syndrome, 290 family members at 50% risk of inheriting a mutation were studied. Two truncating mutations of the MSH2 gene have been identified in Newfoundland: an exon 8 deletion in five families (N=74 carriers) and an exon 4-16 deletion in one family (N=65 carriers). The third mutation was an intron 5 splice site mutation resulting in deletion of exon 5 in RNA and occurred in 12 families (N=151 carriers). Age to onset of first cancer, first colorectal cancer (CRC), first extracolonic cancers and death were compared. By age 60, 89% of family members with the intron 5 mutation, 81% with the exon 8 deletion, and 85% with the exon 4-16 deletion had developed cancer. For all three mutations males had a higher age-related risk of CRC and death compared to females. In the intron 5 splice site mutation carriers, the number of transitional cell cancers of the urinary tract was significantly lower and time to first ovarian cancer was significantly higher than in the carriers of the genomic deletions. The incidence of CRC in MSH2 mutation carriers, exposed to the same environment, is not modified by the specific mutation, although there is a suggestion that type of mutation may influence development of some extracolonic cancers.

Incident renal events and risk factors in autosomal dominant polycystic kidney disease: a population and family-based cohort followed for 22 years

For determination of the incidence of renal events in autosomal dominant polycystic kidney disease (ADPKD) all patients who had ADPKD and attended nephrology/urology clinics in Newfoundland in 1981 were identified, and members of 18 families who were at 50% risk for inheriting ADPKD were followed prospectively for 22 yr, including research clinics at 6-yr intervals. Time to hypertension treatment, stage 3 chronic kidney disease (CKD), ESRD, and death was measured, and the impact of genotype, gender, gender of parent who transmitted PKD, family, family history of essential hypertension, parity, and oral contraceptive pill was assessed. Nine (50%) families had PKD1, four (22%) had PKD2, and one had both PKD1 and PKD2. The number of family members with PKD1 was 136 and with PKD2 was 60. In PKD1 median age to hypertension treatment was 46 yr, to CKD stage 3 was 50 yr, to ESRD was 53 yr, and to death was 67 yr. In PKD2, median age to hypertension treatment was 51 yr, to CKD stage 3 was 66 yr, to death was 71 yr, and ESRD was infrequent. Although the incidence of CKD was later and ESRD occurred infrequently in PKD2 compared with PKD1, early onset of hypertension occurred and life expectancy was compromised. Genotype, family, and proteinuria were identified as risk factors for incident renal events. Gender, gender of parent who transmitted PKD, family history of essential hypertension, multiparity, and use of the oral contraceptive pill were not identified as risk factors for renal events in ADPKD.

High frequency of hereditary colorectal cancer in Newfoundland likely involves novel susceptibility genes

PURPOSE

Newfoundland has one of the highest rates of colorectal cancer in North America. The most common hereditary form of colorectal cancer is hereditary nonpolyposis colorectal cancer caused by mutations in genes involved in mismatch repair. Our purpose was to determine the proportion of hereditary colorectal cancer and to determine the genetic basis of disease in both population and clinically referred cohorts from Newfoundland.

EXPERIMENTAL DESIGN

Seventy-eight colorectal cancer patients were accrued over a 2-year period from the Avalon Peninsula of Newfoundland. We also examined 31 hereditary nonpolyposis colorectal cancer-like families, which had been referred to the Provincial Medical Genetics Program. Tumors from probands were tested by immunohistochemistry for deficiencies in MLH1, MSH2, and MSH6 proteins and tested for DNA microsatellite instability. Mutation analyses of MLH1, MSH2, and MSH6 were undertaken by direct sequencing and an assay to detect deletions, amplifications, and rearrangements in MSH2 and MLH1.

RESULTS

We identified eight population-based families that fulfill the Amsterdam I or II criteria, 4 (50%) of which seem to have hereditary cancer not attributable to the most commonly mutated mismatch repair genes. In addition, in 16 of 21 (76%) referred families fulfilling Amsterdam I or II criteria, no mutations were found in the three most commonly altered mismatch repair genes, and tumor analyses corroborated these findings.

CONCLUSIONS

It seems that strong and novel genetic causes of hereditary colorectal cancer are responsible for a high proportion of colorectal cancer in this population. Conditions are suitable for the identification of these genes by linkage studies of large Newfoundland cancer families.

Long-term care in the St. John's region: impact of single entry and prediction of bed need

In 1996, the St. John's region had a population of 8,435 > or = 75 years, with 996 nursing home (NH) beds and 550 supervised care (SC) beds. A single entry system to these institutions was implemented in 1995. To determine the impact of the single entry system, the demographic and clinical characteristics of NH residents were assessed in 1997 (N = 1,044) and in 2003 (N = 963). To determine the efficiency of placement and the need for long-term care beds, two incident cohorts requesting placement were studied in 1995/96 (N = 467) and in 1999/2000 (N = 464). Degree of disability was determined using the Residents Utilization Groups III classification (RUG-III) and the Alberta Resident Classification Score (ARCS), and time to placement and to death was measured. In prevalent NH residents, the percentage without RUGS-III disability decreased from 18.5% in 1997 and to 9.9% in 2003. The proportion recommended for NH was 75% in 1995/96 and 72% in 1999/2000, despite the fact that the proportion with RUGS-III disability was 64% in both periods. Using a decision tree, optimal placement for the 1999/2000 cohort was 36% to SC, 20% to SC for the cognitively impaired, and 44% to NH. Predicted need for long-term care beds in 2004 matched poorly with current provision of NH and SC beds, and the mismatch will be worse in 2014. It was concluded that the single entry system was associated with improved appropriateness of NH bed utilization. However, there was a mismatch in need for and provision of institutional long-term care. Investment in the reconfiguration of long-term care beds by case mix and by geography is necessary.

The clinical epidemiology of cardiovascular disease in chronic kidney disease

PURPOSE OF REVIEW

To review recent publications concerning the epidemiology and management of cardiovascular disease in the stages of chronic kidney disease.

RECENT FINDINGS

Chronic kidney disease is a state of increased risk for atherosclerotic and cardiomyopathic disease. The mechanisms of cardiovascular disease probably change with the different stages of chronic kidney disease. Both proteinuria and decreased glomerular filtration rate are probably independent cardiovascular disease risk factors, although the impact of the latter is modest. Traditional risk factors are important predictors of cardiovascular disease in chronic kidney disease. Recent randomized controlled trials and cohort studies have supported interventions for smoking cessation, blood pressure control, renin-angiotensin system blockade, the correction of lipid abnormalities, and utilizing antiplatelet agents. Some uraemia-related risk factors predict the development of cardiovascular disease, particularly hypoalbuminaemia, inflammation, anaemia, and homocysteinaemia. However, randomized controlled trials of anaemia correction and of an increased quantity of dialysis were negative.

SUMMARY

The role of oxidant stress, divalent ion abnormalities, various lipid abnormalities and other potential factors require further investigation. To determine whether these uraemia-related factors are markers of cardiovascular disease risk or are actually cardiotoxic requires additional randomized controlled trials.

Congestive Heart Failure in Chronic Kidney Disease: Disease-specific Mechanisms of Systolic and Diastolic Heart Failure and Management

There is a high burden of cardiac disease in the CKD population. Severe LVH, dilated cardiomyopathy, and coronary artery disease occur frequently and result in the manifestations of CHF,which is probably more important with respect to prognosis than symptomatic. Multiple risk factors for CVD include traditional risk factors and those unique to the CKD population. Furthermore, the distinctive aspects of CKD patients sometimes warrant special consideration in making management decisions. Nonetheless, interventions such as controlling hypertension, specific pharmacologic options, lifestyle modification, anemia management, and early nephrology referral are recommended when appropriate.

Double-blind comparison of full and partial anemia correction in incident hemodialysis patients without symptomatic heart disease

It is unclear whether physiologic hemoglobin targets lead to cardiac benefit in incident hemodialysis patients without symptomatic heart disease and left ventricular dilation. In this randomized, double-blind study, lower (9.5 to 11.5 g/dl) and higher (13.5 to 14.5 g/dl) hemoglobin targets were generated with epoetin alpha over 24 wk and maintained for an additional 72 wk. Major eligibility criteria included recent hemodialysis initiation and absence of symptomatic cardiac disease and left ventricular dilation. The primary outcome measure was left ventricular volume index (LVVI). The study enrolled 596 patients. Mean age, duration of dialysis therapy, baseline predialysis hemoglobin, and LVVI were 50.8 yr, 0.8 yr, 11.0 g/dl, and 69 ml/m2, respectively; 18% had diabetic nephropathy. Mean hemoglobin levels in the higher and lower target groups were 13.3 and 10.9 g/dl, respectively, at 24 wk. Percentage changes in LVVI between baseline and last value were similar (7.6% in the higher and 8.3% in the lower target group) as were the changes in left ventricular mass index (16.8 versus 14.2%). For the secondary outcomes, the only between-group difference was an improved SF-36 Vitality score in the higher versus the lower target group (1.21 versus -2.31; P = 0.036). Overall adverse event rates were similar in both target groups; higher (P < 0.05) rates of skeletal pain, surgery, and dizziness were seen in the lower target group, and headache and cerebrovascular events were seen in the higher target group. Normalization of hemoglobin in incident hemodialysis patients does not have a beneficial effect on cardiac structure, compared with partial correction.

Multiple risk factor intervention in chronic kidney disease: management of cardiac disease in chronic kidney disease patients

This article describes the relationship between CVD and CKD, the current state of knowledge regarding medical interventions, and underscores the importance of attending to both CVD and kidney disease aspects in each individual. The burden of cardiac disease in CKD patients is high with severe LVH, dilated cardiomyopathy and coronary artery disease occurring frequently. This predisposes to congestive heart failure, angina, myocardial infarction, and death. Multiple risk factors for cardiac disease exist and include hypertension, diabetes, smoking, anemia, abnormal calcium and phosphate metabolism, inflammation, and LVH. The efficacy of risk factor intervention has not been established in these populations, although there is good evidence for good blood pressure control, partial correction of anemia, treatment of dyslipidemia, cessation of tobacco use, correction of divalent abnormalities, and aspirin us. Appropriate use of ACE inhibitors, beta-blockers, and statins should be encouraged.

Clinical and genetic epidemiology of Bardet-Biedl syndrome in Newfoundland: a 22-year prospective, population-based, cohort study

Bardet-Biedl syndrome (BBS) and Laurence-Moon syndrome (LMS) have a similar phenotype, which includes retinal dystrophy, obesity, and hypogenitalism. They are differentiated by the presence of spasticity and the absence of polydactyly in LMS. The aims of this study were to describe the epidemiology of BBS and LMS, further define the phenotype, and examine genotype-phenotype correlation. The study involved 46 patients (26 males, 20 females) from 26 families, with a median age of 44 years (range 1-68 years). Assessments were performed in 1986, 1993, and 2001 and included neurological assessments, anthropometric measurements, and clinical photographs to assess dysmorphic features. The phenotype was highly variable within and between families. Impaired co-ordination and ataxia occurred in 86% (18/21). Thirty percent (14/46) met criteria for psychiatric illness; other medical problems included cholecystectomy in 37% (17/46) and asthma in 28% (13/46). Dysmorphic features included brachycephaly, large ears, and short, narrow palpebral fissures. There was no apparent correlation of clinical or dysmorphic features with genotype. Two patients were diagnosed clinically as LMS but both had mutations in a BBS gene. The features in this population do not support the notion that BBS and LMS are distinct. The lack of a genotype-phenotype correlation implies that BBS proteins interact and are necessary for the development of many organs.

Rationale--Trial to Reduce Cardiovascular Events with Aranesp Therapy (TREAT): evolving the management of cardiovascular risk in patients with chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) have a high burden of mortality and cardiovascular morbidity. Additional strategies to modulate cardiovascular risk in this population are needed. Data suggest that anemia is a potent and potentially modifiable risk factor for cardiovascular disease in patients with CKD, but these data remain unsubstantiated by any randomized controlled trial (RCT). Furthermore, the clinical practice guidelines for anemia management in patients with CKD are based on limited data. The need for new RCTs to address critical knowledge deficits, particularly with regard to the impact of anemia therapy on cardiovascular disease and survival, is recognized within the guidelines and independent comprehensive reviews of the existing published trial data.

STUDY DESIGN

The Trial to Reduce Cardiovascular Events with Aranesp (Amgen Inc, Thousand Oaks, Calif) (darbepoetin alfa) Therapy (TREAT) is a 4000-patient, multicenter, double-blind RCT, designed to determine the impact of anemia therapy with darbepoetin alfa on mortality and nonfatal cardiovascular events in patients with CKD and type 2 diabetes mellitus. Subjects will be randomized in a 1:1 manner to either darbepoetin alfa therapy to a target hemoglobin (Hb) of 13 g/dL or control, consisting of placebo for Hb > or =9 g/dL or darbepoetin alfa for Hb <9 g/dL until Hb is again Hb > or =9 g/dL. TREAT is event-driven and has a composite primary end point comprising time to mortality and nonfatal cardiovascular events, including myocardial infarction, myocardial ischemia, stroke, and heart failure. TREAT will provide data that are critical to evolution of the management of cardiovascular risk in this high-risk population.

The impact of implantable cardioverter-defibrillator therapy on survival in autosomal-dominant arrhythmogenic right ventricular cardiomyopathy (ARVD5)

OBJECTIVES

We sought to determine the impact of implantable cardioverter-defibrillator (ICD) therapy in patients with familial arrhythmogenic right ventricular cardiomyopathy (ARVC).

BACKGROUND

Arrhythmogenic right ventricular cardiomyopathy is a cause of sudden cardiac death, which may be prevented by ICD.

METHODS

We studied 11 families in which a 3p25 deoxyribonucleic acid (DNA) haplotype at locus ARVD5 segregated with disease and compared mortality in subjects who received an ICD with that in control subjects who were matched for age, gender, ARVC status, and family. Subjects (n = 367) at 50% a priori risk of inheriting ARVC were classified as high risk (HR) (n = 197), low risk (n = 92), or unknown (n = 78) on the basis of clinical events, DNA haplotyping, and/or pedigree position. Forty-eight HR subjects (30 males, [median age 32 years] and 18 females [median age 41 years]) were followed after ICD (secondary to ventricular tachycardia [VT] in 27%). Survival was compared with 58 HR control subjects who were alive at the same age to-the-day at which the ICD subject received the device.

RESULTS

In the HR group, 50% of males were dead by 39 years and females by 71 years: relative risk of death was 5.1 (95% confidence interval 3 to 8.5) for males. The five-year mortality rate after ICD in males was zero compared with 28% in control subjects (p = 0.009). Within five years, the ICD fired for VT in 70% and for VT >240 beats/min in 30%, with no difference in discharge rate when analyzed by ICD indication.

CONCLUSIONS

The unknown mutation at the ARVD5 locus causing ARVC results in high mortality. Risk stratification using genetic haplotyping and ICD therapy produced improved survival for males.

Linkage disequilibrium mapping in the Newfoundland population: a re-evaluation of the refinement of the Bardet?Biedl syndrome 1 critical interval

Genetically isolated populations, such as Newfoundland, have contributed greatly to the identification of disease-causing genes. A linkage disequilibrium (LD) study involving six Newfoundland families predicted a critical interval for Bardet-Biedl syndrome 1 (BBS1) (Young et al. in Am J Hum Genet 65:1680-1687, 1999), but the subsequent identification of BBS1 revealed that it lies outside this region. This suggested that either there is another gene responsible for BBS in these families or the Newfoundland population may not be ideal for LD studies. We screened these six Newfoundland families for mutations in BBS1 and found that affected individuals in five of them were homozygous for the same M390R mutation. There was no evidence for any BBS1 mutation in the affected individual in the sixth family. Therefore, one of the criteria for LD mapping was not met; namely, there should be a single disease-causing allele in the population. Haplotype analysis of unaffected individuals from south-west Newfoundland and English BBS1 patients homozygous for M390R, revealed that a second criterion for LD mapping was violated. The M390R mutation occurred in a common haplotype and both of these chromosomes, the ancestral wild-type and disease-causing haplotypes, were introduced to Newfoundland and spread by a founder effect. Moreover, it was found that disease-associated alleles occurred at relatively high frequencies in normal haplotypes and this probably accounted for the incorrect prediction in the previous LD study. Knowing the amount of genetic variation and its distribution in the Newfoundland population would be useful to maximize its potential for mapping hereditary disorders.

Mutations in a member of the Ras superfamily of small GTP-binding proteins causes Bardet-Biedl syndrome

RAB, ADP-ribosylation factors (ARFs) and ARF-like (ARL) proteins belong to the Ras superfamily of small GTP-binding proteins and are essential for various membrane-associated intracellular trafficking processes. None of the approximately 50 known members of this family are linked to human disease. Using a bioinformatic screen for ciliary genes in combination with mutational analyses, we identified ARL6 as the gene underlying Bardet-Biedl syndrome type 3, a multisystemic disorder characterized by obesity, blindness, polydactyly, renal abnormalities and cognitive impairment. We uncovered four different homozygous substitutions in ARL6 in four unrelated families affected with Bardet-Biedl syndrome, two of which disrupt a threonine residue important for GTP binding and function of several related small GTP-binding proteins. Analysis of the Caenorhabditis elegans ARL6 homolog indicates that it is specifically expressed in ciliated cells, and that, in addition to the postulated cytoplasmic functions of ARL proteins, it undergoes intraflagellar transport. These findings implicate a small GTP-binding protein in ciliary transport and the pathogenesis of a pleiotropic disorder.

Comparative genomics identifies a flagellar and basal body proteome that includes the BBS5 human disease gene

Cilia and flagella are microtubule-based structures nucleated by modified centrioles termed basal bodies. These biochemically complex organelles have more than 250 and 150 polypeptides, respectively. To identify the proteins involved in ciliary and basal body biogenesis and function, we undertook a comparative genomics approach that subtracted the nonflagellated proteome of Arabidopsis from the shared proteome of the ciliated/flagellated organisms Chlamydomonas and human. We identified 688 genes that are present exclusively in organisms with flagella and basal bodies and validated these data through a series of in silico, in vitro, and in vivo studies. We then applied this resource to the study of human ciliation disorders and have identified BBS5, a novel gene for Bardet-Biedl syndrome. We show that this novel protein localizes to basal bodies in mouse and C. elegans, is under the regulatory control of daf-19, and is necessary for the generation of both cilia and flagella.

Need for coronary artery bypass grafting in Newfoundland and Labrador: the impact of increased demand

BACKGROUND

In the past decade, growth of coronary revascularization in Canada has been substantial. It was hypothesized that as coronary angiography (CA) rates increased, referral for necessary coronary artery bypass grafting (CABG) would also increase, and include patients with multivessel disease and class I to III angina who required elective surgery. Furthermore, it was proposed that the number of CABG surgeries needed would increase at a similar rate to that of CA.

METHODS

An incident cohort of patients who received CA in 1998/1999 was identified, and the group referred for CABG was followed. Clinical characteristics, appropriateness and necessity scores using specific criteria, and waiting times were evaluated and compared with a similar cohort from 1994/1995. Utilization data for coronary revascularization procedures from 1994 to 2002 were reviewed.

RESULTS

Between 1994/1995 and 1998/1999, the number of CAs per year increased by 37%. The inappropriateness rate for CA was 4% in 1998/1999. The proportion of patients diagnosed with critical coronary artery disease increased from 68% in 1994/1995 to 74% in 1998/1999. The number referred for CABG increased by 48%, and the number for percutaneous transluminal coronary angioplasty (PTCA) increased by 137%. The increase in the number referred for CABG was attributable to the increase in the number of patients with less severe symptoms who required delayed elective CABG. The necessity rate for CABG in the referred group was 94% in 1994/1995 and 95% in 1998/1999. A further 91 patients were identified who needed CABG but did not receive it, 86% of whom had PTCA. From 1999 to 2002, the annual growth rate in those referred for CABG was higher than the growth rate for CA.

CONCLUSIONS

With the growth in CA, the rate of discovery of high risk coronary anatomy actually increased. Growth in CABG volume was attributable to growth in the need for elective surgery in patients with class I to III angina. The rate of CABG increased disproportionately to the rate of CA, despite higher rates of PTCA with stenting. It is likely that the demand for CABG will continue to rise steadily, as expansion of angiography occurs, and may be higher than expected from the growth in CA.

Bardet–Biedl syndrome 1 genotype and obesity in the Newfoundland population

BACKGROUND AND OBJECTIVES

Obesity is one of the primary clinical features of Bardet-Biedl Syndrome (BBS), a genetically heterogeneous disorder that is usually inherited as an autosomal recessive trait. It has been suggested that heterozygous carriers of BBS are predisposed to obesity. We set out to identify the common mutation in BBS1 families from southwest Newfoundland and to examine the relationship between this mutation and obesity in the general population.

METHODS AND SUBJECTS

We genotyped BBS1 families from Newfoundland to determine the nature of the mutation causing BBS in this population. We then screened 200 obese individuals (average body mass index (BMI)=37.9 kg/m2; average waist to hip ratio=0.935; average waist=113.8 cm) and 200 ethnically matched, unrelated, controls (average BMI=25.0 kg/m2; average waist to hip ratio=0.896; average waist=86.9 cm) from the same geographic region for the presence of this mutation.

RESULTS

All affected members of the six Newfoundland BBS1 families were homozygous for the most common BBS1 mutation (M390R). This mutation was found in the heterozygous state in three of the 200 obese individuals and also in three of the 200 matched controls.

CONCLUSIONS

The high frequency of BBS1 in Newfoundland appears to be the result of a founder event. Our data do not support the hypothesis that the M390R BBS1 mutation plays a significant role in the frequency of obesity in the general public in Newfoundland.

Impact of gender and parent of origin on the phenotypic expression of hereditary nonpolyposis colorectal cancer in a large Newfoundland kindred with a common MSH2 mutation

PURPOSE

This study was designed to provide precise estimates of death and cancer risks, by gender and parent of origin, in hereditary nonpolyposis colorectal cancer independent of mutation, geographic variation, and ascertainment bias.

METHODS

A group of 12 families with a founder MSH2 mutation (nucleotide 943+3, A --> T) causing hereditary nonpolyposis colorectal cancer was identified in Newfoundland. Genetic testing was offered to those at 50 percent risk of inheriting the mutation. Medical records were reviewed to identify cancer types, age at onset of cancer, and age at death. Ascertainment bias was limited by analyzing only sibships with good ascertainment of genetic status (> or =50 percent of sibships had known genetic status).

RESULTS

Of 302 family members with hereditary nonpolyposis colorectal cancer or at 50 percent risk, 151 (50 percent) were considered to be mutation carriers, 96 (32 percent) were mutation negative, and 55 (18 percent) were of unknown mutation status. By age 50 years, 72 percent of males and 72 percent of females who were hereditary nonpolyposis colorectal cancer mutation carriers had developed cancer. The age-related risks of colorectal cancer or of death of cancer were significantly higher in males than in females (relative risk = 2.8, P = 0.0001 and relative risk = 2.1, P = 0.01, respectively). The mutation was transmitted by the mother more frequently than the father. Females who inherited the mutation from their father had an increased risk of developing colorectal cancer (relative risk = 2.5, P = 0.05) and of dying of cancer (relative risk = 2.7, P = 0.04) compared with females who inherited the mutation from their mother.

CONCLUSIONS

Investigation of large kindreds from the same geographic area who share the same MSH2 mutation and in whom family members have been identified with little ascertainment bias suggests that the risks for colorectal cancer and death of cancer are higher for male mutation carriers than for females and that females who inherit the mutation from their father are at higher risk of colorectal cancer than females who inherit the mutation from their mother.

Familial risk of preeclampsia in Newfoundland: a population-based study

This study sought to quantify the familial risk of preeclampsia (proteinuric hypertension) in Newfoundland and to identify characteristics in probands that predict increased familial risk. Reviewed were 5173 obstetric charts from 10 hospitals, representing 99% of deliveries on the island of Newfoundland for a 1-yr period from April 1996 to March 1997; pregnancy-induced hypertension was diagnosed according to strict criteria. Family obstetric histories were obtained from identified probands with preeclampsia, and sisters and mothers of probands were interviewed. In addition, the obstetric charts from sisters and mothers were reviewed to identify preeclampsia. The incidence of preeclampsia in the population was 5.6% (n = 292), and in primiparous women it was 7.9%. Factors independently associated with increased risk of preeclampsia included primiparous delivery, multiple gestation, pregestational and gestational diabetes, maternal age of more than 35 yr, and region of the province. Of 330 sisters identified, 217 had 445 pregnancies, with 331 charts located for review. The incidence of preeclampsia (based on chart review) in 163 primiparous sisters was 20.2%. The relative risk of preeclampsia in primiparous sisters of probands with preeclampsia compared with primiparous women in the population was 2.6 (95% confidence interval, 1.8 to 3.6). Factors in probands independently associated with a higher risk of preeclampsia in sisters included at least 2+ proteinuria and region of the province. This population-based study, which used unbiased ascertainment and strict diagnostic criteria, demonstrated a significantly higher risk of preeclampsia in sisters of probands with preeclampsia, particularly when probands were defined by severity of preeclampsia and by geographic region.

Clinical and genetic epidemiology of inherited renal disease in Newfoundland

Clinical and genetic epidemiology of inherited renal disease in Newfoundland. Newfoundland's geography, settlement, and socioeconomic development have produced a population useful for the study of genetic diseases. This review examines the clinical and genetic epidemiologic studies of inherited renal diseases undertaken in this population in the past 15 years. Common founder effects and large families through each generation provided very extensive pedigrees with autosomal-dominant diseases, such as polycystic kidney disease (PKD) and von Hippel-Lindau disease. In the former disease the diagnostic utility of renal ultrasound was determined, as was the prognostic impact of genotype, the role of the renin-angiotensin system in the pre-hypertensive phase, the potential for somatic mutations of the PKD2 gene, or the combination of mutations in the PKD1 and PKD2 genes, in single cells to induce cysts, and the demonstration that human transheterozygotes of PKD1 and -2 are not embryonically lethal. The presence of multiple genetic isolates and the high coefficient of kinship have predisposed to autosomal recessive diseases such as Bardet-Biedl syndrome (BBS), autosomal-recessive PKD, primary hyperoxaluria, and dihydroxyadenine urolithiasis. We have reported the clinical manifestations and natural history of the BBS, with particular emphasis on the fact that renal abnormalities are cardinal manifestations of the disease, the presence of at least six different genotypes, the identity and function of the BBS6 gene, and the presence of three different BBS6 mutations. Because of its relatively homogenous origins and high coefficient of kinship, Newfoundland's population also may be useful for the study of complex diseases such as preeclampsia. Using unbiased ascertainment and strict diagnostic criteria, we have found a significant risk of preeclampsia and non-proteinuric gestational hypertension in sisters of probands with preeclampsia, particularly when probands are defined by severity of preeclampsia, an observation that supports a study to search for susceptibility genes. We conclude that collaborations between clinical epidemiologists and molecular geneticists, using the Newfoundland population, have provided important clinical and mechanistic insights into inherited renal diseases.