Genealogical Index Of Familiality Research Articles

Significant familial clustering of Peyronie's disease in close and distant relatives.

Peyronie's disease (PD) has previously been observed to co-aggregate in a small number of first-degree relative pairs (e.g., father-son). However, the familial aggregation of PD in more distant relatives, as well as the aggregation of Dupuytren's disease (DD) in probands and relatives, has not been thoroughly investigated. This study explored the evidence for familial clustering of PD and DD in close and distant relatives. The Utah Population Database, which includes genealogy information linked to electronic medical records (available since 1995), was used to identify men and their relatives with PD and DD based on ICD9/10 codes. All cases were required to have high-quality genealogy data. We estimated relative risk (RR) of PD and DD in first- through fifth-degree relatives compared to matched population rates of disease. We also investigated the average relatedness of cases compared to the average relatedness of sets of matched controls. Outcome measures include estimation of relative risk and excessive relatedness as measured by a Genealogical Index of Familiality (GIF) analysis. We analyzed 307 individuals with PD, and their first- through fifth-degree relatives. Approximately 0.12% of the population had PD, 95% of these were diagnosed over the age of 30 years (age range: 10-92 years), and 1.3% of PD probands had a comorbid diagnosis of DD. RR estimates for PD were significant for first- and fifth-degree relatives. RR estimates for DD were significant only for probands. The average relatedness of cases was significantly greater than matched controls, even after removing first- and second-degree relatives. We also found that 74.9% of identified PD probands belonged to pedigrees with a statistical excess of PD. Despite the low prevalence of PD in our healthcare records, the results provide evidence that support a genetic contribution to at least a subset of PD cases.

Evidence for excess familial clustering of Post Traumatic Stress Disorder in the US Veterans Genealogy resource

A genealogy of the United States has been record-linked to National Veteran's Health Administration (VHA) patient data to allow non-identifiable analysis of familial clustering. This genealogy, including over 70 million individuals linked to over 1 million VHA patients, is the largest such combined resource reported. Analysis of familial clustering among VHA patients diagnosed with Post Traumatic Stress Disorder (PTSD) allowed a test of the hypothesis of an inherited contribution to PTSD. PTSD is associated strongly with military service and extended familial clustering data have not previously been presented. PTSD-affected VHA patients with genealogy data were identified by presence of an ICD diagnosis code in the VHA medical record in at least 2 different years. The Genealogical Index of Familiality (GIF) method was used to compare the average relatedness of VHA patients diagnosed with PTSD with their expected average relatedness, estimated from randomly selected sets of matched linked VHA patient controls. Relative risks for PTSD were estimated in first-, second-, and third-degree relatives of PTSD patients who were also VHA patients, using sex and age-matched rates for PTSD estimated from all linked VHA patients. Significant excess pairwise relatedness, and significantly elevated risk for PTSD in first-, second-, and third-degree relatives was observed; multiple high-risk extended PTSD pedigrees were identified. The analysis provides evidence for excess familial clustering of PTSD and identified high-risk PTSD pedigrees. These results support an inherited contribution to PTSD predisposition and identify a powerful resource of high-risk PTSD pedigrees for predisposition gene identification.

Family aggregation analysis shows a possible heritable background of equine grass sickness (dysautonomia) in a Hungarian stud population.

Equine grass sickness (also known as dysautonomia) is a life-threatening polyneuropathic disease affecting horses with approx. 80% mortality. Since its first description over a century ago, several factors, such as the phenotype, intestinal microbiome, environment, management and climate, have been supposed to be associated with the increased risk of dysautonomia. In this retrospective study, we examined the possible involvement of genetic factors. Medical and pedigree datasets regarding 1,233 horses with 49 affected animals born during a 23-year period were used in the analysis. Among the descendants of some stallions, the proportion of animals diagnosed with dysautonomia was unexpectedly high. Among males, the odds of dysautonomia were found to be higher, albeit not significantly, than among females. Significant familial clustering (genealogical index of familiality, P = 0.001) was observed among the affected animals. Further subgroups were identified with significant (P < 0.001) aggregation among close relatives using kinship-based methods. Our analysis, along with the slightly higher disease frequency in males, suggests that dysautonomia may have a genetic causal factor with an X-linked recessive inheritance pattern. This is the first study providing ancestry data and suggesting a heritable component in the likely multifactorial aetiology of the disease.

Chronic Thromboembolic Pulmonary Hypertension Cases Cluster in Families

Chronic thromboembolic pulmonary hypertension (CTEPH) is a serious sequela of pulmonary embolism (PE) and occurs in about 3%of acute PE survivors. Common inherited thrombophilias, including the Factor V Leiden mutation, are not associated with increased risk of CTEPH, even though they increase the risk for VTE. Whether other inherited genetic factors contribute to the risk of developing CTEPH remains unknown. Familial clustering of a disease can indicate inherited genetic risk for that disease. In this study, the Utah Population Database (UPDB), a unique genealogy resource, was used to assess whether CTEPH cases cluster in families. Prevalent CTEPH patients in Utah were identified and were then matched to control subjects. Using the UPDB, the Genealogical Index of Familiality (a statistical measure of relatedness of individuals with a given phenotype) was calculated. The UPDB was also used to calculate the relative risk of CTEPH and VTE in the family members of patients with CTEPH. This study found that Utah patients with CTEPH are significantly more related than would be expected by chance, with both close and distant relationships identified. We also found that the relative risk of VTE was significantly increased among first-degree relatives of CTEPH probands. The study data suggest that heritable genetic factors influence an individual's risk of developing CTEPH, providing the strongest evidence to date for a genetic contribution to CTEPH risk. Although our data suggest that these inherited genetic factors likely also increase the risk for VTE, they are likely to be distinct from the common inherited thrombophilias.

A genealogical assessment of familial clustering of anorectal malformations.

Familial recurrence of anorectal malformations (ARMs) has been reported in single institution case series and in two population-based studies. Here, we investigate the familial aggregation of ARMs using well-established, unbiased methods in a population genealogy of Utah. Study subjects included 255 ARM cases identified from among the two largest healthcare providers in Utah with linked genealogy data using International Classification of Diseases, Ninth Revision (ICD-9) diagnosis codes. The genealogical index of familiality (GIF) statistic, which compares the average pair-wise relatedness of cases to sets of matched controls, was used to test excess familial clustering. We also estimated relative risks (RRs) for ARM and associated phenotypes in relatives of cases adjusting for age-, sex-, and birthplace. Significant excess familial clustering was observed for all ARM subjects (GIF p < 1e-3). Significant RR estimates for ARM (RR = 15.6, p = 3.3e-6), and for almost all co-morbid birth defects previously associated with ARM, were observed among first-degree relatives of ARM case subjects. This genealogically-based population survey of familial aggregation of ARMs confirms the presence of a heritable component to ARMs and provides unbiased risk estimates to relatives of cases, which may have clinical utility.

Evidence of an Inherited Predisposition for Spinal Cord Tumors

Study Design:Retrospective study.Objectives:To determine familial clustering of primary spinal cord tumors using a statewide genealogy database.Methods:The Utah Population Database (UPDB) was queried using ICD-Oncology (International Classification of Diseases for Oncology) codes for primary spinal cord tumors. The hypothesis of disproportionate familial clustering was tested using the Genealogical Index of Familiality (GIF). The relative risks (RRs) in relatives were calculated using the ratio of observed spinal cord tumors to expected spinal cord tumors in relatives using estimated rates from the UPDB. The related clusters of spinal cord cancer cases with a significant excess number of spinal cord cancer cases descending from a common founder pair were identified using internal UPDB rates.Results:The analysis of the GIF for individual with tumors of the spinal cord showed excess close and distant relatedness (case GIF = 3.82; control mean GIF = 2.68; P = .068). Excess relatedness for spinal cord cancers was observed when only more distant relationships were considered (P = .019). The RRs for spinal cord tumors were elevated in second- and third-degree relatives but this did not reach statistical significance (RR = 2.9, P = .15, and RR = 2.0, P = .14). Multiple extended pedigrees with a significant excess of spinal cord cancer cases among the descendants were identified.Conclusions:The excess relatedness of tumor cases over controls in distant relationships, the higher RRs to distant relatives, and the discovery of high-risk pedigrees all suggest a familial predisposition to the development of spinal cord tumors.

A description of familial clustering of meningiomas in the Utah population.

Meningiomas are common intracranial tumors in adults, yet the genetics and cause of sporadic meningiomas are not well understood. Few familial clusters have been reported. The aim of this study was to investigate the familiality of meningiomas within the Utah Population Database. Meningioma cases reported in the Utah Cancer Registry were identified. Relative risk of their relatives was calculated. All possible cases were assessed with the Genealogical Index of Familiality (GIF), which measures average pairwise relatedness of all possible pairs using the Malecot coefficient of kinship. Clusters of cases descending from a common ancestor were identified. Eight hundred fifty-eight meningioma cases were reported. The relative risk of a first- or second-degree relative was 3.13 (95% CI: 1.67, 5.36) or 2.28 (1.30, 3.70), respectively. The GIF statistic demonstrated a clear excess of relationships for genetic distance <4 (closer than first cousins). We identified 920 pedigrees, including 2-21 meningioma cases. One hundred eighty-nine of these pedigrees, including 2-15 cases, had a significant excess (P < 0.05) of meningioma cases over what was expected. This Utah population-based analysis of meningiomas shows clear evidence of familial clustering and supports both a familial and a germline variant basis for meningioma. These clusters may allow identification of genes likely to contribute to tumorigenesis in high-risk pedigrees. These relative risk data provide the basis for further investigations of genetic contributions to meningioma. These data may contribute to developing a basis for determining screening criteria of higher-risk pedigrees for the presence of meningiomas.

Population-based description of familial clustering of Chiari malformation Type I.

OBJECTIVE A population-based genealogical resource with linked medical data was used to define the observed familial clustering of Chiari malformation Type I (CM-I). METHODS All patients with CM-I were identified from the 2 largest health care providers in Utah; those patients with linked genealogical data were used to test hypotheses regarding familial clustering. Relative risks (RRs) in first-, second-, and third-degree relatives were estimated using internal cohort-specific CM-I rates; the Genealogical Index of Familiality (GIF) test was used to test for an excess of relationships between all patients with CM-I compared with the expected distribution of relationships for matched control sets randomly selected from the resource. Pedigrees with significantly more patients with CM-I than expected (p < 0.05) based on internal rates were identified. RESULTS A total of 2871 patients with CM-I with at least 3 generations of genealogical data were identified. Significantly increased RRs were observed for first- and third-degree relatives (RR 4.54, p < 0.001, and RR 1.36, p < 0.001, respectively); the RR for second-degree relatives was elevated, but not significantly (RR 1.20, p = 0.13). Significant excess pairwise relatedness was observed among the patients with CM-I (p < 0.001), and borderline significant excess pairwise relatedness was observed when all relationships closer than first cousins were ignored (p = 0.051). Multiple extended high-risk CM-I pedigrees with closely and distantly related members were identified. CONCLUSIONS This population-based description of the familial clustering of 2871 patients with CM-I provided strong evidence for a genetic contribution to a predisposition to CM-I.

Evaluation of a New Genetic Epidemiology Resource: The Intermountain Genealogy Registry

Background: Many landmark genetic breakthroughs, including the recent discovery of PCSK-9 inhibitor drugs, were accomplished with substantial contributions from evaluation of pedigrees. Finding and ascertaining high-value pedigrees is not trivial and requires considerable time and cost. Here, we describe the creation of the Intermountain Genealogy Registry for use in studying the genetics of cardiovascular and other diseases. Methods: Using publicly available pedigree records and probabilistic linkage techniques, we created a genealogy of ≈23 million records that we linked to 3.9 million patient records in the Intermountain Healthcare system. Analytical tools were developed to support this registry, including calculation of genealogical index of familiality (GIF), testing of familial coaggregation of diseases, and extraction of high-risk pedigrees. Results: A total of 658,822 (16.8%) patients were linked to a genealogy pedigree record. The average age of the linked patients was 53 years, the majority (89.0%) were Caucasian, and 50.5% were male. The GIFs for the leading cardiovascular conditions of atrial fibrillation, coronary artery disease, heart failure, and myocardial infarction (MI) were all 1.2 times greater than the GIFs of matched control sets (p < 0.001). For extreme values of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides, the GIFs were each 1.5 times greater than those of matched control sets (p < 0.001). There was coaggregation with MI and the extreme lipid traits with the largest coaggregation being for MI and triglycerides. Conclusion: The Intermountain Genealogy Registry is a multifaceted resource created to provide insights into the genetic components of cardiovascular and other diseases. This registry provides the means for easy identification and ascertainment of high-risk pedigrees for discovery of genetic susceptibility variants.

Genetic Analysis of Low BMI Phenotype in the Utah Population Database

The low body mass index (BMI) phenotype of less than 18.5 has been linked to medical and psychological morbidity as well as increased mortality risk. Although genetic factors have been shown to influence BMI across the entire BMI, the contribution of genetic factors to the low BMI phenotype is unclear. We hypothesized genetic factors would contribute to risk of a low BMI phenotype. To test this hypothesis, we conducted a genealogy data analysis using height and weight measurements from driver's license data from the Utah Population Data Base. The Genealogical Index of Familiality (GIF) test and relative risk in relatives were used to examine evidence for excess relatedness among individuals with the low BMI phenotype. The overall GIF test for excess relatedness in the low BMI phenotype showed a significant excess over expected (GIF 4.47 for all cases versus 4.10 for controls, overall empirical p-value<0.001). The significant excess relatedness was still observed when close relationships were ignored, supporting a specific genetic contribution rather than only a family environmental effect. This study supports a specific genetic contribution in the risk for the low BMI phenotype. Better understanding of the genetic contribution to low BMI holds promise for weight regulation and potentially for novel strategies in the treatment of leanness and obesity.

Strong Evidence for a Genetic Contribution to Late-Onset Alzheimer’s Disease Mortality: A Population-Based Study

BackgroundAlzheimer’s disease (AD) is an international health concern that has a devastating effect on patients and families. While several genetic risk factors for AD have been identified much of the genetic variance in AD remains unexplained. There are limited published assessments of the familiality of Alzheimer’s disease. Here we present the largest genealogy-based analysis of AD to date.MethodsWe assessed the familiality of AD in The Utah Population Database (UPDB), a population-based resource linking electronic health data repositories for the state with the computerized genealogy of the Utah settlers and their descendants. We searched UPDB for significant familial clustering of AD to evaluate the genetic contribution to disease. We compared the Genealogical Index of Familiality (GIF) between AD individuals and randomly selected controls and estimated the Relative Risk (RR) for a range of family relationships. Finally, we identified pedigrees with a significant excess of AD deaths.ResultsThe GIF analysis showed that pairs of individuals dying from AD were significantly more related than expected. This excess of relatedness was observed for both close and distant relationships. RRs for death from AD among relatives of individuals dying from AD were significantly increased for both close and more distant relatives. Multiple pedigrees had a significant excess of AD deaths.ConclusionsThese data strongly support a genetic contribution to the observed clustering of individuals dying from AD. This report is the first large population-based assessment of the familiality of AD mortality and provides the only reported estimates of relative risk of AD mortality in extended relatives to date. The high-risk pedigrees identified show a true excess of AD mortality (not just multiple cases) and are greater in depth and width than published AD pedigrees. The presence of these high-risk pedigrees strongly supports the possibility of rare predisposition variants not yet identified.

A population-based analysis of clustering identifies a strong genetic contribution to lethal prostate cancer

Background: Prostate cancer is a common and often deadly cancer. Decades of study have yet to identify genes that explain much familial prostate cancer. Traditional linkage analysis of pedigrees has yielded results that are rarely validated. We hypothesize that there are rare segregating variants responsible for high-risk prostate cancer pedigrees, but recognize that within-pedigree heterogeneity is responsible for significant noise that overwhelms signal. Here we introduce a method to identify homogeneous subsets of prostate cancer, based on cancer characteristics, which show the best evidence for an inherited contribution.Methods: We have modified an existing method, the Genealogical Index of Familiality (GIF) used to show evidence for significant familial clustering. The modification allows a test for excess familial clustering of a subset of prostate cancer cases when compared to all prostate cancer cases.Results: Consideration of the familial clustering of eight clinical subsets of prostate cancer cases compared to the expected familial clustering of all prostate cancer cases identified three subsets of prostate cancer cases with evidence for familial clustering significantly in excess of expected. These subsets include prostate cancer cases diagnosed before age 50 years, prostate cancer cases with body mass index (BMI) greater than or equal to 30, and prostate cancer cases for whom prostate cancer contributed to death.Conclusions: This analysis identified several subsets of prostate cancer cases that cluster significantly more than expected when compared to all prostate cancer familial clustering. A focus on high-risk prostate cancer cases or pedigrees with these characteristics will reduce noise and could allow identification of the rare predisposition genes or variants responsible.

Evidence of an Inherited Predisposition for Cervical Spondylotic Myelopathy

A retrospective, population-based study cross-referencing a genealogic database of over 2 million Utah residents with 10 years of clinical diagnosis data from a large tertiary hospital. The objective of this study is to determine the presence or absence of an inherited predisposition to the development of cervical spondylotic myelopathy (CSM). A genetic predisposition for the development of cervical spondylosis has been discussed in the literature with low-quality evidence. Families with a high incidence of disease or early-onset disease in monozygotic twins have both been reported. However, these suggestions of an inherited predisposition for disease have never been rigorously studied. The purpose of this study is to determine a genetic predisposition among patients diagnosed with CSM. The Utah Population Database combines health and genealogic data on over 2 million Utah residents. International Classification of Diseases, Ninth Revision (ICD-9) codes were used to identify 486 patients in the database with a diagnosis of CSM (ICD-9 code 721.1). The hypothesis of excessive familial clustering was tested using the Genealogical Index of Familiality (GIF), and relative risks (RRs) in relatives were estimated by comparing rates of disease in relatives with rates estimated in the relatives of five matched controls for each case. This methodology has been previously reported and validated for other disease conditions but not for CSM. The GIF analysis for patients with CSM showed significant excess relatedness for disease (P < 0.001). RRs were significantly elevated in both first- (RR = 5.21, CI = 2.1-13.2, P < 0.001) and third-degree relatives (RR = 1.95, CI = 1.04-3.7, P < 0.05). Excess relatedness of cases and significantly elevated RRs to both close and distant relatives supports an inherited predisposition to CSM.

A population-based assessment of the familial component of acute kidney allograft rejection

The genetic determinants of acute kidney transplant rejection (AR) are not well studied, and familial aggregation has never been demonstrated. The goal of this retrospective case-control study was to exploit the unique nature of the Utah Population Database (UPDB) to evaluate if AR or rejection-free survival aggregates in families. We identified 891 recipients with genealogy data in the UPDB with at least one year of follow-up, of which 145 (16.1%) had AR and 77 recipients had biopsy-proven rejection graded >or=1A. We compared the genealogical index of familiality (GIF) in cases and controls (i.e. recipients with random assignment of rejection status). We did not find evidence for familial clustering of AR in the entire patient population or in the subgroup with early rejection (n = 52). When the subgroup of recipients with rejection grade >or=1A (n = 77) was analysed separately, we observed increased familial clustering (GIF = 3.02) compared to controls (GIF = 1.96), although the p-value did not reach the level of statistical significance (p = 0.17). Furthermore, we observed an increase in familial clustering in recipients who had a rejection-free course (GIF = 2.45) as compared to controls (GIF = 2.08, p = 0.04). When all recipients were compared to non-transplant controls, they demonstrated a much greater degree of familiality (GIF = 2.03 versus GIF 0.63, p < 0.001). There is a familial component to rejection-free transplant course and trend to familial aggregation in recipients with AR grade 1A or higher. If a genetic association study is performed, there are families in Utah identified in the current study that can be targeted to increase the power of the test.

Familiality of Diabetes Mellitus

The aims of this study were to estimate relative risk for type 1 and type 2 diabetes in relatives of diabetic patients, and to test for excess relatedness among diabetic patients. Additionally, the difference in parental transmission of diabetes was investigated. This study used a unique Utah genealogical resource, linked to electronic medical records of the largest health provider in Utah. We identified 19,640 patients with a diagnosis of type 1 or type 2 diabetes. Relative Risks (RRs) for type 1 and type 2 diabetes were assessed for first-, second- and third-degree relatives of diabetic patients. The observed average relatedness of diabetic patients was compared to the expected relatedness using the Genealogical Index of Familiality (GIF). We observed significantly elevated RRs for type 1 diabetes in first-degree (RR=8.68; P<0.0001), second-degree (RR=1.93; P<0.0001) and third-degree relatives (RR=1.74; P<0.0001) of type 1 diabetic patients. RRs for type 2 diabetes were significantly increased in first-degree (RR=2.24; P<0.0001), second-degree (RR=1.36; P<0.0001) and third-degree relatives (RR=1.14; P<0.0001) of type 2 diabetic patients. Significantly increased RRs for type 1 diabetes were observed in the relatives of type 2 diabetic patients, and vice versa. The GIF analysis showed significant excess relatedness for type 1 diabetes cases, and independently for type 2 diabetes cases. Offspring of diabetic fathers were at significantly higher risk for type 1 diabetes than offspring of diabetic mothers (RR=9.73; P<0.0001 compared to RR=4.99; P<0.0001). No significant difference in parental transmission was observed for type 2 diabetes. Our results strongly support the existence of a genetic contribution to both type 1 and type 2 diabetes, and additionally suggest a relationship between both types of diabetes. Furthermore, our results suggest a significant difference in parental transmission of type 1 diabetes.

Identification of excess clustering of coronary heart diseases among extended pedigrees in a genealogical population database

First-degree family history of early coronary artery disease (CAD) and myocardial infarction (MI) is prognostic among disease-free individuals but may be unreliable. This study evaluated deaths caused by CAD, MI, hypertensive heart disease (HtnHD), and congestive heart failure (CHF) among close and distant relatives. The Utah Population Database contains >2.2 million individual records with genealogy data and 250,000 linked death certificates. Deaths caused by CAD (n = 28,469), MI (n = 26,468), HtnHD (n = 3933), and CHF (n = 11,784) were studied. Familial relative risks (FRRs) were assessed for first- and second-degree relatives. Familiality was also evaluated using the Genealogical Index of Familiality (GIF), which considers close and distant genetic relationships in the Utah Population Database. Familial relative risks in first-degree (FRR = 1.25, P < .0001) and second-degree (FRR = 1.06, P = .0002) relatives were significant for early age at MI death (<65 years old). Genealogical Index of Familiality analysis demonstrated excess relatedness for deaths caused by MI (case GIF 2.93, mean control GIF 2.73, P < .001) and CHF (2.92 vs 2.66, P < .001). For early age at death, GIFs were significant for MI (3.06 vs 2.54, P < .001), HtnHD (3.22 vs 2.44, P = .003), and CHF (2.64 vs 2.23, P = .003). Deaths caused by MI and CHF demonstrate a heritable component in close and distant relatives. For MI, CHF, and HtnHD, for which findings were more pronounced in early age at death, gene discovery may be most effective among early-onset clusters. Excess relatedness was not found for CAD death--perhaps because of heterogeneity within the phenotype--suggesting that this may be a suboptimal phenotype for genetic study.

Familial aggregation of atrial fibrillation in Iceland

To examine the heritability of atrial fibrillation (AF) in Icelanders, utilizing a nationwide genealogy database and population-based data on AF. AF is a disorder with a high prevalence, which has been known to cluster in families, but the heritability of the common form has not been well defined. The study population included 5269 patients diagnosed since 1987 and age-sex-matched controls randomly selected from the genealogy database. Kinship coefficients (KC), expressed as genealogical index of familiality (GIF = average KC x 100,000), were calculated before and after exclusion of relatives separated by one to five meiotic events. Risk ratios (RR) were calculated for first- to fifth-degree relatives. The average pairwise GIF among patients with AF was 15.9 (mean GIF for controls 13.9, 95%CI = 13.3, 14.4); this declined to 15.4 (mean GIF for controls 13.6, 95%CI = 13.1, 14.2) after exclusion of relatives separated by one meiosis and to 13.7 (mean GIF for controls 12.6, 95%CI = 12.1, 13.2), 12.7 (mean GIF for controls 11.9, 95%CI = 11.4, 12.4), and 11.3 (mean GIF for controls 10.6, 95%CI = 10.1, 11.1) after exclusion of relatives within two, three, and four meioses, respectively (all P<0.00001). RRs among relative pairs also declined incrementally, from 1.77 in first-degree relatives to 1.36, 1.18, 1.10, and 1.05 in second- through fifth-degree relatives (all P<0.001), consistent with the declining proportion of alleles shared identically by descent. When the analysis was limited to subjects diagnosed with AF before the age of 60, first-degree relatives of the AF cases were nearly five times more likely to have AF than the general population. AF shows strong evidence of heritability among unselected patients in Iceland, suggesting that there may be undiscovered genetic variants underlying the risk of the common form of AF.

Lobular breast cancer: Excess familiality observed in the Utah Population Database

Family history of breast cancer (BC) is a strong predictor for developing female BC. Whether this excess familiality differs within morphological BC subgroups remains unclear. We assessed the risk of lobular breast cancer (LOB) and any BC among relatives of probands with LOB. We used the Utah Population Database (UPDB) to estimate familial relative risks (FRR) as well as average relatedness, using the genealogical index of familiality (GIF) statistic. The UPDB, a population-based resource, links genealogical data from over 2 million individuals to the Utah Cancer Registry. Consistent with other studies, analysis of all BC cases showed significantly increased risk of BC to relatives (first-degree relative [FDR]: FRR = 1.83, 95% confidence interval [CI] = 1.75-1.90). Morphology-specific risks showed that relatives of LOB probands had an increased risk of LOB (FDR: FRR = 4.51, 95% CI = 2.79-6.89) and an increased risk of any BC (FDR: FRR = 2.47, 95% CI = 2.12-2.85); both measures were significantly greater than the all BC FRR estimates, and surpassed even generalized early-onset BC risk. GIF analyses corroborated the FRR results and indicated that the excess relatedness of LOB cases extended to third-degree relatives. Our findings suggest that LOB has a heritable component and may represent a genetically homogeneous form of BC. Pedigrees with excess LOB may be useful in isolating additional BC predisposition genes. Relatives of women with LOB are at higher risk for BC than relatives of other BC subtypes; a more rigorous BC screening regime may be warranted for these individuals.