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Archives of Oral Biology Aug 2023To determine the association between genetic factors and molar-incisor hypomineralisation (MIH) and/or hypomineralised second primary molars by means of a systematic... (Review)
Review
OBJECTIVE
To determine the association between genetic factors and molar-incisor hypomineralisation (MIH) and/or hypomineralised second primary molars by means of a systematic review.
DESIGN
A search was performed in Medline-PubMed, Scopus, Embase and Web of Science databases; manual search and search in gray literature were also performed. Selection of articles was performed independently by two researchers. A third examiner was involved in cases of disagreement. Data extraction was performed using an Excel® spreadsheet and independent analysis was performed for each outcome.
RESULTS
Sixteen studies were included. There was an association between MIH and genetic variants related to amelogenesis, immune response, xenobiotic detoxification and other genes. Moreover, interactions between amelogenesis and immune response genes, and SNPs in the aquaporin gene and vitamin D receptors were associated with MIH. Greater agreement of MIH was found in pairs of monozygotic twins than dizygotic twins. The heritability of MIH was 20 %. Hypomineralised second primary molars was associated with SNPs in the hypoxia-related HIF-1 gene and methylation in genes related to amelogenesis.
CONCLUSION
With very low or low certainty of evidence, an association was observed between MIH and SNPs in genes associated with amelogenesis, immune response, xenobiotic detox and ion transport. Interactions between genes related to amelogenesis and immune response as well as aquaporin genes were associated to MIH. With very low certainty of evidence, hypomineralised second primary molars was associated to a hypoxia-related gene and to methylation in genes related to amelogenesis. Moreover, higher agreement of MIH in pairs of monozygotic twins than dizygotic twins was observed.
Topics: Humans; Dental Enamel Hypoplasia; Molar Hypomineralization; Xenobiotics; Amelogenesis; Molar; Prevalence
PubMed: 37210809
DOI: 10.1016/j.archoralbio.2023.105716 -
Stroke Jan 2004To design appropriate molecular genetic studies, we first need to understand the genetic epidemiology of stroke. We therefore performed a systematic review of the... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND AND PURPOSE
To design appropriate molecular genetic studies, we first need to understand the genetic epidemiology of stroke. We therefore performed a systematic review of the literature to assess the heritability of stroke according to methodological quality of studies and to determine any heterogeneity in findings between studies and possible publication bias.
METHODS
We searched for twin studies and studies of family history of stroke using bibliographic databases and by hand-searching reference lists and journals. Odds ratios (ORs) for family history as a risk factor for stroke were calculated within studies and combined by meta-analysis. Heterogeneity between studies, methodological quality of studies, and the influence of the age at which stroke occurred in both probands and relatives were assessed.
RESULTS
We identified 53 independent studies (3 twin, 33 case-control, and 17 cohort). Monozygotic twins were more likely to be concordant than dizygotic twins (OR, 1.65; 95% CI, 1.2 to 2.3; P=0.003). A positive family history was a risk factor for stroke in both case-control (OR, 1.76; 95% CI, 1.7 to 1.9; P<0.00001) and cohort (OR, 1.30; 95% CI, 1.2 to 1.5; P<0.00001) studies. However, there was major heterogeneity between studies (cohort P=0.0001; case-control P<0.00001), with much stronger associations in small studies and methodologically less rigorous studies. Moreover, studies that reported insufficient data to allow meta-analysis tended to have found weaker associations. Family history of stroke was more frequent in studies that were confined to probands or relatives aged <70 years. However, few studies considered the number of affected and unaffected relatives, only 2 studies considered stroke phenotypes in detail, and only 19 studies (38%) adjusted associations for intermediate phenotypes. No twin study, only 5 cohort studies (26%), and 20 case-control studies (61%) differentiated between ischemic and hemorrhagic stroke in the proband. Family history of stroke was more frequent in large- and small-vessel stroke than in cardioembolic stroke. There were very few data on the influence of family history on stroke severity and no data on stroke recovery.
CONCLUSIONS
Twin studies suggest a small genetic contribution to stroke, but reliable interpretation of published family history studies is undermined by major heterogeneity, insufficient detail, and potential publication and reporting bias. More detailed large-scale genetic epidemiology is required.
Topics: Bias; Brain Ischemia; Case-Control Studies; Cohort Studies; Epidemiologic Methods; Epidemiologic Research Design; Genetic Predisposition to Disease; Humans; Publication Bias; Risk Factors; Stroke; Twin Studies as Topic
PubMed: 14684773
DOI: 10.1161/01.STR.0000107187.84390.AA -
Journal of Neurosurgery. Spine Apr 2024Chiari malformations (CMs) are a group of congenital or acquired disorders characterized by hindbrain overcrowding into an underdeveloped posterior cranial fossa. CM is... (Review)
Review
OBJECTIVE
Chiari malformations (CMs) are a group of congenital or acquired disorders characterized by hindbrain overcrowding into an underdeveloped posterior cranial fossa. CM is considered largely sporadic-however, there exists growing evidence of transmissible genetic underpinnings. The purpose of this systematic review of all familial studies of CM was to investigate the existence of an inherited component and provide recommendations to manage and monitor at-risk family members.
METHODS
This paper includes the following: 1) a unique case report of dizygotic twins who presented at the Toronto Western Hospital Spinal Cord Clinic with symptomatic CM type 1 (CM-1) and syringomyelia; and 2) a systematic review of familial CM. The EMBASE and MEDLINE databases were searched on June 27, 2023, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only articles in the English language concerning the diagnosis of CM in > 1 human family member presented as a case study, case series, or literature review were included.
RESULTS
Among the 29 articles included in the final analysis, a total of 34 families with CM were analyzed. An average of 3 cases of CM were found per family among all generations. Eighty-one cases (88%) reported CM-1, whereas the other 11 (12%) cases reported either CM-0, CM-1.5, or tonsillar ectopia. A syrinx was present in 37 (54%) cases, with 14 (38%) of these patients also reporting a skeletal abnormality, the most common comorbidity. Most family members diagnosed with CM were siblings (18; 35%), followed by monozygotic twins/triplets (12; 23%).
CONCLUSIONS
Patients most often presented with headaches, sensory disturbances, or generalized symptoms. Overall, there exists mounting evidence for a hereditary component of CM. It is unlikely to be explained by a classic mendelian inheritance pattern, but is rather a polygenic architecture influenced by variable penetrance, cosegregation, and entirely nongenetic factors. For first-degree relatives of those affected by CM, the authors' findings may influence clinicians to conduct closer clinical and radiographic monitoring, promote patient education, and consider earlier genetic testing.
PubMed: 38608294
DOI: 10.3171/2024.1.SPINE231277 -
Pediatric Surgery International Aug 2020Biliary atresia (BA) in twins is extremely rare reported in the literature, but twin studies are useful methods of examining the associated factors of a complex disease.... (Meta-Analysis)
Meta-Analysis
PURPOSE
Biliary atresia (BA) in twins is extremely rare reported in the literature, but twin studies are useful methods of examining the associated factors of a complex disease. The objective of this study was to analyze the characteristics and patterns of biliary atresia in twins from reviewing available articles.
METHODS
PubMed and EMBASE databases were reviewed for related articles using the keywords ''biliary atresia'', ''twins'', ''monozygotic (MZ)'', and ''dizygotic (DZ)'', including relevant papers in the reference lists.
RESULTS
This analysis was extracted from 12 articles, with a total of 35 twin pairs included. BA was found in 36 out of 70 twin subjects (51.4%), of which had an even gender split. 97.1% twins were discordant, among 55.9% of which were monozygotic twin sets, indicating that BA may be related to genetic phenotype or penetrance. Isolated BA was the largest group with 27 (75%) affected twins. Only one pair of dizygotic twins (2.9%) demonstrate concordance for BA, and have one affected family member.
CONCLUSION
BA was found in nearly half of twin subjects with an even gender split. Isolated BA was the largest group, in which the number of monozygotic twins was similar with dizygotic twins, so the onset of the disease may not associate with the zygosity of twins. Most of twin sets had discordant disease presentation, especially monozygotic twins therein, emphasizing the role of epigenetic factor in the pathogenesis of BA. Future studies should take genetic testing among any twin sets in BA, especially the disease-associated mutations, thus be useful to investigate the etiology of disease.
Topics: Adult; Biliary Atresia; Diseases in Twins; Female; Humans; Male; Twins
PubMed: 32504124
DOI: 10.1007/s00383-020-04690-4 -
Otology & Neurotology : Official... Feb 2023Congenital cytomegalovirus infection is the leading nonhereditary cause of pediatric sensorineural hearing loss. This systematic review evaluated infection concordance...
OBJECTIVE
Congenital cytomegalovirus infection is the leading nonhereditary cause of pediatric sensorineural hearing loss. This systematic review evaluated infection concordance and comparative hearing abilities in twins/multiple births to model infection patterns.
DATABASES REVIEWED
PubMed, Embase, Web of Science, and Google Scholar.
METHODS
Studies that reported hearing outcomes of congenital cytomegalovirus infection in at least one multiple birth were eligible. Concordant infections (both twins) and discordant infections (single twin) were included. Multiple reviewers performed data extraction and quality assessment. Analyses involved relative risk of infection concordance by zygosity and chorionicity and odds of hearing loss by infection concordance. Hearing outcomes were compared between siblings.
RESULTS
Of 247 studies screened, 31 were included (74.2% high quality). The review captured 40 eligible multiple births. Among infected patients, 42.9% (95% confidence interval, 31.2-55.2%) demonstrated hearing loss. All uninfected twins had normal hearing. Most infections were concordant, and infected patients experienced 4.11 (1.18-14.36) times greater odds of hearing loss if their twin was also infected ( p = .02). Yet siblings' hearing outcomes diverged in over 40% of concordant cases. If either twin is infected, infection risk in the second twin is 3.25 (1.83-5.79) times greater in monozygotic than dizygotic twins and 2.50 (1.61-3.88) times greater in monochorionic than dichorionic twins (both p < .001). We describe a case from our practice.
CONCLUSION
Congenital cytomegalovirus infection patterns and hearing outcomes can vary widely even within a shared fetal and postnatal environment. Suspected infection in a twin indicates that both should receive testing and continued monitoring for late-onset sequelae.
Topics: Pregnancy; Female; Humans; Child; Pregnancy, Multiple; Twins, Dizygotic; Cytomegalovirus Infections; Hearing
PubMed: 36538753
DOI: 10.1097/MAO.0000000000003776 -
Genetic and epigenetic influences of twins on the pathogenesis of craniosynostosis: a meta-analysis.Plastic and Reconstructive Surgery Apr 2012The pathoetiology of craniosynostosis is not well understood. It likely results from a combination of genetic and epigenetic phenomena, such as intrauterine constraint... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The pathoetiology of craniosynostosis is not well understood. It likely results from a combination of genetic and epigenetic phenomena, such as intrauterine constraint from multiple gestations. Information on craniosynostosis in twins is limited to case reports and series. The authors conducted a systematic review and meta-analysis of the literature to elucidate the genetic and nongenetic influences of twins on the pathogenesis of craniosynostosis.
METHODS
PubMed and Ovid databases were reviewed for the key terms "craniosynostosis and twins." Data analyzed included demographical information, incidence rates, concordance, and phenotypic variability. Risk factors for craniosynostosis, concordance, and phenotypic variability were assessed by univariate and multivariate analyses. A case series was presented.
RESULTS
Data were extracted from 34 journal articles, including the authors' five patients, and representing a total of 199 twins with craniosynostosis. Twinning was 2.62 times greater in patients with craniosynostosis (6.29 percent) compared with unaffected controls (2.4 percent; p < 0.0001). Boys were affected more than girls (65.30 versus 34.70 percent, respectively; p < 0.0001). Monozygotic concordance rates were greater than dizygotic (60.90 versus 5.30 percent, respectively; p < 0.0001) but were not 100 percent. Phenotypic variability was present in 62 percent of monozygotic twin sets (p < 0.05).
CONCLUSIONS
Increased concordance rates among monozygotic compared with dizygotic twins confirm the genetic role of twins on craniosynostosis. Evidence to support the epigenetic influence of twinning on the pathogenesis of craniosynostosis includes the elevated incidence of twins among a craniosynostotic population compared with unaffected twins in the general population and male gender predominance, as well as monozygotic phenotypic variability and discordance.
CLINICAL QUESTION/LEVEL OF EVIDENCE
Risk, IV.
Topics: Craniosynostoses; Diseases in Twins; Epigenesis, Genetic; Female; Humans; Infant; Male; Twins, Dizygotic; Twins, Monozygotic
PubMed: 22456364
DOI: 10.1097/PRS.0b013e31824422a8 -
Twin Research and Human Genetics : the... Apr 2017Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably... (Review)
Review
Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably more common than previously has been recognized. In this article, we will review all available cases of monochorionic dizygotic (MCDZ) twins. A total of 31 twins have been described in literature. A monochorionic diamniotic placenta is reported in all cases. Assisted reproductive technology is responsible for the origin of the pregnancy in 82.1% of the cases. In 15.4% of the sex-discordant twins, a genital anomaly was reported in one of the twins. Chimerism is demonstrable in 90.3% of the twins, leading to various diagnostic difficulties. As this review shows that most MCDZ twins are discovered by accident, it can be argued that it is far more common than has been assumed until now. However, the prevalence is still unclear. Awareness of MCDZ twinning is important, with subsequently correct medical strategies. Similarly, the resulting (blood) chimerism is essential to consider in diagnostic procedures, pre- and postnatally. More research on the effect of placental transfusion between sex-discordant twins is required.
Topics: Chimerism; Chorion; Female; Humans; Male; Placenta; Pregnancy; Pregnancy, Twin; Reproductive Techniques, Assisted; Twins, Dizygotic; Ultrasonography, Prenatal
PubMed: 28236812
DOI: 10.1017/thg.2017.4 -
Journal of Ultrasound in Medicine :... Nov 2007Congenital heart defects (CHDs) affect approximately 0.5% of all neonates. Recent literature points to a possible increase in the CHD prevalence among... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
Congenital heart defects (CHDs) affect approximately 0.5% of all neonates. Recent literature points to a possible increase in the CHD prevalence among monochorionic/diamniotic (MC/DA) twin gestations. We hypothesized that MC/DA twin pregnancy is a risk factor for CHD.
METHODS
A systematic review of all published English literature was conducted on MEDLINE (Ovid and PubMed) from January 2000 through April 2007 using the medical subject heading terms "congenital heart defect" and "monozygotic twins." Four observational studies were included in the final analysis. Published historical data were used for the population background risk of CHD. Relative risk (RR) estimates with 95% confidence intervals (CIs) were calculated by fixed and random effect models.
RESULTS
We included a total of 40 fetuses with CHDs among 830 fetuses from MC/DA twin gestations. Compared with the population, CHDs were significantly more prevalent in MC/DA twins regardless of the presence of twin-twin transfusion syndrome (TTTS) (RR, 9.18; 95% CI, 5.51-15.29; P < .001). Monochorionic/diamniotic twin gestations affected by TTTS were more likely to be complicated by CHDs than those that did not have TTTS (RR, 2.78; 95% CI, 1.03-7.52; P = .04). Ventricular septal defects were the most frequent heart defects. Pulmonary stenosis and atrial septal defects were significantly more prevalent in pregnancies complicated with TTTS.
CONCLUSIONS
Monochorionic/diamniotic twin gestation appears to be a risk factor for CHDs. Conditions that lead to abnormal placentation may also contribute to abnormal heart development, especially in MC/DA twin pregnancies complicated with TTTS. Fetal echocardiography may be considered for all MC/DA twin gestations because ventricular septal defects and pulmonary stenosis are the most common defects.
Topics: Diseases in Twins; Female; Heart Defects, Congenital; Humans; Internationality; Pregnancy; Prevalence; Risk Assessment; Risk Factors; Twins, Dizygotic; Twins, Monozygotic
PubMed: 17957043
DOI: 10.7863/jum.2007.26.11.1491 -
International Journal of Epidemiology Oct 2004An inverse association between birthweight and later blood pressure has been found in many studies in singletons. Twin studies have been used to examine whether genetic... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
An inverse association between birthweight and later blood pressure has been found in many studies in singletons. Twin studies have been used to examine whether genetic factors or family environment could account for this association.
METHODS
A systematic review identified 10 studies covering 3901 twin pairs. Meta-analysis of regression coefficients for the association between birthweight and systolic blood pressure was carried out for unpaired versus paired associations and for paired associations in dizygotic versus monozygotic pairs.
RESULTS
After adjustment for current weight or body mass index (BMI), the difference in systolic blood pressure per kg birthweight was -2.0 (95% CI: -3.2, -0.8) mmHg in the unpaired analysis and -0.4 (95% CI: -1.5, 0.7) mmHg in the paired analysis in the same subjects. In the paired analysis by zygosity, in all twins the coefficients were -0.7 (95% CI: -2.3, 0.8) mmHg in dizygotic pairs and -0.8 (95% CI: -2.1, 0.4) mmHg in monozygotic pairs, but in studies which included zygosity tests the coefficients were -1.0 (95% CI: -3.3, 1.6) mmHg in dizygotic pairs and -0.4 (95% CI: -1.9, 1.3) mmHg in monozygotic pairs.
CONCLUSIONS
The attenuation of the regression coefficient in the paired analysis provides support for the possibility that factors shared by twins contribute to the association between birthweight and blood pressure in singletons. Comparison of paired analysis in monozygotic and dizygotic pairs could not provide conclusive evidence for a role for genetic as opposed to shared environmental factors.
Topics: Adult; Birth Weight; Blood Pressure; Environment; Humans; Infant, Newborn; Twin Studies as Topic; Twins, Dizygotic; Twins, Monozygotic
PubMed: 15375085
DOI: 10.1093/ije/dyh260 -
BMC Pregnancy and Childbirth May 2023This review aimed to identify guidelines with recommendations applicable to the antenatal management of dichorionic diamniotic twin pregnancies within high-income...
OBJECTIVE
This review aimed to identify guidelines with recommendations applicable to the antenatal management of dichorionic diamniotic twin pregnancies within high-income countries, appraise their methodological quality, and discuss the similarities and variability across guidelines.
METHOD
A systematic literature review of electronic databases was performed. Manual searches of guideline repositories and websites of professional organisations were performed to identify additional guidelines. The protocol for this systematic review was registered on PROSPERO (CRD42021248586, 25 June 2021). AGREE II and AGREE-REX tools were applied to assess the quality of eligible guidelines. A narrative and thematic synthesis described and compared the guidelines and their recommendations.
RESULTS
Twenty-four guidelines were included, from which 483 recommendations were identified across 4 international organisations and 12 countries. Guidelines addressed eight themes and recommendations were classified accordingly: chorionicity and dating (103 recommendations), fetal growth (105 recommendations), termination of pregnancy (12 recommendations), fetal death (13 recommendations), fetal anomalies (65 recommendations), antenatal care (65 recommendations), preterm labour (56 recommendations) and birth (54 recommendations). Guidelines showed significant variability in recommendations, with conflicting recommendations regarding non-invasive preterm testing, definitions surrounding selective fetal growth restriction, screening for preterm labour and the timing of birth. Guidelines lacked a focus on standard antenatal management of DCDA twins, management of discordant fetal anomaly and single fetal demise.
CONCLUSIONS
Specific guidance for dichorionic diamniotic twins is overall indistinct and access to guidance regarding the antenatal management of these pregnancies is currently difficult. Management of discordant fetal anomaly or single fetal demise needs greater consideration.
Topics: Infant, Newborn; Pregnancy; Female; Humans; Pregnancy, Twin; Pregnancy Outcome; Fetal Death; Twins, Dizygotic; Obstetric Labor, Premature; Retrospective Studies
PubMed: 37179347
DOI: 10.1186/s12884-023-05652-z