Twin studies on cancer

Studies on cancer loci by use of twin data reveal sources of variation in risk. The Nordic twin and cancer registries contain the largest cohort of population representative twins ever studied with more than median 40 years of follow-up. This article considers findings that show influences on familial risk and demonstrates the strengths of the matched case co-twin design for unraveling important risk factors of cancers. Studies using twin data will expectedly continue to provide insights into cancer epidemiology and genetics for the benefit of prevention and treatment.

Case of twin achondroplasia and autism coexistence and literature review

Achondroplasia and autism spectrum disorder (ASD) are two genetically based disorders. The coexistence of autism with chromosomal abnormalities such as Down syndrome, monogenic syndromes such as tuberous sclerosis, Fragile X, and Rett syndrome, and microdeletion syndromes such as Phelan-McDermid syndrome helps to shed light on the genetic basis of autism spectrum disorder. The association between ASD and achondroplasia has been reported twice in the literature. In this article, we report Turkish patients who were born as identical twins from IVF pregnancy of 34 and 36-year-old parents, clinically and molecularly diagnosed with achondroplasia, and diagnosed with ASD at the age of 39 months. Our case is the first twin patient with the coexistence of achondroplasia and autism. We discuss environmental and genetic factors contributing to the development of ASD.

Long-term adverse neurodevelopmental outcomes of discordant twins delivered at term: A nationwide population-based study

OBJECTIVE

To evaluate long-term adverse neurodevelopmental outcomes of discordant twins delivered at term.

DESIGN

Retrospective cohort study.

SETTING

Nationwide (Republic of Korea).

POPULATION

All twin children delivered at term between 2007 and 2010.

METHODS

The study population was divided into two groups according to inter-twin birthweight discordancy: the 'concordant twin group', twin pairs with inter-twin birthweight discordancy less than 20%; and the 'discordant twin group', twin pairs with inter-twin birthweight discordancy of 20% or more. The risk of long-term adverse neurodevelopmental outcomes was compared between the concordant twin group and the discordant twin group. Long-term adverse neurodevelopmental outcomes between smaller and larger twin children within twin pairs were further analysed. The composite adverse neurodevelopmental outcome was defined as the presence of at least one of the following: motor developmental delay, cognitive developmental delay, autism spectrum disorders/attention deficit hyperactivity disorders, tics/stereotypical behaviour or epileptic/febrile seizure.

MAIN OUTCOME MEASURES

Long-term adverse neurodevelopmental outcome.

RESULTS

Of 22 468 twin children (11 234 pairs) included, 3412 (15.19%) twin children were discordant. The risk of composite adverse neurodevelopmental outcome was higher in the discordant twin group than in the concordant twin group (adjusted hazard ratio [HR] 1.13, 95% CI 1.03-1.24). The long-term adverse neurodevelopmental outcomes were not significantly different between smaller and larger twin children in discordant twin pairs (adjusted HR 1.01, 95% CI 0.81-1.28).

CONCLUSION

In twin pairs delivered at term, an inter-twin birthweight discordancy of 20% or greater was associated with long-term adverse neurodevelopmental outcomes; and long-term adverse neurodevelopmental outcomes were not significantly different in smaller or larger twin children in discordant twin pairs.

In search of environmental risk factors for obsessive-compulsive disorder: study protocol for the OCDTWIN project

BACKGROUND

The causes of obsessive-compulsive disorder (OCD) remain unknown. Gene-searching efforts are well underway, but the identification of environmental risk factors is at least as important and should be a priority because some of them may be amenable to prevention or early intervention strategies. Genetically informative studies, particularly those employing the discordant monozygotic (MZ) twin design, are ideally suited to study environmental risk factors. This protocol paper describes the study rationale, aims, and methods of OCDTWIN, an open cohort of MZ twin pairs who are discordant for the diagnosis of OCD.

METHODS

OCDTWIN has two broad aims. In Aim 1, we are recruiting MZ twin pairs from across Sweden, conducting thorough clinical assessments, and building a biobank of biological specimens, including blood, saliva, urine, stool, hair, nails, and multimodal brain imaging. A wealth of early life exposures (e.g., perinatal variables, health-related information, psychosocial stressors) are available through linkage with the nationwide registers and the Swedish Twin Registry. Blood spots stored in the Swedish phenylketonuria (PKU) biobank will be available to extract DNA, proteins, and metabolites, providing an invaluable source of biomaterial taken at birth. In Aim 2, we will perform within-pair comparisons of discordant MZ twins, which will allow us to isolate unique environmental risk factors that are in the causal pathway to OCD, while strictly controlling for genetic and early shared environmental influences. To date (May 2023), 43 pairs of twins (21 discordant for OCD) have been recruited.

DISCUSSION

OCDTWIN hopes to generate unique insights into environmental risk factors that are in the causal pathway to OCD, some of which have the potential of being actionable targets.

The Beginnings of Scientific Psychiatric Twin Research: Luxenburger's 1928 "Preliminary Report on the Psychiatric Examination of a Series of Twins"

While reports of twin pairs concordant for insanity began to appear in the 19th century, the first modern psychiatric twin study that fulfilled Galton's 1875 promise of the value of the twin method was published by the German Psychiatrist and Geneticist Hans Luxenburger in 1928. Luxenburger introduced four major methodological advances: the use of representative sampling, proband-wise concordance, rigorous zygosity diagnoses, and age correction. He used a narrow Kraepelinian diagnostic approach diagnosis and ascertained twins hospitalized, on a specific day, in all large Bavarian asylums. We include a brief biography of Luxenburger, summarize the findings of his paper and provide a full English translation in the appendix. Luxenburger presents evidence that the frequency of twinning in those with severe mental illness were as expected and reports proband-wise concordance for probable and definite dementia praecox (MZ-76%, DZ-0%) and manic-depressive insanity (MZ-75%, DZ-0%). He also examined eccentricity and hyperthymic or hypothymic personality in the dementia praecox and manic-depressive pairs, respectively. Luxenburger's substantial contributions to the history of psychiatric genetics should be considered in the context of his intimate but ambivalent relationship with the racial-hygiene policy of the German National Socialists.

Heritability of Dental Caries: Twin Studies

The study of twins is a powerful tool to infer the presence and amount of contribution of genetic variation to a particular trait or disease. The ability to compare identical or monozygotic twins with dizygotic twins permits the direct comparison of pairs of individuals that share 100% of their genomic DNA with pairs that share only 50%, with the assumption that these pairs are under the same environment. In the case of dental caries, the environment is same parents, under the same roof, with the same diet, oral hygiene habits, culture, and lifestyle. These data have consistently suggested that a relevant proportion of the variation of dental caries in populations is due to genetics.

Autism spectrum disorder and obstetric optimality: a twin study and meta-analysis of sibling studies

BACKGROUND

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with a strong genetic basis. Recent studies have suggested that its aetiology is also influenced by environmental factors. Some of the most examined environmental factors are obstetric complications. However, the results are inconsistent.

METHODS

We aimed to explore the association between obstetric complications and autism in a population-based twin sample using the Obstetric Enquiry Scale (OES), a scale that measures the presence or absence of pre-, peri- and neonatal factors. Additionally, we report the meta-analytic results for obstetrical factors reported in previously published sibling studies.

RESULTS

Our study included 115 cases pairs and 62 controls pairs and showed that children with autism and their unaffected co-twins present significantly more obstetric complications than controls (ASD vs. controls β 1.26, CI 95% 1.11-1.40 p < .001; unaffected co-twin vs. controls β 1.20, 95% CI 1.07-1.36 p < .003). However, we did not find statistically significant differences between children with ASD and their unaffected co-twins (β .96, 95% CI 0.85-1.09, p 0.55). Meta-analysis demonstrated that maternal hypertension (RR 1.35, CI 95% 1.23-1.48), uterine bleeding (RR 1.20 CI 95% 1.01-1.42) and exposure to antibiotic during pregnancy (1.11 CI 95% 1.00-1.22) increase risk of ASD.

CONCLUSIONS

This study confirms that children with ASD and their unaffected twins show more obstetric complications than controls. However, these complications do not distinguish between ASD twins and their unaffected co-twins. In addition, the meta-analysis showed little influence of birth factors on ASD which suggests a shared familial liability for both obstetric complications and autism, rather than a causal association.

Characterization of lip prints in a Portuguese twins' population

Lip print patterns are referred to as unique to each individual, but controversy exists surrounding twins. In this study, the lip prints of 19 pairs of monozygotic and 47 pairs of dizygotic twins were studied. The left lower lip was photographed and the furrows were classified using Renaud's classification. Results showed the same lip pattern was found only in one monozygotic pair (5.3%) and in 4 dizygotic pairs (8.5%), and no significant statistical differences were found between groups (p > 0.05). In monozygotic twins only type C furrows presence displayed statistical significant differences (p=0.034). As for dizygotic twins, there were statistical significant differences in the frequency of type A (p=0.005) and type G furrows (p=0.018). As for the most common types, both groups displayed a higher prevalence of vertical furrows (type B: 97.4% and 96.8%, type A: 86.8% and 87.2%, in monozygotic and dizygotic, respectively). The least frequent furrow type was type I and type E in monozygotic (2.6% and 5.3%, respectively) and types E, F and I, in dizygotic (6.4%, 7.4%. and 7.4%, respectively). Our results seem to point out that lip print patterns should be useful carefully in twins' identification.

Evidence of Bidirectional Associations Between Depressive Symptoms and Body Mass Among Older Adults

OBJECTIVES

Body fat, measured with body mass index (BMI), and obesity are associated with depressive symptoms. Among younger adults there is stronger evidence of obesity leading to depressive symptoms than of depressive symptoms leading to obesity, but the temporal relationship is unknown among older adults. This study utilized dual-change-score models (DCSMs) to determine the directional relationship between body mass and depressive symptoms among older adults.

METHOD

Participants (n = 1,743) from the Swedish Twin Registry (baseline age range 50-96 years) completed at least one assessment of BMI (nurse measurement of height and weight) and the Center for Epidemiologic Studies-Depression scale (CESD). More than half the sample completed 3 or more assessments, scheduled at intervals of 2-4 years. DCSMs modeled the relationship of BMI and CESD across age, both independently and as part of bivariate relationships.

RESULTS

Depressive symptoms contributed to subsequent changes in BMI after age 70, while BMI contributed to subsequent changes in depressive symptoms after age 82. Thus, there is a reciprocal relationship that may change with age. The effect was more pronounced for women.

DISCUSSION

The association of BMI and depressive symptoms is bidirectional among older adults, and it appears to be affected by both age and sex.

Adult Monozygotic Twins With Hypertrophic Cardiomyopathy and Identical Disease Expression and Clinical Course

A unique clinical circumstance involving middle-aged male identical twins with obstructive hypertrophic cardiomyopathy (HC) is reported. The concordance of morphologic (i.e., phenotype) findings and clinical course between the 2 patients is remarkable, including timing of the onset and progression of heart failure due to left ventricular outflow tract obstruction, frequency of paroxysmal atrial fibrillation and beneficial response to surgical myectomy and Cox-Maze IV procedure (performed 14 days apart). Histopathology of resected ventricular septal muscle showed identical hallmarks of HC including myocyte disorganization, small vessel disease, and myocardial fibrosis. A missense variant of the CRYAB gene was identified as potentially relevant to the pathogenesis of HC in the twins. Taken together, these observations support a powerful genetic determinant for the morphologic and clinical expression of HC, with little or no environmental influence.

Biallelic mutations in ABCB1 display recurrent reversible encephalopathy

The clinical phenotype linked with mutations in ABCB1, encoding P‐glycoprotein, has never been reported. Here, we describe twin sisters with biallelic mutations in ABCB1 who showed recurrent reversible encephalopathy accompanied by acute febrile or afebrile illness. Whole‐exome sequencing was performed on one of the twin and her healthy parents, and revealed compound heterozygous loss‐of‐function variants in ABCB1. The patient brains displayed substantial loss of xenobiotic clearance ability, as demonstrated by [¹¹C]verapamil positron emission tomography (PET) study, linking this phenotype with ABCB1 function. The endogenous cytokine clearance from the brain was also decreased in LPS‐treated ABCB1 knockout mice compared to controls. The results provide insights into the physiological requirement of ABCB1 in maintaining homeostasis of various compounds for normal brain function.

Type 2 diabetes in midlife and risk of cerebrovascular disease in late life: a prospective nested case-control study in a nationwide Swedish twin cohort

AIMS/HYPOTHESIS

We aimed to examine the association between midlife type 2 diabetes mellitus and cerebrovascular disease (CBD) in late life, and further to explore whether genetic and early-life familial environmental factors (such as shared childhood socioeconomic status and adolescent environment) play a role in this association.

METHODS

In this prospective nested case-control study based on the Swedish Twin Registry, 33,086 twin individuals who were born in 1958 or earlier and were CBD-free before the age of 60 were included. Midlife (40-59 years) type 2 diabetes was ascertained from self-report, the National Patient Registry (NPR) and glucose-lowering medication use. CBD diagnosis (cerebral infarction, occlusion of cerebral arteries, subarachnoid haemorrhage, intracerebral haemorrhage and unspecified CBD) and onset age were identified from the NPR. Late-life CBD was defined as CBD onset age ≥60 years. Generalised estimating equation (GEE) models were used to analyse unmatched case-control data (adjusted for the clustering of twins within a pair). Conditional logistic regression was used in co-twin matched case-control analyses in CBD-discordant twin pairs.

RESULTS

Of all the participants, 1248 (3.8%) had midlife type 2 diabetes and 3121 (9.4%) had CBD in late life. In GEE models adjusted for age, sex, education, BMI, smoking, alcohol consumption, marital status, hypertension and heart disease, the ORs (95% CIs) of type 2 diabetes were 1.29 (1.03, 1.61) for cerebral infarction, 2.03 (1.20, 3.44) for occlusion of cerebral arteries, 0.52 (0.12, 2.21) for subarachnoid haemorrhage and 0.78 (0.45, 1.36) for intracerebral haemorrhage. In multi-adjusted conditional logistic regression, the OR of the type 2 diabetes-cerebral infarction association was 0.96 (0.51, 1.80). The differences in ORs from the GEE and co-twin control analyses were not statistically significant (p = 0.780).

CONCLUSIONS/INTERPRETATION

Midlife type 2 diabetes is significantly associated with increased risk of cerebral infarction and occlusion of cerebral arteries, but not intracerebral haemorrhage or subarachnoid haemorrhage in late life. Genetic and early-life familial environmental factors do not appear to account for the type 2 diabetes-cerebral infarction association, but further clarification is needed.

Long-term treatment with eteplirsen in nonambulatory patients with Duchenne muscular dystrophy

This analysis aims to describe the outcomes of two nonambulatory patients with Duchenne muscular dystrophy (DMD) who participated in two clinical studies. The two consecutive trials of eteplirsen (studies 201 and 202) were conducted in patients with DMD (N = 12) and confirmed genetic mutations amenable to exon 51 skipping.In study 201, 12 patients were randomized to receive once-weekly, double-blind intravenous infusions of eteplirsen 30 or 50 mg/kg or placebo for 24 weeks; patients then received open-label eteplirsen during weeks 25 through 28. All 12 patients continued onto open-label extension study 202 and received long-term treatment with eteplirsen. We compared cardiac, pulmonary, and upper limb function and dystrophin production in the nonambulatory twin patients versus the 10 ambulatory patients through 240 combined treatment weeks.Ten study patients remained ambulatory through both studies, while the identical twin patients both experienced early, rapid loss of ambulation. The twin patients had greater disease severity at baseline (6-minute walk test [6MWT], 330 and 256 m) versus the other patients (n = 10; 6MWT range, 341-418 m). They maintained cardiac and upper limb function through combined week 240, with outcomes similar to those of the patients who remained ambulatory. Dystrophin production was confirmed following eteplirsen treatment.Despite the loss of ambulation, other markers of disease progression remained relatively stable in the eteplirsen-treated twin patients and were similar to those of the ambulatory patients.

Adrenal hypoplasia congenita in identical twins

We are presenting a monozygotic twin brothers presented at different ages with different presentations. Twin-A presented at age of 18 days with salt losing crisis. Investigations revealed high plasma renin with low-normal aldosterone. Adrenocorticotropic hormone, stimulation test revealed low 17-OH progesterone at 0 and 60 minutes. Adrenocorticotropic hormone level and serum cortisol were normal, which excluded initial impression of congenital adrenal hyperplasia. He was diagnosed to have isolated primary hypoaldosteronism. At age of 18 months, he was noticed to have hyperpigmentation of lips and gum. Adrenal failure was suspected, and hydrocortisone was added. Twin-B presented at 9 years and 6 months of age with adrenal crisis. Both were having unilateral undescended testes. Adrenal hypoplasia congenita (AHC) was suspected after his twin's presentation.  Molecular analysis for gene study for both of them revealed adrenal insufficiency, NR0B1 (DAX1) gene mutation. In conclusion, gene analysis is important for the diagnosis of AHC and for genetic counseling.

Genetically Informative Mediation Modeling Applied to Stressors and Personality-Disorder Traits in Etiology of Alcohol Use Disorder

A statistical mediation model was developed within a twin design to investigate the etiology of alcohol use disorder (AUD). Unlike conventional statistical mediation models, this biometric mediation model can detect unobserved confounding. Using a sample of 1410 pairs of Norwegian twins, we investigated specific hypotheses that DSM-IV personality-disorder (PD) traits mediate effects of childhood stressful life events (SLEs) on AUD, and that adulthood SLEs mediate effects of PDs on AUD. Models including borderline PD traits indicated unobserved confounding in phenotypic path coefficients, whereas models including antisocial and impulsive traits did not. More than half of the observed effects of childhood SLEs on adulthood AUD were mediated by adulthood antisocial and impulsive traits. Effects of PD traits on AUD 5‒10 years later were direct rather than mediated by adulthood SLEs. The results and the general approach contribute to triangulation of developmental origins for complex behavioral disorders.

Single-Cell Chromatin Modification Profiling Reveals Increased Epigenetic Variations with Aging

Post-translational modifications of histone proteins and exchanges of histone variants of chromatin are central to the regulation of nearly all DNA-templated biological processes. However, the degree and variability of chromatin modifications in specific human immune cells remain largely unknown. Here, we employ a highly multiplexed mass cytometry analysis to profile the global levels of a broad array of chromatin modifications in primary human immune cells at the single-cell level. Our data reveal markedly different cell-type- and hematopoietic-lineage-specific chromatin modification patterns. Differential analysis between younger and older adults shows that aging is associated with increased heterogeneity between individuals and elevated cell-to-cell variability in chromatin modifications. Analysis of a twin cohort unveils heritability of chromatin modifications and demonstrates that aging-related chromatin alterations are predominantly driven by non-heritable influences. Together, we present a powerful platform for chromatin and immunology research. Our discoveries highlight the profound impacts of aging on chromatin modifications.

A twin study exploring the association between childhood emotional and behaviour problems and specific psychotic experiences in a community sample of adolescents

BACKGROUND

Childhood emotional and behaviour problems are antecedents for later psychopathology. This study investigated genetic and environmental influences shaping the longitudinal association between childhood emotional and behaviour problems and specific PEs.

METHOD

In a community-based twin sample, parents reported on emotional and behaviour problems when twins were ages 7 and 12 years. At age 16 years, specific PEs were measured using self-reports and parent reports. Structural equation model-fitting was conducted.

RESULTS

Childhood emotional and behaviour problems were significantly associated with paranoia, cognitive disorganisation and parent-rated negative symptoms in adolescence (mean r = .15-.38), and to a lesser extent with hallucinations, grandiosity and anhedonia (mean r = .04-.12). Genetic influences on childhood emotional and behaviour problems explained significant proportions of variance in adolescent paranoia (4%), cognitive disorganisation (8%) and parent-rated negative symptoms (3%). Unique environmental influences on childhood emotional and behaviour problems explained ≤1% of variance in PEs. Common environmental influences were only relevant for the relationship between childhood emotional and behaviour problems and parent-rated negative symptoms (explaining 28% of variance) and are partly due to correlated rater effects.

CONCLUSIONS

Childhood emotional and behaviour problems are significantly, if weakly, associated with adolescent PEs. These associations are driven in part by common genetic influences underlying both emotional and behaviour problems and PEs. However, psychotic experiences in adolescence are largely influenced by genetic and environmental factors that are independent of general childhood emotional and behaviour problems, suggesting they are not merely an extension of childhood emotional and behaviour problems.

Association of Raynaud's phenomenon with a polymorphism in the NOS1 gene

Background

Raynaud’s phenomenon (RP) describes the phenomenon of recurrent vasospasm of digital arteries, associated with skin colour changes: pallor, cyanosis and erythema. Twin studies have indicated a genetic predisposition for RP; however, the precise aetiology of RP remains unknown. It is thought that genetic variation in temperature-responsive or vasospastic genes might underlie RP so performed a candidate gene study in a large, population based sample. We assessed the association between RP and single nucleotide polymorphisms (SNPs) in the TRPA1, TRPM8, CALCA, CALCB and NOS1 genes.

Methods

Analysis included a total of 4276 individuals from the TwinsUK database. RP status had been determined using validated, self-administered questionnaires and was diagnosed in 640 individuals (17.6%). 66 tag SNPs across the candidate genes were tested for association with RP status using a linear regression model, accounting for covariates. Adjustment was made for multiple testing. RegulomeDB and GTEx databases were used to assess possible functional effects of the polymorphisms.

Results

Nominally significant associations between RP and four SNPs in NOS1 and one in CALCB were identified. After permutation testing, rs527590 SNP in NOS1 passed the significance threshold. RegulomeDB scores indicated an unlikely functional effect of this variant, while the survey of the GTEx database found the SNP and several variants in linkage disequilibrium to be cis-eQTLs in skin.

Conclusion

Results indicate that RP is associated with variation in gene NOS1. This finding may be related to the observation that the significant SNP in NOS1 is known to exhibit functional influence on the gene expression.

A proton MR spectroscopy study of the thalamus in twins with autism spectrum disorder

Multiple lines of research have reported thalamic abnormalities in individuals with autism spectrum disorder (ASD) that are associated with social communication impairments (SCI), restricted and repetitive behaviors (RRB), or sensory processing abnormalities (SPA). Thus, the thalamus may represent a common neurobiological structure that is shared across symptom domains in ASD. Same-sex monozygotic (MZ) and dizygotic (DZ) twin pairs with and without ASD underwent cognitive/behavioral evaluation and magnetic resonance imaging to assess the thalamus. Neurometabolites were measured with 1H magnetic resonance spectroscopy (MRS) utilizing a multi-voxel PRESS sequence and were referenced to creatine+phosphocreatine (tCr). N-acetyl aspartate (NAA), a marker of neuronal integrity, was reduced in twins with ASD (n=47) compared to typically-developing (TD) controls (n=33), and this finding was confirmed in a sub-sample of co-twins discordant for ASD (n=11). NAA in the thalamus was correlated to a similar extent with SCI, RRB, and SPA, such that reduced neuronal integrity was associated with greater symptom severity. Glutamate+glutamine (Glx) was also reduced in affected versus unaffected co-twins. Additionally, NAA and Glx appeared to be primarily genetically-mediated, based on comparisons between MZ and DZ twin pairs. Thus, thalamic abnormalities may be influenced by genetic susceptibility for ASD but are likely not domain-specific.

Metabolomic markers of fatigue: Association between circulating metabolome and fatigue in women with chronic widespread pain

BACKGROUND

Fatigue is a sensation of unbearable tiredness that frequently accompanies chronic widespread musculoskeletal pain (CWP) and inflammatory joint disease. Its mechanisms are poorly understood and there is a lack of effective biomarkers for diagnosis and onset prediction. We studied the circulating metabolome in a population sample characterised for CWP to identify biomarkers showing specificity for fatigue.

MATERIAL AND METHODS

Untargeted metabolomic profiling was conducted on fasting plasma and serum samples of 1106 females with and without CWP from the TwinsUK cohort. Linear mixed-effects models accounting for covariates were used to determine relationships between fatigue and metabolites. Receiver operating curve (ROC)-analysis was used to determine predictive value of metabolites for fatigue.

RESULTS

While no association between fatigue and metabolites was identified in twins without CWP (n=711), in participants with CWP (n=395), levels of eicosapentaenoate (EPA) ω-3 fatty acid were significantly reduced in those with fatigue (β=-0.452±0.116; p=1.2×10-4). A significant association between fatigue and two other metabolites also emerged when BMI was excluded from the model: 3-carboxy-4-methyl-5-propyl-2-furanpropanoate (CMPF), and C-glycosyltryptophan (p=1.5×10-4 and p=3.1×10-4, respectively). ROC analysis has identified a combination of 15 circulating metabolites with good predictive potential for fatigue in CWP (AUC=75%; 95% CI 69-80%).

CONCLUSION

The results of this agnostic metabolomics screening show that fatigue is metabolically distinct from CWP, and is associated with a decrease in circulating levels of EPA. Our panel of circulating metabolites provides the starting point for a diagnostic test for fatigue in CWP.

Inequality in genetic cancer risk suggests bad genes rather than bad luck

Heritability is often estimated by decomposing the variance of a trait into genetic and other factors. Interpreting such variance decompositions, however, is not straightforward. In particular, there is an ongoing debate on the importance of genetic factors in cancer development, even though heritability estimates exist. Here we show that heritability estimates contain information on the distribution of absolute risk due to genetic differences. The approach relies on the assumptions underlying the conventional heritability of liability model. We also suggest a model unrelated to heritability estimates. By applying these strategies, we describe the distribution of absolute genetic risk for 15 common cancers. We highlight the considerable inequality in genetic risk of cancer using different metrics, e.g., the Gini Index and quantile ratios which are frequently used in economics. For all these cancers, the estimated inequality in genetic risk is larger than the inequality in income in the USA.

Design and Implementation of a Tactile Stimulation Device to Increase Auditory Discrimination

Reading is a complex process that requires various simultaneous brain processes. One of the most common types of reading disorders is developmental dyslexia, and one of the objectives of speech therapy sessions for children with developmental dyslexia is to increase their auditory discrimination. One of the most commonly used Auditory Discrimination Tests (ADTs) is Wepman's  Auditory Discrimination Test (WADT). It includes minimal pair words categorized by characteristics of vowels and consonants. The goal of this research is to design and implement a tactile stimulation device based on Wepman's test to increase auditory discrimination in children with developmental dyslexia in therapy sessions, so that while playing each word for the children, vibrational cues are presented to their left palm and fingers. The vibrational cues provided by 23 vibration motors can notify the child of the difference or similarity between the words. First, the device was evaluated by being applied on six female participants aged 6 to 8 with no hearing disabilities and no developmental dyslexia. Scores obtained from the healthy children showed that they can perceive the tactile function of the device. Then, function of the device was tested on 8-year-old twin girls with developmental dyslexia. The test was conducted as a controlled experiment. One of the twins participated in speech therapy treatment, while the other practiced with the device. During the study, three sessions were allocated to determine the baseline of auditory discrimination, three sessions to the intervention, and two sessions (the first, one week and the second, three weeks after the intervention sessions) to determine the children's auditory discrimination (follow-up). The analysis of trend variations and changes in mean showed that both the speech therapy and the intervention based on practicing with the device were effective in increasing children's auditory discrimination (Percentage of Non-overlapping Data = 100%). The results were stable three weeks after the intervention sessions. Therefore, using the device in speech therapy sessions can be useful and effective in improving auditory discrimination.

Twin Hearts in Identical Twins

Cardiac manifestations and angiographic characteristics of coronary artery disease in identical twins have been previously dealt with in a handful of case reports and series; yet, the results were highly controversial. Our rare case demonstrates striking similarities in both the timing and type of clinical manifestation, as well as in the underlying anatomy and the distribution of coronary artery disease. When premature coronary artery disease is found in one of a monozygotic twin pair, evaluating the other twin is a reasonable approach.

Attention Deficit Hyperactivity Disorder Symptoms and Low Educational Achievement: Evidence Supporting A Causal Hypothesis

Attention Deficit Hyperactivity Disorder (ADHD) and educational achievement are negatively associated in children. Here we test the hypothesis that there is a direct causal effect of ADHD on educational achievement. The causal effect is tested in a genetically sensitive design to exclude the possibility of confounding by a third factor (e.g. genetic pleiotropy) and by comparing educational achievement and secondary school career in children with ADHD who take or do not take methylphenidate. Data on ADHD symptoms, educational achievement and methylphenidate usage were available in a primary school sample of ~10,000 12-year-old twins from the Netherlands Twin Register. A substantial group also had longitudinal data at ages 7-12 years. ADHD symptoms were cross-sectionally and longitudinally, associated with lower educational achievement at age 12. More ADHD symptoms predicted a lower-level future secondary school career at age 14-16. In both the cross-sectional and longitudinal analyses, testing the direct causal effect of ADHD on educational achievement, while controlling for genetic and environmental factors, revealed an association between ADHD symptoms and educational achievement independent of genetic and environmental pleiotropy. These findings were confirmed in MZ twin intra-pair differences models, twins with more ADHD symptoms scored lower on educational achievement than their co-twins. Furthermore, children with ADHD medication, scored significantly higher on the educational achievement test than children with ADHD who did not use medication. Taken together, the results are consistent with a direct causal effect of ADHD on educational achievement.

Etiological influences on the stability of autistic traits from childhood to early adulthood: evidence from a twin study

BACKGROUND

Autism spectrum disorders (ASD) are persistent and lifelong conditions. Despite this, almost all twin studies focus on childhood. This twin study investigated the stability of autistic traits from childhood to early adulthood and explored the degree to which any stability could be explained by genetic or environmental factors.

METHODS

Parents of over 2500 twin pairs completed questionnaires assessing autistic traits when twins were aged either 9 or 12 years and again when twins were aged 18. Bivariate twin analysis assessed the degree of phenotypic and etiological stability in autistic traits across this period. Genetic overlap in autistic traits across development was also tested in individuals displaying a broad ASD phenotype, defined as scoring within the highest 5% of the sample.

RESULTS

Autistic traits displayed moderate phenotypic stability (r = .39). The heritability of autistic traits was 76-77% in childhood and 60-62% in adulthood. A moderate degree of genetic influences on childhood autistic traits were carried across into adulthood (genetic correlation = .49). The majority (85%) of the stability in autistic traits was attributable to genetic factors. Genetic influences on autistic traits were moderately stable from childhood to early adulthood at the extremes (genetic correlation = .64).

CONCLUSIONS

Broad autistic traits display moderate phenotypic and etiological stability from childhood to early adulthood. Genetic factors accounted for almost all phenotypic stability, although there was some phenotypic and etiological instability in autistic traits. Thus, autistic traits in adulthood are influenced by a combination of enduring and unique genetic factors.

[Selective feticide in monochorionic twin pregnancies with discordant fetal anomalies: management and outcome]

OBJECTIVE

To analyze results and outcome after selective feticide for discordant anomalies in monochorionic twins.

DESIGN

Prospective cohort study.

SETTING

Fetal medicine center, Institute for the Care of Mother and Child, Praha.

METHODS

Analysis of outcome of monochorionic pregnancies after intrauterine surgery for structural abnormalities between January 2013 and June 2016.

RESULTS

We performed 13 intrauterine operations in monochorionic twins with structural anomalies during the period. There were 12 monochorionic diamniotic and one monochorionic monoamniotic twins. We encountered four cases of Twin Reversed Arterial Perfusion sequence (TRAP), six central nervous system lesions, two abdominal wall defects and one heterokaryotypic pregnancy with trisomy 13. In seven cases we performed bipolar cord occlusion, in four cases of TRAP sequence we performed radiofrequency ablation (RFA). We also performed laser photocoagulation of placental anastomoses in a case of gastroschisis complicated with twin-to-twin transfusion syndrome. One operation was unsuccessful for technical reasons - failing to perform amnioinfusion in a fetus with eventeration and anhydramnios. All procedures were performed in local anesthesia. Fetuses were born between 26 a 41 weeks of gestation (mean 35 weeks; 77% of fetuses were delivered after 32 weeks). Mean neonatal weight 2260 g. We encountered no intrauterine demise of a healthy fetus.

CONCLUSION

Patients with discordant fetal anomalies in monochorionic twins can be offered a selective feticide via bipolar umbilical cord occlusion or radiofrequency ablation that are proven to be safe and effective.

[Maple syrup urine disease and gene mutations in twin neonates]

OBJECTIVE

To investigate the clinical features of one pair of twin neonates with maple syrup urine disease (MSUD) in the Chinese Han population and pathogenic mutations in related genes, and to provide guidance for the early diagnosis and treatment of MSUD.

METHODS

The clinical and imaging data of the twin neonates were collected. The peripheral blood samples were collected from the twin neonates and their parents to detect the genes related to MSUD (BCKDHA, BCKDHB, DBT, and DLD). The loci with gene mutations were identified, and a bioinformatic analysis was performed.

RESULTS

Two mutations were detected in the BCKDHB gene, missense mutation c.304G>A (p.Gly102Arg) and nonsense mutation c.331C>T (p.Arg111*), and both of them were heterozygotes. The mutation c.304G>A (p.Gly102Arg) had not been reported in the world. Their father carried the missense mutation c.304G>A (p.Gly102Arg), and their mother carried the nonsense mutation c.331C>T (p.Arg111*).

CONCLUSIONS

The c.331C>T (p.Arg111*) heterozygous mutation in BCKDHB gene is the pathogenic mutation in these twin neonates and provides a genetic and molecular basis for the clinical features of children with MSUD.

Shared Etiology of Psychotic Experiences and Depressive Symptoms in Adolescence: A Longitudinal Twin Study

Psychotic disorders and major depression, both typically adult-onset conditions, often co-occur. At younger ages psychotic experiences and depressive symptoms are often reported in the community. We used a genetically sensitive longitudinal design to investigate the relationship between psychotic experiences and depressive symptoms in adolescence. A representative community sample of twins from England and Wales was employed. Self-rated depressive symptoms, paranoia, hallucinations, cognitive disorganization, grandiosity, anhedonia, and parent-rated negative symptoms were collected when the twins were age 16 (N = 9618) and again on a representative subsample 9 months later (N = 2873). Direction and aetiology of associations were assessed using genetically informative cross-lagged models. Depressive symptoms were moderately correlated with paranoia, hallucinations, and cognitive disorganization. Lower correlations were observed between depression and anhedonia, and depression and parent-rated negative symptoms. Nonsignificant correlations were observed between depression and grandiosity. Largely the same genetic effects influenced depression and paranoia, depression and hallucinations, and depression and cognitive disorganization. Modest overlap in environmental influences also played a role in the associations. Significant bi-directional longitudinal associations were observed between depression and paranoia. Hallucinations and cognitive disorganization during adolescence were found to impact later depression, even after controlling for earlier levels of depression. Our study shows that psychotic experiences and depression, as traits in the community, have a high genetic overlap in mid-adolescence. Future research should test the prediction stemming from our longitudinal results, namely that reducing or ameliorating positive and cognitive psychotic experiences in adolescence would decrease later depressive symptoms.

Neonatal antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a clinical entity characterized by arterial and venous thrombosis, adverse obstetric outcome and the presence of antibodies against phospholipids in serum or plasma. The objective of the present study is to describe a rare case of APS that occurred in a neonate born from a patient previously diagnosed as primary APS. A male, preterm born twin infant, whose mother had been diagnosed as primary APS, developed thrombocytopenia, livedo reticularis, pericardial effusion and thrombosis of the left subclavian and external jugular veins concomitantly with severe respiratory tract infection soon after his delivery, that culminated with his death two months after the birth, in spite of the large spectrum antibiotic therapy and all supportive measures. Laboratory findings included high titers of IgM anticardiolipin antibodies and moderate titers of IgG isotype and negative antinuclear antibody, configuring a case of neonatal APS. Neonatal APS is a rare clinical condition, with only a few cases described in the literature. Its occurrence may depend on the passage of antibodies through the placenta or, as it seems to have occurred in the present case, by the production of de novo antibodies by the fetus. The present case illustrates the necessity of a higher surveillance of the neonates born from mothers with primary APS or systemic lupus erythematosus (SLE) for the eventual development of such complication.

Endometriosis and Glanzmann’s thrombasthenia

Glanzmann’s thrombasthenia (GT) is a rare bleeding syndrome characterized by deficiency or defect of platelet aggregation complex. The pathogenesis of endometriosis is controversial but the strongest evidence leans towards retrograde menstruation. GT probably predisposes to endometriosis. The management of women affected by this disease can be difficult due to the risk of bleeding complications, especially during surgical treatment. We describe the cases of three sisters affected by endometriosis and GT, referred to our Department, who received different therapeutic management.

Adult-Onset Hemiplegic Migraine with Cortical Enhancement and Oedema

We present genetically identical twin patients who experienced late-onset migraine with visual and somatosensory auras and later developed hemiplegic migraines associated with severe cortical oedema and enhancement. Both positron emission tomography and electroencephalography showed an increase in activity contralateral to the hemiplegic side. Brain biopsy during the attack showed reactive astrogliosis and microgliosis. Mutations in CACNA1A, ATP1A2, SLC1A3 and NOTCH3 were ruled out by sequencing. This report shows the clinical and genetic evaluation of a severe form of familial hemiplegic migraine as well as the evolution of the imaging changes.

Airway Compression by Major Aortopulmonary Collaterals with 22q11 Deletion

Hypoxic choking episodes due to airway obstruction occurred frequently from 4 months of age in a boy with 22q11 deletion, pulmonary atresia, ventricular septal defect, absent central pulmonary artery, tracheobronchomalacia, and an aberrant right tracheal bronchus. The tracheobronchial tree was compressed by a posteriorly displaced ascending aorta and right aortic arch with aberrant left subclavian artery and major aortopulmonary collateral arteries. Single-stage unifocalization and intracardiac repair plus aortopexy at 8 months resulted in resolution of the respiratory distress and heart failure.

What Is Not in the Name? Dopa-Responsive Dystonia May Respond to More Than L-Dopa

BACKGROUND

Classic L-dopa-responsive dystonia is characterized by the triad of dystonia, diurnal fluctuation of signs, and dramatic response of signs to low-dose L-dopa therapy. Dopa-responsive dystonia succinctly summarizes the relevant clinical features. However, literal application of this label or consideration of dopa-responsive dystonia as a diagnostic end without molecular and/or biochemical definition may contribute to misdiagnosis and incomplete treatment in dopa-responsive conditions that impair synthesis of monoamine neurotransmitters besides dopamine.

PATIENT DESCRIPTION

We describe and provide video for twin patients with a rare form of dopa-responsive dystonia due to sepiapterin reductase deficiency. As is typical in dopa-responsive dystonia, these patients displayed dramatic improvement with L-dopa/carbidopa therapy. However, treatment was suboptimal until 5-hydroxytryptophan was added to address their serotonergic deficit.

DISCUSSION

Our report highlights the limitations of the dopa-responsive dystonia label and increases awareness of sepiapterin reductase deficiency and other conditions that may present as dopa-responsive dystonia. We provide a diagnostic and therapeutic approach to guide the clinician in evaluating and treating individuals with dopa-responsive dystonia.

Multidimensional assessment of impulsivity in schizophrenia, bipolar disorder, and major depressive disorder: testing for shared endophenotypes

BACKGROUND

Impulsivity is associated with bipolar disorder as a clinical feature during and between manic episodes and is considered a potential endophenotype for the disorder. Schizophrenia and major depressive disorder share substantial genetic overlap with bipolar disorder, and these two disorders have also been associated with elevations in impulsivity. However, little is known about the degree of overlap among these disorders in discrete subfacets of impulsivity and whether any overlap is purely phenotypic or due to shared genetic diathesis.

METHOD

We focused on five subfacets of impulsivity: self-reported attentional, motor, and non-planning impulsivity, self-reported sensation seeking, and a behavioral measure of motor inhibition (stop signal reaction time; SSRT). We examined these facets within and across disorder proband and co-twin groups, modeled heritability, and tested for endophenotypic patterning in a sample of twin pairs recruited from the Swedish Twin Registry (N = 420).

RESULTS

We found evidence of moderate to high levels of heritability for all five subfacets. All three proband groups and their unaffected co-twins showed elevations on attentional, motor, and non-planning impulsivity. Schizophrenia probands (but not their co-twins) showed significantly lower sensation seeking, and schizophrenia and bipolar disorder probands (but not in their co-twins) had significantly longer SSRTs, compared with healthy controls and the other groups.

CONCLUSIONS

Attentional, motor, and non-planning impulsivity emerged as potential shared endophenotypes for the three disorders, whereas sensation seeking and SSRT were associated with phenotypic affection but not genetic loading for these disorders.

Congenital Kyphoscoliosis in Monozygotic Twins: Ten-Year Follow-up Treated by Posterior Vertebral Column Resection (PVCR): A Case Report

The etiology of congenital scoliosis and its development remains unclear and has not yet been fully identified, even there are theories that congenital scoliosis could be derived from the failure of formation or failure of segmentation, which are etiologically heterogeneous with genetic, epigenetic, and environmental factors contributing to their occurrence. We reported a case of long-term follow-up after posterior vertebral column resection (PVCR) in both identical twins with similar congenital kyphoscoliosis at thoracolumbar levels. Twin I had been noticed by his parents to have asymmetry of his back at age 5 years, but no treatment was given. Twin II was first noticed to have a spinal problem at 11 years of age by his parents. Overtime, spine of both twins became further deviated to the left with kyphosis and was referred to our hospital. Both monozygotic twins were treated by PVCR and satisfactory results were demonstrated at 10-year follow-up.This case is the first report on the surgical treatment with PVCR, almost simultaneously, in both identical twins who had similar congenital vertebral anomalies causing kyphoscoliosis. Both identical twins with congenital kyphoscoliosis had undergone surgical correction by PVCR, anterior support with a mesh cage and posterior fusion using pedicle screws at the age of 14 years and achieved a satisfactory correction and a stable spine without curve progression with 10-year follow-up.

Genetic and Environmental Regulation on Longitudinal Change of Metabolic Phenotypes in Danish and Chinese Adult Twins

OBJECTIVE

The rate of change in metabolic phenotypes can be highly indicative of metabolic disorders and disorder-related modifications. We analyzed data from longitudinal twin studies on multiple metabolic phenotypes in Danish and Chinese twins representing two populations of distinct ethnic, cultural, social-economic backgrounds and geographical environments.

MATERIALS AND METHODS

The study covered a relatively large sample of 502 pairs of Danish adult twins followed up for a long period of 12 years with a mean age at intake of 38 years (range: 18-65) and a total of 181 Chinese adult twin pairs traced for about 7 years with a mean baseline age of 39.5 years (range: 23-64). The classical twin models were fitted to the longitudinal change in each phenotype (Δphenotype) to estimate the genetic and environmental contributions to the variation in Δphenotype.

RESULTS

Moderate to high contributions by the unique environment were estimated for all phenotypes in both Danish (from 0.51 for low density lipoprotein cholesterol up to 0.72 for triglycerides) and Chinese (from 0.41 for triglycerides up to 0.73 for diastolic blood pressure) twins; low to moderate genetic components were estimated for long-term change in most of the phenotypes in Danish twins except for triglycerides and hip circumference. Compared with Danish twins, the Chinese twins tended to have higher genetic control over the longitudinal changes in lipids (except high density lipoprotein cholesterol) and glucose, higher unique environmental contribution to blood pressure but no genetic contribution to longitudinal change in body mass traits.

CONCLUSION

Our results emphasize the major contribution of unique environment to the observed intra-individual variation in all metabolic phenotypes in both samples, and meanwhile reveal differential patterns of genetic and common environmental regulation on changes over time in metabolic phenotypes across the two samples.

Long-Term Trajectories of PTSD in Vietnam-Era Veterans: The Course and Consequences of PTSD in Twins

We estimated the temporal course of posttraumatic stress disorder (PTSD) in Vietnam-era veterans using a national sample of male twins with a 20-year follow-up. The complete sample included those twins with a PTSD diagnostic assessment in 1992 and who completed a DSM-IV PTSD diagnostic assessment and a self-report PTSD checklist in 2012 (n = 4,138). Using PTSD diagnostic data, we classified veterans into 5 mutually exclusive groups, including those who never had PTSD, and 4 PTSD trajectory groups: (a) early recovery, (b) late recovery, (c) late onset, and (d) chronic. The majority of veterans remained unaffected by PTSD throughout their lives (79.05% of those with theater service, 90.85% of those with nontheater service); however, an important minority (10.50% of theater veterans, 4.45% of nontheater veterans) in 2012 had current PTSD that was either late onset (6.55% theater, 3.29% nontheater) or chronic (3.95% theater, 1.16% nontheater). The distribution of trajectories was significantly different by theater service (p < .001). PTSD remains a prominent issue for many Vietnam-era veterans, especially for those who served in Vietnam.

Differential methylation in inflammation and type 2 diabetes genes in siblings born before and after maternal bariatric surgery

OBJECTIVE

Siblings born before (BMS) and after (AMS) maternal biliopancreatic diversion (BPD) show differences in the methylome. The objective was to use a sibling-pair design to examine the effects from interpregnancy weight loss as a consequence of maternal bariatric surgery, other than BPD, on the methylome comparing BMS and AMS.

METHODS

Women with at least one child born before and one after bariatric surgery were identified in Swedish national registers. Whole blood samples from BMS (N = 31) and AMS (N = 31) siblings were collected for epigenetic methylation analysis while maternal information was collected from antenatal medical records.

RESULTS

In total 3,074 genes, with corresponding 23,449 CpG methylation sites, were differently methylated and associated with an overrepresentation of differently methylated CpG sites in genes involved with insulin receptor signaling, type 2 diabetes signaling, and leptin signaling in obesity, while the most significant differently methylated genes were HLA-DQA1, HLA-DQB1, and TSPAN18, when comparing BMS and AMS siblings.

CONCLUSIONS

These results suggest that maternal bariatric surgery, with subsequent weight loss between pregnancies, is associated with alterations in the methylome of genes involved in insulin receptor signaling, type 2 diabetes signaling, and leptin signaling in obesity in a comparison of BMS and AMS siblings.

[Variability in the clinical presentation of Pompe disease: development following enzyme replacement therapy]

INTRODUCTION

Pompe disease is a generalized progressive disease caused by a deficiency of the lysosome enzyme acid alpha-glucosidase (GAA). We present three cases with different clinical symptomatology and treated with enzyme replacement therapy (ERT) with positive evolution.

CASE REPORTS

Case 1: three-month old male, with weakness and rejecting meals; mild hepatomegaly, discrete macroglossia and muscular hypotony; and increased muscular enzymes. Case 2: five-month old male, with delayed motor development, severe neurosensory deafness, and respiratory disorder of difficult evolution; muscular hypotony; and mild increase in creatine kinase. Case 3: 22-year old male, with progressive dyspnea, with history of increased creatine kinase and transaminases, and hypercholesterolemia. He suffered from severe respiratory failure requiring endotraqueal intubation Muscular biopsy showed glycogen storage suggestive of Pompe disease. In the three cases, the EMG showed a characteristic pattern with pseudomyotonic discharges and the deficiency in GAA was confirmed in lymphocytes. One single mutation was observed in one case and two in the other two cases. Every patient received ERT showing a favorable evolution; with disappearance of cardiac disorders in case 1, improvement in motor development in both infants and no longer need for mechanical ventilation in case 3.

CONCLUSION

Pompe disease has a wide variability in clinical expression. ERT achieves a good response, especially in infant forms of the disease. The survival of treated patients with these Pompe disease forms will allow knowing further the course of the disease.