A novel nonsense PKD1L1 variant cause heterotaxy syndrome with congenital asplenia in a Han Chinese patient.

Heterotaxy syndrome is a very rare congenital disease, which is caused by the disorder of left-right asymmetry during visceral development. However, pathogenic genetic lesions are found in less than 20% of HS patients. In this cohort study, whole-exome sequencing was performed for 110 patients with situs inversus or situs ambiguous. We identified a novel nonsense variant in PKD1L1(c.1387 C > T; p.463Gln*) in a Chinese patient with heterotaxy syndrome and congenital asplenia. This homozygous variant caused the domain of PKD1L1 complete absence. To our knowledge, this novel variant is the first phenotype of congenital asplenia found in patients with PKD1L1 variants, and the first PKD1L1 variant found in China. Our findings expand the spectrum of PKD1L1 variants and provide support for PKD1L1 variant and congenital asplenia, and the critical role of PKD1L1 during left-right patterning in the Han Chinese population.

DNAH11 compound heterozygous variants cause heterotaxy and congenital heart disease.

Heterotaxy (HTX), a condition characterized by internal organs not being arranged as expected relative to each other and to the left-right axis, is often accompanied with congenital heart disease (CHD). The purpose was to detect the pathogenic variants in a Chinese family with HTX and CHD. A non-consanguineous Han Chinese family with HTX and CHD, and 200 unrelated healthy subjects were enlisted. Exome sequencing and Sanger sequencing were applied to identify the genetic basis of the HTX family. Compound heterozygous variants, c.3426-1G>A and c.4306C>T (p.(Arg1436Trp)), in the dynein axonemal heavy chain 11 gene (DNAH11) were identified in the proband via exome sequencing and further confirmed by Sanger sequencing. Neither c.3426-1G>A nor c.4306C>T variant in the DNAH11 gene was detected in 200 healthy controls. The DNAH11 c.3426-1G>A variant was predicted as altering the acceptor splice site and most likely affecting splicing. The DNAH11 c.4306C>T variant was predicted to be damaging, which may reduce the phenotype severity. The compound heterozygous variants, c.3426-1G>A and c.4306C>T, in the DNAH11 gene might be the pathogenic alterations resulting in HTX and CHD in this family. These findings broaden the variant spectrum of the DNAH11 gene and increase knowledge used in genetic counseling for the HTX family.

Right atrial isomerism diagnosed by STIC-HD live flow and autopsy: A case report.

RATIONALE: Right atrial isomerism (RAI) is one of the most severe forms of congenital heart disease. This case of RAI was so complex that it incorporated 7 heart defects. It can be challenging to display the spatial relationship between different anatomical structures using conventional two-dimensional and color ultrasound (2D-Doppler imaging); therefore, we used spatio-temporal image correlation (STIC) and high definition live flow imaging technology to vividly display this case of RAI in a stereoscopic mode. PATIENT CONCERNS: A 24-year-old woman was referred to our tertiary center at 24 weeks of gestation. The woman had difficult conceiving. Once pregnant, she was opposed to abortion, even if there was a possibility of deformity. DIAGNOSIS: The fetus presented with an atrioventricular septal defect, persistent left superior vena cava, supra-cardiac total anomalous pulmonary venous connection (TAPVC), double outlet right ventricle, right ductus arteriosus, right aortic arch (RAA) with mirror image branching, and aortic arch dysplasia. INTERVENTIONS: After consulting a pediatric cardiologist, the woman requested an abortion and consented to an autopsy. OUTCOMES: Autopsy supported the echocardiographic findings. LESSONS: Accurate diagnosis of RAI is essential for clinical and parent decision making. 2D-Doppler imaging combined with STIC-HD live flow can be used to visualize the spatial morphology of blood vessels, including the cardiac chambers and great vessels of the fetal heart, and smaller peripheral vessels.

A novel heterotaxy gene: Expansion of the phenotype of TTC21B-spectrum disease.

TTC21B encodes the protein IFT139, a critical component of the retrograde transport system within the primary cilium. Biallelic, pathogenic TTC21B variants are associated with classic ciliopathy syndromes, including nephronophthisis, Jeune asphyxiating thoracic dystrophy, and Joubert Syndrome, with ciliopathy-spectrum traits such as biliary dysgenesis, primary ciliary dyskinesia, and situs inversus, and also with focal segmental glomerulosclerosis. We report a 9-year-old male with focal segmental glomerulosclerosis requiring kidney transplant, primary ciliary dyskinesia, and biliary dysgenesis, found by research-based exome sequencing to have biallelic pathogenic TTC21B variants. A sibling with isolated heterotaxy was found to harbor the same variants. This case highlights the phenotypic spectrum and unpredictable manifestations of TTC21B-related disease, and also reports the first association between TTC21B and heterotaxy, nominating TTC21B as an important new heterotaxy gene.

A Case Report of Left Atrial Isomerism in a Syndromic Context.

The objective of our paper is to underline the importance of assessing microarray genetic analysis for the detection of chromosomal abnormalities in rare cases such as left atrial isomerism, mostly in the context of antenatally detected syndromes. We present the case of a 26-year-old primipara, at 26 weeks of gestation, with prior first trimester normal anomaly scan, who presented in our department accusing lower abdominal pain. An anomaly ultrasound examination of the fetus revealed cardiomegaly with increased size of the right atrium, non-visualization of the atrial septum or the foramen ovale, malalignment of the three-vessel view, location of the superior vena cava above the two-vessel view, slight pericardial effusion, and no interruption of the inferior vena cava nor presence of azygos vein being noted. Associated extracardiac abnormalities, such as small kidneys at the level of the iliac fossa, micrognathia, dolichocephaly with hypoplasia of the cerebellum, increased nuchal fold, and reduced fetal movements were also reported. A diagnostic amniocentesis was performed, and, while the conventional rapid prenatal diagnostic test of the multiplex quantitative fluorescent polymerase chain reaction (PCR) came as normal, the microarray analysis (ChAS, NCBI Built 37 hg 19, detection of microdeletions or microduplications larger than 100 kb) revealed two chromosomal abnormalities: a 22.84 Mb loss of genetic material in the 18q21.31-18q23 chromosomal region and a gain of 22.31 Mb of genetic material in the 20p13-20p11.21 chromosomal region. After the termination of pregnancy, a necropsy of the fetus was performed, confirming heterotaxy syndrome with a common atrium, no atrial septum, superior vena cava draining medianly, and pulmonary veins that drained into the lower segment of the left atrium due to an anatomically enlarged single common atrium. The extracardiac findings consisted of two bilobar lungs, dysmorphic facies, low-set ears, nuchal fold edema, and small kidneys located in the iliac fossa. These findings are conclusive evidence that left atrial isomerism is a more complex syndrome. The genetic tests of the parents did not reveal any translocations of chromosomes 18 and 20 when the Fluorescent in situ Hybridization (FISH) analysis was assessed. The antenatal detection of corroboration between different structural abnormalities using serial ultrasound examinations and cardiac abnormalities, together with the detection of the affected chromosomes, improves the genetic counseling regarding the prognosis of the fetus and the recurrence rate of the condition for siblings.

A novel DNAH11 variant segregating in a sibship with heterotaxy and implications for genetic counseling.

BACKGROUND: Isomerism or heterotaxy syndrome is the loss of normal asymmetry of the internal thoraco-abdominal organs in the left-right axis and is associated with cardiovascular malformations. Mutations within DNAH11 can be associated with primary ciliary dyskinesia and heterotaxy syndromes. METHODS: We report a family of healthy, nonconsanguinous parents with subsequent pregnancies demonstrating a novel likely pathogenic variant in DNAH11 segregating in a sibship with varied presentations. RESULT: The first affected pregnancy presented with right atrial isomerism. Further DNA testing identified three variants in DNAH11 related to primary ciliary dyskinesia: a maternally inherited heterozygous variant of unknown significance (VUS) c.2772G>A (p.Met924Ile), a maternally inherited novel likely pathogenic variant c.11662C>T (p.Arg3888Cys) as well as a paternally inherited pathogenic c.1648delA variant (p.Arg550GlyfsX16). The second pregnancy inherited the same variants including the pathogenic and likely pathogenic DNAH11 variants and presented with left isomerism and extracardiac abnormalities. CONCLUSION: We present a novel likely pathogenic variant (c.11662C>T) in DNAH11 that has manifested in heterotaxy with variability in phenotypes for subsequent pregnancies of common parents. This report demonstrates that sibship illustrates potential variability in phenotypes associated with the same pathogenic variants within a family and highlights the difficulty in genetic counseling due to the variation in clinical presentation.

The Spectrum of Cardiac Anomalies Associated with Heterotaxy: A Single-Center Study of a Large Series Based on Computed Tomography.

The aim of the study was to identify and correlate the anatomical variants of cardiac structures among patients with heterotaxy. In this retrospective cross-sectional analysis of 13 years duration, 302 patients of congenital heart diseases associated with heterotaxy were studied. All these patients had undergone a meticulous clinical evaluation, echocardiography, and cardiac computed tomography. The mean age of the cohort was 38.4 months, with 180 males and 122 females. The cohort had 184 patients of right isomerism and 118 of left isomerism. More than half of the cohort had abnormal pulmonary veins. Over 75% of the cohort had low pulmonary blood flow. Abnormal relationship of great arteries was seen in nearly 69% of the cohort. Atrio-venticular canal defect was the commonest anatomical variant. Overall, 43% of the cohort had single ventricle physiology, predominantly associated with right isomerism. Heterotaxy forms a difficult anatomical subset to comprehend due to the plethora of possible abnormalities. However, unless the cardiac and visceral anatomy is delineated well, the surgical plan becomes suboptimal and often elusive, leaving tough choices for cardiac surgeon. It is essential to obtain all the possible anatomical information using additional imaging modalities to devise a basis for a comprehensive plan for medical and surgical management. A better understanding of the genetic and molecular factors in the etiology, coupled with the application of state-of-the-art imaging techniques, is likely to add to our knowledge of heterotaxy to bring about improved surgical outcomes and a better quality of life for patients suffering from this complex entity.

Isomerism of the atrial appendages: morphology and terminology.

BACKGROUND: Our aim is to identify the pathognomonic anatomical markers and the best terminology to describe the cardiac malformations associated with absent or multiple spleens, which are known as asplenia or polysplenia syndromes or isomerism. MATERIALS AND METHODS: We have reviewed 65 hearts with isomerism of atrial appendages of the Anatomical Collections of Congenital Heart Disease, Institute of Pathological Anatomy of the University of Padua consisting of 1800 specimens. All the hearts were classified according to sequential segmental classification. RESULTS: The incidence of isomerism was 3.6%. Of the total, 45 hearts with isomerism of right atrial appendages showed bilateral trilobed lungs, short bronchi, and absent spleen. The atrioventricular junction was univentricular in 49% of cases with a common atrioventricular valve in 91%. Pulmonary atresia and double outlet right ventricle were present in 40% and 47% of cases, respectively. Total anomalous pulmonary venous drainage and absent coronary sinus were always present. In 20 hearts with isomerism of left atrial appendages, bilateral bilobed lungs with long bilateral bronchi and multiple spleens were always found. The biventricular atrioventricular connection was present in 65% with a common valve in 30% of the hearts. The ventriculoarterial connection was concordant in 45% of cases, and aortic atresia and pulmonary atresia were both noted in 15% of each. An anomalous symmetric pulmonary venous drainage was observed in 65% of the hearts and interruption of inferior vena cava was found in 75% of cases. CONCLUSIONS: We believe that the appropriate terminology is based on the symmetrical morphology of the atrial appendages. The absence of the coronary sinus and the total anomalous pulmonary venous drainage are the markers of isomerism of the right atrial appendages. Symmetric pulmonary venous drainage and interruption of inferior vena cava are the markers of isomerism of left atrial appendages. In recent years, thanks to the improvement of clinical diagnosis and of surgical techniques these patients have the possibility to survive to adult age.

Loss of ciliary transition zone protein TMEM107 leads to heterotaxy in mice.

Cilia in most vertebrate left-right organizers are involved in the original break in left-right (L-R) symmetry, however, less is known about their roles in subsequent steps of the cascade - relaying the signaling and maintaining the established asymmetry. Here we describe the L-R patterning cascades in two mutants of a ciliary transition zone protein TMEM107, revealing that near-complete loss of cilia in Tmem107null leads to left pulmonary isomerism due to the failure of the midline barrier. Contrary, partially retained cilia in the node and the midline of a hypomorphic Tmem107schlei mutant appear sufficient for the formation of the midline barrier and establishment and maintenance of the L-R asymmetry. Despite misregulation of Shh signaling in both mutants, the presence of normal Lefty1 expression and midline barrier formation in Tmem107schlei mutants, suggests a requirement for cilia, but not necessarily Shh signaling for Lefty1 expression and midline barrier formation.

Persistent right umbilical vein in isomerism.

OBJECTIVE: Our objective was to evaluate the incidence of a persistent right umbilical vein in isomerism versus situs solitus. METHODS: For this retrospective, observational, nonrandomized report, we identified fetuses with confirmed right umbilical veins from all patients referred for fetal echocardiography in Southern Nevada between January 2006 and January 2019. RESULTS: For the period January 2006 to January 2019, we identified 89 fetuses with situs solitus and a right umbilical vein from 16 320 women undergoing prenatal cardiac evaluation, resulting in a right umbilical vein incidence of 0.5% in situs solitus. For the same period, we identified 36 fetuses with isomerism and confirmatory umbilical vein imaging. Of the 36, 15 (42%) had right umbilical veins. Of the 15, four of 11 (19%) had left isomerism, and 11 of 15 (73%) had right isomerism (P = .006). CONCLUSIONS: A right umbilical vein is rare with situs solitus and common with isomerism. A right umbilical vein is more common in right isomerism than left isomerism and should alert the clinician to check for isomeric situs, especially right isomerism.

Imbalanced mitochondrial function provokes heterotaxy via aberrant ciliogenesis.

About 1% of all newborns are affected by congenital heart disease (CHD). Recent findings identify aberrantly functioning cilia as a possible source for CHD. Faulty cilia also prevent the development of proper left-right asymmetry and cause heterotaxy, the incorrect placement of visceral organs. Intriguingly, signaling cascades such as mTor that influence mitochondrial biogenesis also affect ciliogenesis, and can cause heterotaxy-like phenotypes in zebrafish. Here, we identify levels of mitochondrial function as a determinant for ciliogenesis and a cause for heterotaxy. We detected reduced mitochondrial DNA content in biopsies of heterotaxy patients. Manipulation of mitochondrial function revealed a reciprocal influence on ciliogenesis and affected cilia-dependent processes in zebrafish, human fibroblasts and Tetrahymena thermophila. Exome analysis of heterotaxy patients revealed an increased burden of rare damaging variants in mitochondria-associated genes as compared to 1000 Genome controls. Knockdown of such candidate genes caused cilia elongation and ciliopathy-like phenotypes in zebrafish, which could not be rescued by RNA encoding damaging rare variants identified in heterotaxy patients. Our findings suggest that ciliogenesis is coupled to the abundance and function of mitochondria. Our data further reveal disturbed mitochondrial function as an underlying cause for heterotaxy-linked CHD and provide a mechanism for unexplained phenotypes of mitochondrial disease.

Venous Thromboembolism in Special Populations: Preexisting Cardiopulmonary Disease, Cirrhosis, End-Stage Renal Disease, and Asplenia.

Venous thromboembolism (VTE) is a common cause of morbidity and mortality. Presence of preexisting conditions, such as cardiopulmonary diseases, cirrhosis, renal dysfunction, and asplenia, commonly occurs in VTE patients. Moreover, these conditions often are risk factors for developing VTE. These preexisting conditions make VTE diagnosis and treatment challenging and worsen outcomes. Current guidelines do not include detailed features in the diagnosis and management of patients with preexisting conditions. This review discusses presence of VTE in patients with preexisting cardiopulmonary diseases, cirrhosis, renal dysfunction, and asplenia.

Sporadic isolated congenital asplenia with fulminant pneumococcal meningitis: a case report and updated literature review.

BACKGROUND: Isolated congenital asplenia (ICA) is a rare and life-threatening condition that predisposes patients to severe bacterial infections. Most of the reported cases are familial and the mode of inheritance is usually autosomal dominant. Here, we report a case of sporadic isolated asplenia and review the literature while focusing on sporadic cases. CASE PRESENTATION: We report the case of an 11-month-old female infant who developed fulminant pneumococcal meningitis. The pneumococcal vaccine-unimmunized patient was hospitalized with fever, irritability, and purpura, and was diagnosed as having meningitis, septic shock, and disseminated intravascular coagulation. Streptococcus pneumoniae was isolated from both cerebrospinal fluid and blood. She was successfully treated with prompt antibiotic therapy. During hospitalization, abdominal ultrasonography and computed tomography findings, scintigraphy results, and Howell-Jolly body-containing red blood cells indicated the presence of asplenia without any visceroarterial anomalies. Moreover, the findings of peripheral blood smears and spleen ultrasonographic examinations of her parents were normal. CONCLUSIONS: Majority of sporadic ICA cases were detected only after the onset of overwhelming infection and had a high mortality. In cases of severe invasive pneumococcal disease, a systematic search for Howell-Jolly bodies on blood smears and the presence of asplenia on abdominal imaging are essential for detecting ICA even in the absence of any family history. After the diagnosis of ICA, patient and parent education, vaccinations, antibiotic prophylaxis, and prompt empiric treatment of febrile episode should be provided.

Congenital Heart Disease Genetics Uncovers Context-Dependent Organization and Function of Nucleoporins at Cilia.

Human genomics is identifying candidate genes for congenital heart disease (CHD), but discovering the underlying mechanisms remains challenging. In a patient with CHD and heterotaxy (Htx), a disorder of left-right patterning, we previously identified a duplication in Nup188. However, a mechanism to explain how a component of the nuclear pore complex (NPC) could cause Htx/CHD was undefined. Here, we show that knockdown of Nup188 or its binding partner Nup93 leads to a loss of cilia during embryonic development while leaving NPC function largely intact. Many data, including the localization of endogenous Nup188/93 at cilia bases, support their direct role at cilia. Super-resolution imaging of Nup188 shows two barrel-like structures with dimensions and organization incompatible with an NPC-like ring, arguing against a proposed "ciliary pore complex." We suggest that the nanoscale organization and function of nucleoporins are context dependent in a way that is required for the structure of the heart.

Copy-number variant analysis of classic heterotaxy highlights the importance of body patterning pathways.

Classic heterotaxy consists of congenital heart defects with abnormally positioned thoracic and abdominal organs. We aimed to uncover novel, genomic copy-number variants (CNVs) in classic heterotaxy cases. A microarray containing 2.5 million single-nucleotide polymorphisms (SNPs) was used to genotype 69 infants (cases) with classic heterotaxy identified from California live births from 1998 to 2009. CNVs were identified using the PennCNV software. We identified 56 rare CNVs encompassing genes in the NODAL (NIPBL, TBX6), BMP (PPP4C), and WNT (FZD3) signaling pathways, not previously linked to classic heterotaxy. We also identified a CNV involving FGF12, a gene previously noted in a classic heterotaxy case. CNVs involving RBFOX1 and near MIR302F were detected in multiple cases. Our findings illustrate the importance of body patterning pathways for cardiac development and left/right axes determination. FGF12, RBFOX1, and MIR302F could be important in human heterotaxy, because they were noted in multiple cases. Further investigation into genes involved in the NODAL, BMP, and WNT body patterning pathways and into the dosage effects of FGF12, RBFOX1, and MIR302F is warranted.

ANKS3 is mutated in a family with autosomal recessive laterality defect.

Laterality defects are heterogeneous groups of congenital malformations that arise from perturbed asymmetrical development of visceral organs. The central role of the motile cilia-generated nodal flow in breaking early embryonic symmetry is reflected in the large contribution of ciliary genes to the etiology of these disorders. In a consanguineous multiplex family with a laterality defect that resembles situs inversus totalis, and complex congenital heart disease, we combined autozygome and exome analysis to identify a novel homozygous variant in ANKS3. ANKS3 encodes a recently described ciliary protein with known interaction with other ciliary proteins, and deficiency of its zebrafish ortholog causes laterality defects. Consistent with the proposed role of the ANKS3 variant in the pathogenesis of the reported family's phenotype, we show that the mutant RNA failed to rescue the laterality defect in anks3 morphants compared to wild-type RNA. Furthermore, we describe a new mutant anks3 line that also displays laterality defect in the homozygous state. Our study suggests a role for ANKS3 in right-left axis determination in humans.

Manifestations of bodily isomerism.

We report the findings present in 49 postmortem specimens from patients with so-called heterotaxy, concentrating on those found in the extracardiac systems of organs. Also known as bodily isomerism, we suggest that it is important to segregate the syndromes into their isomeric subtypes to be able to make inferences regarding likely extracardiac and intracardiac findings to allow for proper surveillance. We demonstrate that this is best done on the basis of the atrial appendages, which were isomeric in all the hearts obtained from the specimens available for our inspection. The abdominal organs do not demonstrate isomerism, and they show variable features when compared to the isomeric atrial appendages.

A rare case of heterotaxy and left ventricular non-compaction in an adult.

Heterotaxy syndrome with left ventricular non-compaction is a rare co-existence of abnormalities with unknown cause. It can be isolated with no other associations, or associated with congenital heart diseases, or it can occur with multiple other congenital abnormalities. We describe the third reported case of heterotaxy syndrome with left ventricular non-compaction presenting in an adult.