Expanding MNS1 Heterotaxy Phenotype.

MNS1 (meiosis-specific nuclear structural protein-1 gene) encodes a structural protein implicated in motile ciliary function and sperm flagella assembly. To date, two different homozygous MNS1 variants have been associated with autosomal recessive visceral heterotaxy (MIM#618948). A French individual was identified with compound heterozygous variants in the MNS1 gene. A collaborative call was proposed via GeneMatcher to describe new cases with this rare syndrome, leading to the identification of another family. The first patient was a female presenting complete situs inversus and unusual symptoms, including severe myopia and dental agenesis of 10 permanent teeth. She was found to carry compound heterozygous frameshift and nonsense variants in MNS1. The second and third patients were sibling fetuses with homozygous in-frame deletion variants in MNS1 and homozygous missense variants in GLDN. Autopsies revealed a complex prenatal malformation syndrome. We add here new cases with the ultra-rare MNS1-related disorder and provide a review of all published individuals.

Variable Effects of Laterality Genes on Disharmony Between Different Thoraco-Abdominal Organs and Between Individual Cardiac Segments.

A significant percentage of patients with heterotaxy show disharmony between abdominal, bronchopulmonary and atrial situs. This finding is interesting in light of the variable effects of ciliary and laterality genes on different organs and different cardiac segments. Defects in ciliary and laterality genes that usually result in situs inversus or heterotaxy, may occasionally act separately at ventricular and/or great arteries segment, even in patients with normal viscero-atrial situs solitus. Some patients with situs solitus and transposition of great arteries or congenitally corrected transposition of great arteries have been shown to represent the result of partial segmental effects of laterality genes alterations. Specific effects of defects in laterality genes can explain disharmony between thoraco-abdominal organs and heart segments.

Asplenia in left isomerism.

Anatomical configurations where the viscero-atrial structures do not follow the usual arrangement or mirror-imaged arrangement is described conventionally as heterotaxy. Isomerism in the context of the congenitally malformed heart is a situation where some paired structures on opposite sides of the left-right axis of the body are, in morphologic terms, symmetrical mirror images of each other. It encompasses two separate entities, right and left isomerism, the former being usually associated with asplenia and the latter with polysplenia. We report herein a rare case of left isomerism that is associated with asplenia in a 4-year-old girl.

Polysplenia with situs inversus totalis, azygos continuation of the inferior vena cava, and duplication of the superior vena cava in a healthy adult: A case report.

Polysplenia syndrome is an embryological disorder whereby the usual left-right asymmetry of thoracic and abdominal viscera fails to develop. It is a rare entity, estimated to occur at a frequency of 1 in 40,000, and is often associated with cardiac and biliary abnormalities. More than 75% of patients die before the age of 5 years, and even in the absence of cardiac anomalies, only 5%-10% of patients are expected to survive into adulthood without complications. Although polysplenia syndrome encompasses a wide range of anatomic abnormalities, there is no single pathognomonic feature. Hence, the prognosis of patients with polysplenia depends on their anatomy, thus necessitating radiology in their management. Here we present a case of a 56-year-old man with polysplenia syndrome and situs inversus totalis. This presentation is atypical because polysplenia is usually considered a form of situs ambiguus, and cases with situs inversus totalis are exceedingly rare. Also noted in our patient are variations in the great vessels, including aortic arch branches and the venae cavae which are features not typically associated with either polysplenia syndrome or situs inversus totalis. The patient is healthy and asymptomatic at baseline, with his diagnosis being made incidentally. Our case report is the first to describe this unique combination of cardiothoracic and cardiovascular anatomy. It also emphasizes the importance of radiologists in caring for patients with laterality defects. As these disorders are uncommon, more data on their anatomic variations may help provide better medical care to this patient population.

Laterality, heterotaxy, and isolated congenital heart defects : The genetic basis of the segmental nature of the heart.

To date, the role of NODAL in normal and abnormal L-R asymmetry has been well established. In a recent paper, mutations of this gene have been reported in heterotaxy but also in transposition with D- or L-ventricular loop. The effects of NODAL and other laterality genes can be recognized separately in all three cardiac segments: for topology and septation of the atria, for ventricular looping, and for spiralization and alignment of the great arteries.

Outcomes of Patients Undergoing the Kawashima Procedure at an Early Age: A Single Center Experience.

BACKGROUND: Previous reports have demonstrated the safety and efficacy of performing early Kawashima procedure (KP). Despite this, more recent studies have shown that the average age at the time of operation remains greater than one year of age. We report our experience with performing KP at an earlier age than previously reported. METHODS: A retrospective review was completed of patients undergoing KP at a single center (January 2000 to June 2020). Clinical outcomes were examined. RESULTS: Initial palliation was performed in 11 out of 12 patients. Age and weight at time of KP were 8.25 months (6.4-9.7) and 7.7 kg (6.5-8.6). Intensive care unit stay was 3.16 days (1-12), overall length of stay was 9.5 days (3-22). There was one unplanned reoperation, and no mortality in the cohort. Discharge oxygen saturation was 88% (80%-98%). Seven patients developed pulmonary arteriovenous malformations (PAVMs) with six proceeding to hepatic vein incorporation (HVI). Interval time to development of PAVMs was 42.3 months (16-121). Four of the 12 patients were left with antegrade pulmonary blood flow (PBF) and three (75%) remain without PAVMs. Median follow-up was 10 years (1.5-22) with 11 of 12 (91.67%) survival for the cohort. CONCLUSIONS: The KP can be done at a younger age than previously reported with adequate early and late results. Most patients will go on to develop PAVMs and require HVI but leaving patients with some antegrade PBF is likely protective but will need further investigation to show definitive benefit.

Severe Duodenal Bleeding with Heterotaxy Syndrome Controlled by Combined Hemostatic Strategies: A Case Report.

A 73-year-old man with a history of heterotaxy syndrome and intestinal malrotation developed hemorrhagic shock due to bleeding from a duodenal ulcer. Esophagogastroduodenoscopy failed to achieve hemostasis because of restriction of the view by massive hemorrhage. Transcatheter arterial embolization cannot achieve endovascular hemostasis due to the vascular anatomy. Therefore, surgical hemostasis was achieved. Intestinal malrotation due to heterotaxy syndrome is a risk factor for gastrointestinal bleeding. Severe gastrointestinal bleeding in patients with intestinal malrotation is difficult to control with endoscopy alone. Therefore, combined therapies with endoscopy, interventional radiology, surgical procedures, and intensive care are vital for achieving a better prognosis.

A Case of Pancreatic Ductal Adenocarcinoma in an Elderly Adult With Heterotaxy Syndrome.

Heterotaxy is a syndrome characterized by a spectrum of anatomical anomalies in organ lateralization due to embryological errors. It frequently involves intrathoracic organs, especially the heart, leading to congenital abnormalities. Abdominal organs can also be affected, causing clinical features such as sepsis from asplenia or intestinal volvulus; however, these are less studied. Currently, there is no data on the relationship between heterotaxy and malignancy. We present an interesting case of an elderly adult admitted for a workup of newly diagnosed pancreatic ductal carcinoma, who was found to have heterotaxy of the stomach and spleen, with eventual tumor invasion of these organs. This case suggests that heterotaxy may increase the risk of gastrointestinal malignancy and result in a poorer prognosis due to the complexity of tumor resection involving additional organs.

Optimal timing of bridging annuloplasty and patch augmentation for heterotaxy syndrome associated with functional single ventricles.

OBJECTIVE: Although the challenging prognosis of functional single ventricles with common atrioventricular valves due to complex morphology and uncontrollable regurgitation by valvuloplasty has been highlighted, reports on when and how these extremely complicated atrioventricular valves should be repaired are few. This study investigated the timing and risk factors for valve intervention in these patients. METHODS: Between April 2006 and March 2023, 40 patients with heterotaxy syndrome associated with functional single ventricles underwent surgery. Valve intervention was performed in 14 of the 40 patients with moderate or severe atrioventricular valve regurgitation. RESULTS: The timing of the first valve intervention varied, with four, five, three, and two patients undergoing valve intervention before the cavopulmonary shunt, simultaneously with the cavopulmonary shunt, before total cavopulmonary connection, and simultaneously with total cavopulmonary connection, respectively. Mechanical valve replacements were performed in three patients. Among the 14 patients undergoing valve intervention, four died. Three of the four patients underwent valvuloplasty before the cavopulmonary shunt, including two who could undergo the cavopulmonary shunt but died after the procedure. Eight of the fourteen patients completed total cavopulmonary connection. The cumulative survival rate was not significantly different between the 14 patients who underwent and 26 who did not undergo intervention (hazard ratio, 2.52; 95% confidence interval, 0.56-11.24; P = 0.23). CONCLUSION: Our surgical strategies provide a chance for the next staged repair of common atrioventricular valves in patients with both heterotaxy and valvular regurgitation. Including patch augmentation, advanced valve intervention is possible at or after the cavopulmonary shunt.

Establishment of Cardiac Laterality.

Formation of the vertebrate heart with its complex arterial and venous connections is critically dependent on patterning of the left-right axis during early embryonic development. Abnormalities in left-right patterning can lead to a variety of complex life-threatening congenital heart defects. A highly conserved pathway responsible for left-right axis specification has been uncovered. This pathway involves initial asymmetric activation of a nodal signaling cascade at the embryonic node, followed by its propagation to the left lateral plate mesoderm and activation of left-sided expression of the Pitx2 transcription factor specifying visceral organ asymmetry. Intriguingly, recent work suggests that cardiac laterality is encoded by intrinsic cell and tissue chirality independent of Nodal signaling. Thus, Nodal signaling may be superimposed on this intrinsic chirality, providing additional instructive cues to pattern cardiac situs. The impact of intrinsic chirality and the perturbation of left-right patterning on myofiber organization and cardiac function warrants further investigation. We summarize recent insights gained from studies in animal models and also some human clinical studies in a brief overview of the complex processes regulating cardiac asymmetry and their impact on cardiac function and the pathogenesis of congenital heart defects.

Molecular Pathways and Animal Models of Defects in Situs.

Left-right patterning is among the least well understood of the three axes defining the body plan, and yet it is no less important, with left-right patterning defects causing structural birth defects with high morbidity and mortality, such as complex congenital heart disease, biliary atresia, or intestinal malrotation. The cell signaling pathways governing left-right asymmetry are highly conserved and involve multiple components of the TGF-ß superfamily of cell signaling molecules. Central to left-right patterning is the differential activation of Nodal on the left, and BMP signaling on the right. In addition, a plethora of other cell signaling pathways including Shh, FGF, and Notch also contribute to the regulation of left-right patterning. In vertebrate embryos such as the mouse, frog, or zebrafish, the specification of left-right identity requires the left-right organizer (LRO) containing cells with motile and primary cilia that mediate the left-sided propagation of Nodal signaling, followed by left-sided activation of Lefty and then Pitx2, a transcription factor that specifies visceral organ asymmetry. While this overall scheme is well conserved, there are striking species differences, including the finding that motile cilia do not play a role in left-right patterning in some vertebrates. Surprisingly, the direction of heart looping, one of the first signs of organ left-right asymmetry, was recently shown to be specified by intrinsic cell chirality, not Nodal signaling, possibly a reflection of the early origin of Nodal signaling in radially symmetric organisms. How this intrinsic chirality interacts with downstream molecular pathways regulating visceral organ asymmetry will need to be further investigated to elucidate how disturbance in left-right patterning may contribute to complex CHD.

Thoracic duct drainage patterns in heterotaxy.

BACKGROUND: Disordered lymphatic drainage is common in congenital heart diseases (CHD), but thoracic duct (TD) drainage patterns in heterotaxy have not been described in detail. This study sought to describe terminal TD sidedness in heterotaxy and its associations with other anatomic variables. METHODS: This was a retrospective, single-center study of patients with heterotaxy who underwent cardiovascular magnetic resonance imaging at a single center between July 1, 2019 and May 15, 2023. Patients with (1) asplenia (right isomerism), (2) polysplenia (left isomerism) and (3) pulmonary/abdominal situs inversus (PASI) plus CHD were included. Terminal TD sidedness was described as left-sided, right-sided, or bilateral. RESULTS: Of 115 eligible patients, the terminal TD was visualized in 56 (49 %). The terminal TD was left-sided in 25 patients, right-sided in 29, and bilateral in two. On univariate analysis, terminal TD sidedness was associated with atrial situs (p = 0.006), abdominal situs (p = 0.042), type of heterotaxy (p = 0.036), the presence of pulmonary obstruction (p = 0.041), superior vena cava sidedness (p = 0.005), and arch sidedness (p < 0.001). On multivariable analysis, only superior vena cava and aortic arch sidedness were independently associated with terminal TD sidedness. CONCLUSIONS: Terminal TD sidedness is highly variable in patients with heterotaxy. Superior vena cava and arch sidedness are independently associated with terminal TD sidedness. Type of heterotaxy was not independently associated with terminal TD sidedness. This data improves the understanding of anatomic variation in patients with heterotaxy and may be useful for planning for lymphatic interventions.

Identification and Analysis of Atrial-Bronchial-Abdominal Disharmony in Patients with Isomeric Atrial Appendages.

Ideally, the morphology of atrial appendages should solely be used to identify and differentiate patients with isomeric right and left atrial appendages. However, in clinical practice, the segregation is often indirectly based on the arrangement of thoraco-abdominal structures. The correlation between thoraco-abdominal arrangement and atrial appendages, however, is imperfect. In this study, we sought to clarify the cardiovascular malformations in patients with isomeric atrial appendages with an emphasis on atrial-thoracic-abdominal disharmony. A retrospective review of all patients who underwent cardiac CT angiography between January 2014 and June 2023 and identified to have isomeric atrial appendages was performed. Of the 366 cases (median age: 2 years [interquartile range: 11 months-7 years]), 247 (67.5%) patients had isomeric right atrial appendages while 119 (32.5%) patients had isomeric left atrial appendages. In 316 (86.3%) patients, the thoraco-abdominal arrangement was as per atrial appendage morphology while the remaining 50 (13.6%) patients had disharmonious patterns. Compared to isomeric left atrial appendages, the disharmonious pattern was more frequent with isomeric right atrial appendages (5.9% vs. 17.4%; p 0.003). Irrespective of the type of isomerism, disharmony was mostly confined to the level of the abdomen. Not all patients with isomeric atrial appendages have a harmonious thoraco-abdominal arrangement. The atrial-bronchial-abdominal disharmony is more frequent with isomeric right atrial appendages and is mostly present at the level of the abdomen. A detailed sequential segmental analysis with an independent description of each organ system is, therefore, essential for the complete evaluation of patients with isomeric atrial appendages.

Repair of infracardiac total anomalous pulmonary venous connection in a 902-gram infant with asplenia syndrome after failed umbilical venous catheter intervention.

Ductus venosus stenting via a transumbilical approach for pulmonary venous obstruction in infracardiac total anomalous pulmonary venous connection has been described. In a 902-gram infant who was diagnosed with asplenia syndrome and infracardiac total anomalous pulmonary venous connection, ductus venosus stenting was attempted by a transumbilical approach. However, ductus venosus stenting was discontinued due to bleeding from the portal vein. The bleeding subsided in time spontaneously, and total anomalous pulmonary venous connection repair with pulmonary artery banding was performed on 21 days after birth. To our knowledge, this is the first report that describes total anomalous pulmonary venous connection repair in a neonate under 1000 g body weight. Learning objective: Ductus venosus stenting is an effective palliative option, especially in the presence of high surgical risk, such as heterotaxy syndrome and a low birth weight. However, ductus venosus stenting should carefully be evaluated by assessment of anatomical configuration of umbilical vein and ductus venosus. If ductus venosus stenting is anatomically difficult, primary surgical repair may be an option even in an extremely low birth weight infant.

Heterotaxy syndrome - An unusual cause for bowel obstruction in an adult.

Heterotaxy syndrome, also known as situs ambiguous, is a spectrum of pathology due to loss of the normal right-to-left asymmetry of the thoraco-abdominal organs. This report describes the case of a 39-year-old female, previously well, who presented with bowel obstruction. CT showed features of left isomerism, with malrotation and volvulus. Contribution: Heterotaxy syndrome consists of cardiac and non-cardiac manifestations. Imaging studies play a crucial role in the individualised management of the patient.

Human Genetics of d-Transposition of Great Arteries.

Although several genes underlying occurrence of transposition of the great arteries have been found in the mouse, human genetics of the most frequent cyanotic congenital heart defect diagnosed in neonates is still largely unknown. Development of the outflow tract is a complex process which involves the major genes of cardiac development, acting on myocardial cells from the anterior second heart field, and on mesenchymal cells from endocardial cushions. These genes, coding for transcription factors, interact with each other, and their differential expression conditions the severity of the phenotype. A precise description of the anatomic phenotypes is mandatory to achieve a better comprehension of the complex mechanisms responsible for transposition of the great arteries.

Molecular Pathways and Animal Models of d-Transposition of the Great Arteries.

During normal cardiovascular development, the outflow tract becomes septated and rotates so that the separate aorta and pulmonary trunk are correctly aligned with the left and right ventricles, respectively. However, when this process goes wrong, the aorta and pulmonary trunk are incorrectly positioned, resulting in oxygenated blood being directly returned to the lungs, with deoxygenated blood being delivered to the systemic circulation. This is termed transposition of the great arteries (TGA). The precise etiology of TGA is not known, but the use of animal models has elucidated that genes involved in determination of the left- embryonic body axis play key roles. Other factors such as retinoic acid levels are also crucial. This chapter reviews the animal models presenting with TGA that have been generated by genetic manipulation or with exogenous agents.

Human Genetics of Tetralogy of Fallot and Double-Outlet Right Ventricle.

Tetralogy of Fallot (TOF) and double-outlet right ventricle (DORV) are conotruncal defects resulting from disturbances of the second heart field and the neural crest, which can occur as isolated malformations or as part of multiorgan syndromes. Their etiology is multifactorial and characterized by overlapping genetic causes. In this chapter, we present the different genetic alterations underlying the two diseases, which range from chromosomal abnormalities like aneuploidies and structural mutations to rare single nucleotide variations affecting distinct genes. For example, mutations in the cardiac transcription factors NKX2-5, GATA4, and HAND2 have been identified in isolated TOF cases, while mutations of TBX5 and 22q11 deletion, leading to haploinsufficiency of TBX1, cause Holt-Oram and DiGeorge syndrome, respectively. Moreover, genes involved in signaling pathways, laterality determination, and epigenetic mechanisms have also been found mutated in TOF and/or DORV patients. Finally, genome-wide association studies identified common single nucleotide polymorphisms associated with the risk for TOF.

Human Genetics of Defects of Situs.

Defects of situs are associated with complex sets of congenital heart defects in which the normal concordance of asymmetric thoracic and abdominal organs is disturbed. The cellular and molecular mechanisms underlying the formation of the embryonic left-right axis have been investigated extensively in the past decade. This has led to the identification of mutations in at least 33 different genes in humans with heterotaxy and situs defects. Those mutations affect a broad range of molecular components, from transcription factors, signaling molecules, and chromatin modifiers to ciliary proteins. A substantial overlap of these genes is observed with genes associated with other congenital heart diseases such as tetralogy of Fallot and double-outlet right ventricle, d-transposition of the great arteries, and atrioventricular septal defects. In this chapter, we present the broad genetic heterogeneity of situs defects including recent human genomics efforts.

Ultrasound and computed tomography angiography diagnosis of fetal right atrial isomerism with cardiac total anomalous pulmonary venous connection and intestinal malrotation: a case report and literature review.

Right atrial isomerism is a rare and severe isomerism. It is frequently associated with complex congenital heart disease and various extracardiac anomalies. Imaging diagnosis of right atrial isomerism is a challenge. Multisystem and complex anomalies in a 24-week-old fetus were diagnosed with prenatal ultrasound, postnatal computed tomography angiography (CTA), and autopsy. The ultrasound detected most major cardiovascular anomalies including right atrial isomerism and total anomalous pulmonary venous connection. The CTA further detected thoracic and abdominal malformations such as bilateral morphologically right bronchus, diaphragmatic hernia, asplenia, midline liver, and intestinal malrotation. The autopsy confirmed both ultrasound and CTA findings with additional findings, namely, bilateral trilobed lungs and bilateral morphological right auricles. Prenatal ultrasound and postnatal CTA can be complementary to each other in detecting multi-system complex anomalies. Their combined use can be useful for prenatal counseling and postpartum management.