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.

INTRODUCTION

“Situs solitus” is defined as the normal asymmetrical arrangement of internal organs in the body. Heterotaxy syndrome is the loss of normal asymmetry of the internal thoraco‐abdominal organs in the left‐right axis and is associated with cardiac malformations (Jacobs et al., 2007). Heterotaxy syndromes can be associated with increased morbidity and mortality (Bhaskar et al., 2015). Right and left isomerism can cause complex congenital heart disease (CHD) with 5‐year survival rates ranging from 30% to 74% and 65% to 84%, respectively (Shiraishi & Ichikawa, 2012). Both survival rates are substantially lower than other forms of CHD (Shiraishi & Ichikawa, 2012). Cilia function plays a critical role in organ laterality and pathogenic variants of functional proteins in cilia results in primary ciliary dyskinesia (PCD) (Sutherland & Ware, 2009). Many genes have been reported to be associated with heterotaxy. DNAH11 (OMIM *603339) is one such gene, which codes for a dynein protein required for cilia motility. Pathogenic variants in DNAH11 have been found to cause PCD and heterotaxy (Sutherland & Ware, 2009). The inheritance pattern of DNAH11‐related Primary Ciliary Dyskinesia‐7 (OMIM #611884) is autosomal recessive, whereas the forms of inheritance for other genes that cause PCD and heterotaxy are X‐linked and autosomal dominant (Sutherland & Ware, 2009). A novel combination of a known DNAH11 (NM_001277115.1) pathogenic c.1648delA variant with a likely pathogenic DNAH11 c.11662C>T variant on the other allele in siblings presenting prenatally is described in this case report. This case reviews the phenotypic variability associated with the same gene mutations and highlights the challenges of genetic counseling. Informed consent was obtained from the patient and the hospital Research Ethics Board of Trillium Health Partners approved submission of this case for publication.

CLINICAL REPORT

A 31‐year‐old G2P1 healthy female and 36‐year‐old healthy nonconsanguineous partner, both of Polish background with no family history of congenital heart defects, presented to Clinical Genetics with increased nuchal translucency of 4.6 mm in their pregnancy. First trimester screening was positive with a one in 45 risk for trisomy 21. Noninvasive prenatal testing showed low risk for trisomies 21, 18, and 13. Amniocentesis was completed, and QF‐PCR revealed a male fetus without evidence of aneuploidy. Microarray showed a de novo 15q11.2 deletion of unknown significance (arr[GRCh37] 15q11.2(22652330_23226254)x1dn). It included TUBGCP5, NIPA1, NIPA2 and CYFIP1. Detailed ultrasound at 18 weeks showed bilateral choroid plexus cysts, small collapsed stomach, midline liver, asplenia, possible branchial cleft cysts, and was concerning for cardiac anomalies (Figure 1). Fetal echocardiogram at 20 weeks confirmed the unbalanced atrioventricular septal defect (AVSD) and hypoplastic left ventricle. In addition, right atrial isomerism, pulmonary atresia and obstructed total anomalous pulmonary venous drainage were diagnosed. Due to the initial increased nuchal translucency measurement, Noonan syndrome panel was completed and the 13 genes (BRAF, CBL, HRAS, KRAS, MAP2K1, MAP2K2, NRAS, PTPN11, RAF1, RIT1, SHOC2, SOS1, and SPRED1) tested were negative for pathogenic changes. Due to the initial question of branchial abnormalities, EYA and SIX1 sequencing were completed and there were no disease‐causing changes. Finally, due to the nature of congenital heart defects, a 15 gene congenital heart disease panel was completed. This identified a NOTCH2 (NM_024498): exon 34 c.6858C>T p.Ser2286Ser variant of unknown significance (VUS) that was inherited from one unaffected parent. This variant was inherited from one unaffected parent and reported with a total allele frequency of approximately 0.0015% (out of 66,590 chromosomes) (Lek et al., 2016). While this is a synonymous amino acid change, it could create a new donor splice site based on the Alamut software that includes splicing predictions from SpliceSiteFinder‐like, MaxEntScan, NNSPLICE, GeneSplicer and Human Splicing Finder. The family was counseled about the poor postnatal prognosis associated with hypoplastic left heart in conjunction with right atrial isomerism and obstructed pulmonary veins.

Figure 1

Still frame ultrasound images are shown diagnosing heterotaxy/right atrial isomerism. (a) A view of the fetal abdomen is shown with a midline liver and a small, collapsed stomach which is located more centrally than usual. (b) Cardiac imaging is shown with a normal size right ventricle and a hypoplastic left ventricle. The apex of the heart is towards the left. (c) The 3‐vessel view is shown which shows the great vessels in transverse imaging in the chest. The aortic arch is seen and there are bilateral superior caval veins. A main pulmonary artery and ductal arch are not seen in keeping with pulmonary atresia. A: anterior, Ao: Aortic arch, L: left, Li: Liver, LV: left ventricle, LSVC: left superior vena cava, P: Posterior, R: right, RSVC: right superior vena cava, RV: right ventricle, S: stomach

A male neonate was born at term and physical examination displayed a head circumference that measured 36 cm (at greater than the 50th percentile for 41 weeks and 1 day). There was note of periorbital fullness, mild micrognathia and overlapping second and third toes. Cardiac anomalies were confirmed. Overall findings were not typical of a single distinct common genetic syndrome. Due to the complexity of the heterotaxy, there was suspicion of an underlying etiology beyond the inherited VUS in NOTCH2 and proband only exome sequencing with mitochondrial DNA testing from the cord blood was completed. Exome sequencing identified three variants in DNAH11: c.2772G>A (M924I) variant, c.11662C>T (R3888C) variant and a pathogenic c.1648delA variant. The c.2772G>A variant has been observed in 0.0586% (18/30712) of South Asian background alleles and 40/275992 total alleles in large population cohorts, with no individuals reported in a homozygous state (Lek et al., 2016). This variant results in a conservative amino acid substitution and is likely tolerated from in‐silico analysis. Thus, it is not likely to impact secondary protein structure and is interpreted as a VUS. Neither c.11662C>T nor c.1648delA have been reported in large population database. The c.11662C>T variant causes a nonconservative amino acid substitution, is predicted to have a deleterious effect on in‐silico analysis and the same residue with a different amino acid change has been described in an affected patient with PCD and situs inversus (Knowles et al., 2012). Thus, it is interpreted as a likely pathogenic variant. The c.1648delA variant causes a frameshift with a subsequent protein truncation due to a premature stop codon at position 16 of the new reading frame (p.Arg550GlyfsX16). This variant is likely to create a loss of normal protein function and is interpreted as a pathogenic variant. Since DNAH11 is known to be associated with PCD in homozygous or compound heterozygous disease‐causing state, parental testing was performed to understand if these changes were on the same or opposite alleles. The results of the parental testing showed that the pathogenic c.1648delA DNAH11 variant was paternally inherited. The mother had the c.2772G>A variant of unknown significance and possessed the heterozygous likely pathogenic c.11662C>T change, prompting the laboratory to conclude the diagnosis of PCD being inherited in an autosomal recessive fashion with subsequent pregnancies having 25% chance risk of recurrence. The baby received compassionate care and died on the third day of life.

A year later, the couple presented with another pregnancy. Nuchal translucency at 12 weeks was increased at 8 mm. Chorionic villus sampling (CVS) testing was consequently performed, which showed normal quantitative fluorescence‐polymerase chain reaction (QF‐PCR), microarray and negative Noonan panel. Genetic testing revealed the fetus carried the same three variants in DNAH11 including c.2772G>A and c.11662C>T as seen in their previous child. At 19 weeks, fetal anatomic survey revealed a normal nuchal fold, midline liver, left‐sided stomach, dextrocardia, echogenic foci in the heart and an AVSD (Figure 2). No evidence of fetal hydrops was found, and the remainder of the fetal anatomy appeared normal.

Figure 2

Still frame ultrasound images are shown diagnosing heterotaxy/left atrial isomerism. (a) A view of the fetal abdomen is shown with a midline liver; stomach is not shown in this still image but was found to be in normal position on the left side. (b) Cardiac imaging is shown with normal size right and left ventricles. A common atrium is seen. In addition, an azygous vein is seen left and posterior to the descending aorta which is usually seen in left atrial isomerism. The apex of the heart is towards the right in keeping with dextrocardia. (c) The 3‐vessel view is shown which shows the great vessels in transverse imaging in the chest. The aortic, pulmonary artery and bilateral SVCs are seen. A: anterior, Ao: Aortic arch, Az: azygous veins, CA: common atrium, DA: descending aorta, L: left, Li: Liver, LV: left ventricle, LSVC: left superior vena cava, P: Posterior, PA: pulmonary artery, R: right, RPa: right pulmonary artery, RSVC: right superior vena cava, RV: right ventricle

At 20 weeks, a fetal echocardiogram was performed showing left atrial isomerism with dextrocardia, an AVSD variant with a common atrium, separate atrioventricular valves, an interrupted inferior vena cava with a hemiazygos continuation to the left superior vena cava and a right aortic arch. Fetal heart rate was at 110 beats per minute. The couple were counseled that the cardiac lesion was less severe and reviewed the possibility of biliary atresia, bowel malrotation, functional asplenia and potential lung and sinus problems associated with the gene mutations found. Given the congenital anomalies and gene mutations found, the couple ended the pregnancy at 22 weeks of gestation without an autopsy.

DISCUSSION

Genetic counseling is difficult when there is heterogeneity in clinical presentation as highlighted by this case which presents two affected pregnancies with the same novel likely pathogenic c.11662C>T (p.Arg3888Cys) DNAH11 variant segregating with a known pathogenic variant in the other allele. The pathogenic potential of this variant can be described in the manifestation of isomerism and CHD. To date, no literature has described the phenotype of the c.11662C>T likely pathogenic variant (Table 1). Previous studies have shown gene mutations causing primary ciliary dyskinesia (Table 1) associated with situs solitus (reference from table), situs inversus (reference from table) and heterotaxy (reference from table). Our cases are the first reported with in utero presentation of heterotaxy syndromes with gene mutations linked to primary ciliary dyskinesia. Both pregnancies were affected by the same two variants in DNAH11 but presented with different forms of isomerism and significant variability in the complexity of the associated cardiac malformations, illustrating the variability in phenotypes associated with the same pathogenic variants within a family. One neonate had significant cardiac anomalies with high probability of poor outcome, while the second pregnancy was affected with milder cardiac anomalies. However, there was potential for an increase in severe extracardiac anomalies such as biliary atresia in the second pregnancy. In both pregnancies, there was the possibility of phenotypic presentation of PCD with variable severity. DNAH11 variants were found previously to be associated with CHD and heterotaxy syndrome (Liu et al., 2019) and it is known that there is a substantial genetic component to isomerism (Bamford et al., 2000; Kaasinen et al., 2010; Kosaki, Kosaki, et al., 1999; Kosaki, Gebbia, et al., 1999; Mohapatra et al., 2008; Zhu et al., 2007). In addition, microdeletions in 15q11.2 have also been observed to be significantly associated with CHD (Vanlerberghe et al., 2015). This report of a novel gene mutation linked to both PCD and heterotaxy syndromes highlights the importance of discussing this association during prenatal counseling as PCD may increase risk of poor outcome in individuals with heterotaxy syndrome.

Table 1

Literature review of patients with DNAH11 variants associated with primary ciliary dyskinesia‐7 (CILD7)

Patient identifier from reference	Genotype	Age at test/diagnosis	Cardiac features	Extra‐cardiac features	Reference
Patient 1	Compound Heterozygote: Heterozygous DNAH11 c.2772G>A; p.Met924Ile Heterozygous DNAH11 c.11662C>T; p.Arg3888Cys Heterozygous DNAH11 c.1648delA; p.Arg550Glyfs*16	18 weeks (prenatal)	At 20 weeks: Unbalanced atrioventricular septal defect Hypoplastic left ventricle Right atrial isomerism Pulmonary atresia Obstructed total anomalous pulmonary venous drainage	At 18 weeks Bilateral choroid plexus cysts Small collapsed stomach Midline liver Asplenia Possible branchial cleft cysts At 41 weeks: (postnatal) Primary ciliary dyskinesia	Current study
Patient 2	Compound Heterozygote: Heterozygous DNAH11 c.11662C>T; p.Arg3888Cys Heterozygous DNAH11 c.1648delA; p.Arg550Glyfs*16 Heterozygous DNAH11 c.1648delA; p.Arg550Glyfs*16	19 weeks (prenatal)	At 19 weeks Echogenic foci Dextrocardia At 20 weeks Atrioventricular septal defect Dextrocardia Left atrial isomerism Atrioventricular septal defect variant with a common atrium 110 bpm fetal heart rate Separate atrioventricular valves Interrupted inferior vena cava with a hemiazygos continuation to the left superior vena cava and a right aortic arch	At 19 weeks Primary ciliary dyskinesia Normal nuchal fold Midline liver Left‐sided stomach At 20 weeks Polysplenia Bowel malrotation	Current study
Patient C.C	Homozygous DNAH11 c.8554C>T; p.Arg2852* (603339.0001)	10 days old	At 10 days Situs inversus Dextrocardia	At 10 days Visceral situs inversus with structurally normal spleen Respiratory distress At 6 months Cystic fibrosis Primary ciliary dyskinesia with abnormal ciliary motion	Pan et al. (1998), Bartoloni et al. (2002)
Patient II‐2	Compound Heterozygotes: Heterozygous DNAH11 c.12384C>G; p.Tyr4128* (603339.0002) and heterozygous DNAH11 c.13552_13608del; 57‐BP DEL, NT13552 (603339.0003)	27 years old	Situs inversus Dextrocardia	Primary ciliary dyskinesia with inflexible ciliary beating pattern and normal axonemal ultrastructure Chronic respiratory infections (sinusitis, bronchitis)	Schwabe et al. (2008)
Patient II‐3		25 years old	Situs solitus	Primary ciliary dyskinesia with inflexible ciliary beating pattern and normal axonemal ultrastructure Chronic respiratory infections (sinusitis, bronchitis, pneumonia)
Patient II‐4		24 years old	Situs solitus	Primary ciliary dyskinesia with inflexible ciliary beating pattern and normal axonemal ultrastructure Chronic respiratory infections (sinusitis, bronchitis, pneumonia) Bronchiectasis
Patient II‐6		20 years old	Situs solitus	Chronic respiratory infections (sinusitis, bronchitis, pneumonia) Bronchiectasis
Patient II‐9		16 years old	Situs solitus	Primary ciliary dyskinesia with inflexible ciliary beating pattern and normal axonemal ultrastructure Chronic respiratory infections (sinusitis, bronchitis, pneumonia)
Patient II‐11		12 years old	Situs solitus	Primary ciliary dyskinesia with inflexible ciliary beating pattern and normal axonemal ultrastructure Chronic respiratory infections (sinusitis, bronchitis, pneumonia) Bronchiectasis
Patient #730	Compound Heterozygote: Heterozygous DNAH11 c.8719C>T; p.Arg2907* (603,339.0004) and heterozygous DNAH11 c.7793C>T; p.Pro2598Leu (603339.0005)	4 years old	Situs solitus	Primary ciliary dyskinesia with rapid, erratic dyskinetic ciliary beating but normal ciliary ultrastructure Neonatal respiratory symptoms Chronic cough Rhinitis Otitis	Lucas et al. (2012)
Patient 1	Compound Heterozygote: Heterozygous DNAH11 c.2406G>A; p.Trp802* and heterozygous DNAH11 c.846G>C; p.Met282Ile	3.8 years old	Isolated right heart Complete atrioventricular canal Double outlet right ventricle Atrial septal defect	Heterotaxy Abnormal ciliary function: immotile, discordant, and restricted	Liu et al. (2019)
Patient 2	Compound Heterozygote: Heterozygous DNAH11 c.10379C>A; p.Thr3460Lys and heterozygous DNAH11 c.13273G>A; p.Gly4425Ser	4.4 years old	Congenital heart disease	Heterotaxy Abnormal ciliary movement: discordant and restricted
Patient 3	Compound Heterozygote: Heterozygous DNAH11 c.1339G>A; p.Gly447Arg and heterozygous DNAH11 c.3470T>G; p.Leu1157Arg	5.4 years old	Congenital heart disease	Heterotaxy Abnormal ciliary movement: immotile and restricted
Patient 4	Compound Heterozygote: Heterozygous DNAH11 c.6785T>C; p.Ile2262Thr and heterozygous DNAH11 c.11398G>C; p.Asp3800His	3.6 years old	Congenital heart disease	Heterotaxy Ciliary dysfunction: discordant and restricted
Patient 5	Compound Heterozygote: Heterozygous DNAH11 c.8275T>C; p.Phe2759Leu and heterozygous DNAH11 c.13183C>T; p.Arg4395* and heterozygous DNAH11 c.5470dupC; p.Ser1823fs	0.5 years old	Congenital heart disease	Heterotaxy Ciliary dysfunction: immotile and restricted
Patient 6	Compound Heterozygote: Heterozygous DNAH11 c.10829A>T; p.Asp3610Val and heterozygous DNAH11 c.727A>G; p.Ile243Val	8.6 years old	Isolated right heart Pulmonary atresia Levo‐transposition of the great arteries Atrial septal defect	Heterotaxy Abnormal ciliary function: immotile and restricted
Patient 11057	Homozygous DNAH11 c.13183C>T; p.Arg4395Ter	3 years old	Situs inversus	Probable primary ciliary dyskinesia: immotile cilia, complete absence of outer dynein arms Neonatal respiratory distress syndrome Rhinitis Sinusitis Otitis Bronchitis without wheezing	Boaretto et al. (2016)
Patient 11174	Compound Heterozygote: Heterozygous DNAH11 c.2753G>T; p.Gly918Val and heterozygous DNAH11 c.12796_12801delinsATA; p.Phe4266_Asn4267delinsIle	10 years old		Probable primary ciliary dyskinesia: normal ciliary ultrastructure, immotile and stiff cilia Rhinitis Sinusitis Otitis Bronchitis with wheezing Cough Asthma
Patient 11228	Compound Heterozygote: Heterozygous DNAH11 c.9304G>A; p.Gly3102Ser and heterozygous DNAH11 c.4922C>G; p.Ser1641*	1 year old	Situs inversus	Probable primary ciliary dyskinesia: normal ciliary ultrastructure with atypical beating pattern Rhinitis Bronchitis without wheezing Cough
Patients A	Compound heterozygote: Heterozygous DNAH11 c.883‐1G>A and heterozygous DNAH11 c.4145G>A; p.Trp1382*	15 years and 5 months old	Situs inversus	Primary ciliary dyskinesia: swollen and compound cilia, abnormal nonflexible ciliary beating pattern with reduced cilium bending capacity, hyperkinetic beat of cilia, and immotile cilia Chronic respiratory symptoms Neonatal purulent rhinitis with frequent relapses Chronic rhinosinusitis Otitis Bronchiectasis Bronchiectasis and atelectasis of the left middle lobe associated with fibrotic areas and pan‐sinusitis	Pifferi et al. (2010)
Patient B	Compound heterozygote: Heterozygous DNAH11 c.883‐1G>A and heterozygous DNAH11 c.4145G>A; p.Trp1382*	9 years and 4 months old	Situs inversus	Primary ciliary dyskinesia: swollen and compound cilia, abnormal nonflexible ciliary beating pattern with reduced cilium bending capacity, hyperkinetic beat of cilia, and immotile cilia Chronic respiratory symptoms Recurrent wheezy bronchitis Pneumonia Pan‐sinusitis and bronchioloectasis of the left middle lobe associated with fibrotic areas
Patient C	Compound heterozygote: Heterozygous DNAH11 c.8135A>G; p.His2712Arg and heterozygous DNAH11 c.10284G>A; p.Gly3429Arg	8 years old	Situs inversus Partial interatrial defect	Primary ciliary dyskinesia: swollen and compound cilia, abnormal nonflexible ciliary beating pattern with reduced cilium bending capacity, hyperkinetic beat of cilia, and immotile cilia Neonatal respiratory distress Recurrent otitis Pneumonia Fibrotic area in the left middle lobe, maxillary and sphenoid sinusitis with agenesis of frontal sinuses
PCD623	Homozygous DNAH11 c.4438C>T; p. Arg1480*	24 years old	Situs solitus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis	Knowles et al. (2012)
PCD1022	Homozygous DNAH11 c.4333C>T; Arg1445*	4 years old	Situs solitus	Primary ciliary dyskinesia: normal ultrastructure Neonatal respiratory distress syndrome Otitis Sinusitis
OP20‐II:1	Homozygous DNAH11 c.11663G>A; Arg3888His	12 years old	Situs inversus	Primary ciliary dyskinesia Otitis Bronchiectasis
PCD108	Compound heterozygote: Heterozygous DNAH11 c.4516_4517delCT; p.Leu1506Serfs*10 and heterozygous DNAH11 c.7266+1G>A; p.Thr2379_Gln2422del	24 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic cilia Neonatal respiratory distress syndrome Otitis Sinusitis
PCD157	Compound heterozygote: Heterozygous DNAH11 c.6244C>T; p.Arg2082* and heterozygous DNAH11 c.11929G>T; p.Glu3977*	12 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis
PCD761	Compound heterozygote: Heterozygous DNAH11 c.2275‐1G>C; p.Tyr759_Glu889del and heterozygous DNAH11 c.13213dC; p.Arg4405Alafs*1	30 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis
PCD919	Compound heterozygote: Heterozygous DNAH11 c.13065_67delCCT; p.4356delLeu and heterozygous DNAH11 c.13075C>T; p.Arg4359*	8 years old	Situs ambiguous	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis
OP98‐II:1	Compound heterozygote: Heterozygous DNAH11 c.7914G>C; p.Trp2604* and heterozygous DNAH11 c.13333_34insACCA; p.Ile4445Asnfs*3	20 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Otitis Bronchiectasis Sinusitis
PCD565	Compound heterozygote: Heterozygous DNAH11 c.5778+1G>A; p.Val1821Thrfs*7 and heterozygous DNAH11 c.13061T>A; p.Leu4354His	7 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis
PCD1077	Compound heterozygote: Heterozygous DNAH11 c.3901G>T; p.Glu1301* and heterozygous DNAH11 c.11804C>T; p.Pro3935Leu	2 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure Neonatal respiratory distress syndrome Otitis Sinusitis
PCD1126	Compound heterozygote: Heterozygous DNAH11 c.12064G>C; p.Ala4022Pro and heterozygous DNAH11 c.13504_05insGAAGA; p.Thr4502Argfs*14	42 years old	Situs solitus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Bronchiectasis Sinusitis
OP235‐II:2	Compound heterozygote: Heterozygous DNAH11 c.12697C>T; p.Gln4233* and heterozygous DNAH11 c.12980T>C; p.Leu4327Ser	21 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Bronchiectasis Sinusitis
OP41‐II:1	Compound heterozygote: Heterozygous DNAH11 c.350A>T; p.Glu117Val and heterozygous DNAH11 c.7148T>C; p.Leu2383Pro	13 years old	Situs inversus	Primary ciliary dyskinesia: normal ultrastructure, dyskinetic and hyperkinetic beating pattern Neonatal respiratory distress syndrome Otitis Sinusitis
PCD812	Compound heterozygote: Heterozygous DNAH11 c.5815G>A; p.Gly1939Arg and heterozygous DNAH11 c.13373C>T; p.Pro4458Leu	8 years old	Situs inversus	Primary ciliary dyskinesia Neonatal respiratory distress syndrome Otitis Sinusitis

Prenatal genetic counseling must consider the phenotypic variations associated with gene mutations when reviewing possible outcomes with families. Specifically, isomerism demonstrates phenotypic variation, as in our case presentation, that may induce a greater negative emotional impact in the caregivers due to uncertainty. This necessitates genetic counseling that factors the psychological social and financial when reviewing a genetic diagnosis (Werner, Latal, Valsangiacomo Buechel, Beck, & Landolt, 2014). Werner et al. (2014) showed that the presence of a genetic disorder in a child with CHD significantly increased the perceived impact on the family (Werner et al., 2014). Parents of children with CHD report a lower quality of life than parents of healthy children (Lawoko & Soares, 2003). This reduction in the quality of life has been determined by factors such as care‐giving time, sick‐leave, financial difficulties, psychological problems (distress and hopelessness), and social isolation (Lawoko & Soares, 2002, 2003). The stress that a family endures when a child is born with a genetic disorder can be better managed through appropriate prenatal genetic counseling and expectation setting.

Prenatal detection rates of isomerism syndrome have improved drastically, and most cardiovascular anomalies can be defined with substantial accuracy by experienced fetal echocardiographers (Lim et al., 2005). It is crucial to identify extracardiac findings during prenatal screening as these extracardiac anomalies have been found to contribute significantly to morbidity and mortality (Gottschalk et al., 2016). Although the major contributing causes to mortality in fetuses with isomerism are cardiovascular malformations, extracardiac anomalies also have a significant impact on the outcome of newborns (Gottschalk et al., 2016). In conjunction with complex cardiac defects and heterotaxy, both siblings presented with extracardiac anomalies. The first affected pregnancy presented with asplenia, a small midline stomach with a central liver, while the second child was stillborn and presented with polysplenia and bowel malrotation. Another important and common extracardiac anomaly in heterotaxy syndrome patients is biliary atresia, which has been found to be the most important extracardiac contributor to postnatal outcome with a high mortality and morbidity (Gottschalk et al., 2016). Intestinal malformation, which has been seen in 70% of heterotaxy syndrome cases, was also suspected to cause midgut volvulus with potentially catastrophic consequences (Gottschalk et al., 2016).

Some challenges exist with prenatal screening including the failed detection of extracardiac anomalies such as bowel obstruction, biliary atresia, immune dysfunction and anomalous pulmonary venous return, despite thorough inspection (Lim et al., 2005) (Gottschalk et al., 2016). Prenatal diagnosis of biliary atresia is also very difficult because the morphology of the gallbladder is highly variable, and the usefulness of enzyme analysis in the amniotic fluid is not clear (Gottschalk et al., 2016). Finally, prenatal diagnosis of left isomerism has been reported to exist with a morphologically normal heart (De Paola et al., 2009), further strengthening the value of extracardiac findings. Genetic counseling in families with heterotaxy should emphasize the degree of uncertainty that exists with postnatal presentation. The summary and strengths of the cases presented are: 1) the significant association between isomerism and underlying genetics with the novel likely pathogenic c.11662C>T variant in DNAH11 associated with disease, and 2) the importance of prenatal screening and genetic counseling once an abnormality indicating isomerism is detected during screening in order to ensure timely identification of genetic disease, as well as to allow for informative genetic counseling to aid in management decisions for the family.

CONFLICT OF INTEREST

All authors declare that that there is no conflict of interest in connection with the work submitted.

AUTHOR CONTRIBUTION

VT, EG, and AN designed the work. VT provided the Figures 1 and 2. VT and EG provided the clinical information of the patient. AN compiled the summary of clinical information of the cases. AN and AE performed detailed literature review and developed the literature summary on Table 1. All authors offered a major contribution in the writing of the manuscript. VT and EG provided critical feedback on the manuscript. All authors approved the final version.