A 33-years-old gravida 3 para 1 pregnant woman who diagnosed with fetal anomaly in their local hospital were referred to our hospital at 24+2 weeks gestation. The woman was healthy and did not take any medication during her pregnancy.
A second trimester ultrasound and echocardiography showed several malformations: EA (the displacement of the septal tricuspid leaflet from the mitral valve annulus was 0.58 cm) with severe tricuspid regurgitation, heart dilatation, perimembranous VSD (Figure 1). The Fractional shortening (FS) was reduced to 11.3%. Mild seroperitoneum, SUA, Slight pericardial effusion were observed. After detailed counseling, the couple decided to terminate the pregnancy with genetic tests and have an autopsy.
On pathologic examination, the gross pathological appearance is the myocardial wall of the left ventricle is thick and loose, elongated anterior tricuspid leaflet, and mild displacement of posterior and septal tricuspid. Histologically, there is focal necrosis of the heart muscle and pathological pigmentation.
When the genetic abnormal MYH7 was identified in the fetal, the at-risk first degree relatives of the pregnant were recommended to undergo screening. Her daughter has normal growth and development, since she is clinically asymptomatic who had never got any cardiac evaluation ever before. The mother of the pregnant and family members had no symptoms to arrhythmias and major events such as heart failure, thromboembolism, and sudden cardiac death.
Transthoracic echocardiography was taken to assess the left ventricular size, thickness, and systolic and diastolic function, and look for any associated congenital heart defects. Echocardiography performed on the pregnant indicated normal cardiac anatomy (Video 1), but we found the old daughter (III-1) and mother (II-1) of the pregnant were LVNC which characterised by preserved cardiac function and left ventricular prominent trabeculations and sinusoids communicating with its cavity on apical four-chamber view, especially in their apex. It was also show normal left ventricular size and with preserved systolic and diastolic function. The end-systolic ratio of noncompacted to compacted (NC/C) myocardium was >2.0 at the end of diastole, which meeting the Jenni echocardiography criteria  (Figure 2). Both of them also noted mild mitral and tricuspid regurgitation. There were no intracardiac thrombi and the right ventricle (RV) had normal size and systolic function. The electrocardiogram of the grandmother was abnormal which showed a T-wave inversion. Considering the LVNC is isolated and asymptomatic, the 7 years girl and her grandmather don’t obtained the cardiovascular magnetic resonance imaging (CMR).
A trio (fetus and the parents) whole-exome sequencing was performed as described previously . Briefly, genomic DNA was extracted, hybridized and enriched for whole-exome sequencing. The captured libraries were sequenced using Illumina NovaSeq 6000 (Illumina, Inc., San Diego, CA, USA). Then, the sequencing data were aligned to the human reference genome (hg19/GRCh37) using BWA (http://bio-bwa.sourceforge.net/) and PCR duplicates were removed by using Picard v1.57 (http://picard.sourceforge.net/). GATK https://software.broadinstitute.org/gatk/) was employed for variant calling. ANNOVAR (http://wannovar.wglab.org/) was used for variant annotation and interpretation. Variants were filtered out if their minor allele frequency among East Asians in the GnomAD database: ≥ 0.1% for variants associated with autosomal dominant disorders and ≥ 1% for variants associated with autosomal recessive disorders, respectively. We then evaluated each variant considering a careful review of the literature and in silico prediction tools (SIFT, Polyphen2, and Mutation Taster for missense variants and MaxEntScan, GeneSplicer and Human Splicing Finder for splicing variants). For known CHD or cardiomyopathy genes, pathogenicity of variants was determined according to the American College of Medical Genetics and Genomics guidelines that recommend classifying variants into five categories: pathogenic, likely pathogenic, uncertain significance, likely benign, or benign.
As a result, Whole-exome sequencing identified a maternal inherited heterozygous splice site mutation in MYH7 (NM_000257.3:c.732+1G>A). The mutation has been reported previously in several individuals with LVNC and one individual with isolated EA [7-10]. In contrast, it is present in only one individual (allele frequency: 3.98e-6) in the gnomAD database (https://gnomad.broadinstitute.org). This variant is reported as Pathogenic in ClinVar. This variant showed a deleterious effect by multiple in silico algorithms. In summary, the variant is classified as likely pathogenic according to the American College of Medical Genetics and Genomics guidelines . Subsequent Sanger sequencing confirmed that the mutation was heterozygous in the fetus, the grandmother, the mother and the old sister (Figure 3). In the family, the MYH7 mutation segregated with cardiac abnormality and was observed in 3/3 affected individuals, where a blood sample was available, and in one apparently healthy individual. To further assess the effect of this variant at the mRNA level, we attempted to perform the qPCR experiment using RNA from blood lymphocytes (other tissue was not available) but were unable to amplify any product (data not shown).