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.