Although atrial septal defects (ASD) can be subdivided based on their anatomical location, an essential aspect of human genetics and genetic counseling is distinguishing between isolated and familiar cases without extracardiac features and syndromic cases with the co-occurrence of extracardiac abnormalities, such as developmental delay. Isolated or familial cases tend to show genetic alterations in genes related to important cardiac transcription factors and genes encoding for sarcomeric proteins. By contrast, the spectrum of genes with genetic alterations observed in syndromic cases is diverse. Currently, it points to different pathways and gene networks relevant to the dysregulation of cardiomyogenesis and ASD pathogenesis. Therefore, this chapter reflects the current knowledge and highlights stable associations observed in human genetics studies. It gives an overview of the different types of genetic alterations in these subtypes, including common associations based on genome-wide association studies (GWAS), and it highlights the most frequently observed syndromes associated with ASD pathogenesis.

Nuclear speckles are small, membrane-less organelles that reside within the nucleus. Nuclear speckles serve as a regulatory hub coordinating complex RNA metabolism steps including gene transcription, pre-mRNA splicing, RNA modifications, and mRNA nuclear export. Reflecting the importance of proper nuclear speckle function in regulating normal human development, an increasing number of genetic disorders have been found to result from mutations in the genes encoding nuclear speckle proteins. To denote this growing class of genetic disorders, we propose "nuclear speckleopathies". Notably, developmental disabilities are commonly seen in individuals with nuclear speckleopathies, suggesting the particular importance of nuclear speckles in ensuring normal neurocognitive development. In this review article, a general overview of nuclear speckle function, and the current knowledge of the mechanisms underlying some nuclear speckleopathies, such as ZTTK syndrome, NKAP-related syndrome, TARP syndrome, and TAR syndrome, are discussed. These nuclear speckleopathies represent valuable models to understand the basic function of nuclear speckles and how its functional defects result in human developmental disorders.

TARP (talipes equinovarus, atrial septal defect (ASD), Robin sequence, persistent left superior vena cava) syndrome is a rare X-linked disorder affecting the RBM10 gene. It was previously viewed as universally fatal in the early neonatal period, however, recent cases have shown patients surviving beyond this stage. We present a male toddler diagnosed with TARP syndrome due to a a previously unreported splicing mutation c.2295+1G>A in the RBM10 gene. At birth, he had an ASD and Robin sequence, two of the eponymous features, as well as other associated phenotypic features. During infancy, he had an extremely high alpha-fetoprotein, conjugated hyperbilirubinaemia and thrombocytopaenia, features not previously described in TARP syndrome. We discuss these findings as well as our patient's survival past the neonatal period with special consideration to recent genotype-phenotypes correlations.

TARP syndrome, characterized by talipes equinovarus, atrial septal defect, Robin sequence, and persistent left superior vena cava, is an X-linked recessive condition caused by deleterious variants in RBM10. Vitelline vascular remnants (VVR) are a rare vitelline duct anomaly with approximately 26 cases previously reported. There are no previously reported cases of VVRs in patients with TARP syndrome. We present a male neonate diagnosed with TARP syndrome via trio whole exome sequencing who had classic features of this syndrome, although his course was additionally complicated by feeding intolerance with multiple episodes of abdominal distension. Serial imaging and contrast studies of the upper GI tract and small bowel demonstrated small bowel obstruction of unclear etiology. Given the poor prognosis associated with this condition, life-sustaining measures were withdrawn, and he passed away at 38 days of age. On autopsy, a VVR was unexpectedly identified with proximal bowel dilation, explaining his feeding intolerance. We highlight the importance of full post-mortem examination in understanding the complete spectrum of manifestations of genetic syndromes and provide a review of the literature.