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Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare inborn error of metabolism affecting fatty acid and amino acid oxidation with an incidence of 1 in 200,000 live births. MADD has three clinical phenotypes: severe neonatal-onset with or without congenital anomalies, and a milder late-onset form. Clinical diagnosis is supported by urinary organic acid and blood acylcarnitine analysis using tandem mass spectrometry in newborn screening programs. MADD is an autosomal recessive trait caused by biallelic mutations in the ETFA, ETFB, and ETFDH genes encoding the alpha and beta subunits of the electron transfer flavoprotein (ETF) and ETF-coenzyme Q oxidoreductase enzymes. Despite significant advancements in sequencing techniques, many patients remain undiagnosed, impacting their access to clinical care and genetic counseling. In this report, we achieved a definitive molecular diagnosis in a newborn by combining whole-genome sequencing (WGS) with RNA sequencing (RNA-seq). Whole-exome sequencing and next-generation gene panels fail to detect variants, possibly affecting splicing, in deep intronic regions. Here, we report a unique deep intronic mutation in intron 1 of the ETFDH gene, c.35-959A>G, in a patient with early-onset lethal MADD, resulting in pseudo-exon inclusion. The identified variant is the third mutation reported in this region, highlighting ETFDH intron 1 vulnerability. It cannot be excluded that these intronic sequence features may be more common in other genes than is currently believed. This study highlights the importance of incorporating RNA analysis into genome-wide testing to reveal the functional consequences of intronic mutations. [ABSTRACT FROM AUTHOR]

Background Postzygotic activating PIK3CA variants cause several phenotypes within the PIK3CA-related overgrowth spectrum (PROS). Variant strength, mosaicism level, specific tissue involvement and overlapping disorders are responsible for disease heterogeneity. We explored these factors in 150 novel patients and in an expanded cohort of 1007 PIK3CA-mutated patients, analysing our new data with previous literature to give a comprehensive picture. Methods We performed ultradeep targeted next-generation sequencing (NGS) on DNA from skin biopsy, buccal swab or blood using a panel including phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway genes and GNAQ, GNA11, RASA1 and TEK. Additionally, 914 patients previously reported were systematically reviewed. Results 93 of our 150 patients had PIK3CA pathogenetic variants. The merged PROS cohort showed that PIK3CA variants span thorough all gene domains, some were exclusively associated with specific PROS phenotypes: weakly activating variants were associated with central nervous system (CNS) involvement, and strongly activating variants with extra-CNS phenotypes. Among the 57 with a wild-type PIK3CA allele, 11 patients with overgrowth and vascular malformations overlapping PROS had variants in GNAQ, GNA11, RASA1 or TEK. Conclusion We confirm that (1) molecular diagnostic yield increases when multiple tissues are tested and by enriching NGS panels with genes of overlapping 'vascular' phenotypes; (2) strongly activating PIK3CA variants are found in affected tissue, rarely in blood: conversely, weakly activating mutations more common in blood; (3) weakly activating variants correlate with CNS involvement, strong variants are more common in cases without; (4) patients with vascular malformations overlapping those of PROS can harbour variants in genes other than PIK3CA. [ABSTRACT FROM AUTHOR]

mTOR dysregulation has been described in pathological conditions, such as cardiovascular and overgrowth disorders. Here we report on the first case of a patient with a complex congenital heart disease and an interstitial duplication in the short arm of chromosome 1, encompassing part of the mTOR gene. Our results suggest that an intragenic mTOR microduplication might play a role in the pathogenesis of non‐syndromic congenital heart defects (CHDs) due to an upregulation of mTOR/Rictor and consequently an increased phosphorylation of PI3K/AKT and MEK/ERK signaling pathways in patient‐derived amniocytes. This is the first report which shows a causative role of intragenic mTOR microduplication in the etiology of an isolated complex CHD. [ABSTRACT FROM AUTHOR]