Possible incomplete penetrance of Xq28 int22h-1/int22h-2 duplication.

Xq28 int22h-1/int22h-2 duplication is the result of non-allelic homologous recombination between int22h-1/int22h-2 repeats separated by 0.5 Mb. It is responsible for a syndromic form of intellectual disability (ID), with recurrent infections and atopic diseases. Minor defects, nonspecific facial dysmorphic features, and overweight have also been described. Half of female carriers have been reported with ID, whereas all reported evaluated born males present mild to moderate ID, suggesting complete penetrance. We collected data on 15 families from eight university hospitals. Among them, 40 patients, 21 females (one fetus), and 19 males (two fetuses), were carriers of typical or atypical Xq28 int22h-1/int22h-2 duplication. Twenty-one individuals were considered asymptomatic (16 females and 5 males), without significantly higher rate of recurrent infections, atopia, overweight, or facial dysmorphism. Approximately 67% live-born males and 23% live-born female carriers of the typical duplication did not have obvious signs of intellectual disability, suggesting previously undescribed incomplete penetrance or low expression in certain carriers. The possibility of a second-hit or modifying factors to this possible susceptibility locus is yet to be studied but a possible observational bias should be considered in assessing such challenging X-chromosome copy number gains. Additional segregation studies should help to quantify this newly described incomplete penetrance.

Prenatal exome sequencing, a powerful tool for improving the description of prenatal features associated with genetic disorders.

OBJECTIVE: Prenatal exome sequencing (pES) is now commonly used in clinical practice. It can be used to identifiy an additional diagnosis in around 30% of fetuses with structural defects and normal chromosomal microarray analysis (CMA). However, interpretation remains challenging due to the limited prenatal data for genetic disorders. METHOD: We conducted an ancillary study including fetuses with pathogenic/likely pathogenic variants identified by trio-pES from the "AnDDI-Prenatome" study. The prenatal phenotype of each patient was categorized as typical, uncommon, or unreported based on the comparison of the prenatal findings with documented findings in the literature and public phenotype-genotype databases (ClinVar, HGMD, OMIM, and Decipher). RESULTS: Prenatal phenotypes were typical for 38/56 fetuses (67.9%). For the others, genotype-phenotype associations were challenging due to uncommon prenatal features (absence of recurrent hallmark, rare, or unreported). We report the first prenatal features associated with LINS1 and PGM1 variants. In addition, a double diagnosis was identified in three fetuses. CONCLUSION: Standardizing the description of prenatal features, implementing longitudinal prenatal follow-up, and large-scale collection of prenatal features are essential steps to improving pES data interpretation.

PRKD1-related telangiectasia-ectodermal dysplasia-brachydactyly-cardiac anomaly syndrome: Case report and review of the literature.

Telangiectasia-ectodermal dysplasia-brachydactyly-cardiac anomaly (TEBC) syndrome is a rare autosomal dominant condition, recently linked to the protein kinase D1 (PRKD1) gene. The phenotype of TEBC remains incomplete at this point. Our aim is to improve the characterization of the clinical and molecular aspects of the TEBC syndrome. We report on the 8th patient carrying a heterozygous de novo variation of PRKD1 c.2134G > A, p. (Val712Met) identified by trio exome sequencing. The proband presents with partial atrioventricular septal defect, brachydactyly, ectodermal dysplasia, telangiectasia that developed in childhood, intellectual disability with microcephaly, multicystic renal dysplasia and moderate hormonal resistance. In view of this 8th description and review of the literature, it appears that neurodevelopmental disorders and microcephaly are frequently associated with PRKD1 missense variants, adding to the four main clinical signs described initially in the TEBC syndrome. Further descriptions are required to confirm the observed endocrine and kidney abnormalities. This should contribute to a more comprehensive understanding of the phenotypic spectrum and may help establish genotype-phenotype correlations. In the context of genotype-first strategy, accurate patient descriptions are fundamental. Characterization of specific syndromic associations is essential for variant interpretation support and patient follow-up, even in very rare diseases, such as the TEBC syndrome.