BackgroundMicrodeletions at 17q11.2 often encompass NF1 gene, is the cause for NF1 microdeletion syndrome. Microdeletion at 17q11.2 without the involvement of NF1 gene is rarely reported.Case presentationHere we reported a patient carrying a novel de novo deletion at 17q11.2 adjacent to NF1 gene, who presented with developmental delay, short stature, postnatal microcephaly, underweight and dysmorphic features including flat facial profile, dolicocephaly, hypertelorism, short philtrum, flat nasal bridge and posteriorly rotated and low set ears. Chromosomal microarray analysis revealed a 1.69 Mb de novo deletion at 17q11.2 adjacent to NF1 gene, which involves 43 RefSeq genes. We compared this with four overlapping deletions at this interval.ConclusionsA rare de novo microdeletion at 17q11.2 not involving NF1 gene is associated with developmental delay and dysmorphic features. Seven genes, TAOK1, PHF12, NUFIP2, SLC26A4, SEZ6, GIT1 and TRAF4 are possible candidates for the clinical features of our patient. The delineation of this rare deletion and description of associated clinical phenotypes will help to understand the genotype-phenotype correlation of genomic imbalances at this locus.
Hydrocephalus due to aqueductal stenosis (HSAS; Online Mendelian Inheritance in Man #307000) is a rare X-linked, recessively-inherited disease characterized by severe hydrocephaly and occasionally adducted thumbs, in addition to intellectual disability and spasticity in surviving individuals. The present study described two fetuses with severely enlarged ventricles of the brain. The clinical diagnosis of HSAS was made on the basis of family history and sonographic findings. Molecular testing of the L1 cell adhesion molecule (L1CAM) gene revealed two novel hemizygous L1CAM variants, c.998C>T(p.Pro333Leu) and c.2362G>T(p.Val788Phe). The variants affect the highly conserved amino acids which are located in the key domains of the protein (the fourth Ig domain and second FnIII domain, respectively). The two variants were predicted to be 'disease causing' by a number of prediction tools, and have been classified as likely pathogenic following the American College of Medical Genetics and Genomics/Association for Molecular Pathology guidelines. The present study highlights the importance of combining family history, prenatal ultrasonography and molecular testing in the diagnosis of HSAS. The novel variants expand the mutational spectrum of L1CAM gene in the Chinese population, and could be used in genetic counseling, carrier testing of female relatives, and prenatal, as well as preimplantation genetic diagnosis.
congenital generalized lipodystrophy (cGl) is a clinically and genetically heterogeneous condition with autosomal recessive inheritance. CGL is classified into four subtypes on the basis of causative genes. This study reported on a 2-month-old male infant diagnosed with CGL with generalized lipoatrophy and skin hyperpigmentation. Whole exome sequencing (WES) identified a heterozygous small insertion (c.545_546insccG) in Berardinelli-Seip congenital lipodystrophy 2 (BSCL2) that was inherited from the infant's mother. copy number variation analysis using exome data suggested a heterozygous deletion involving exon 3 that was inherited from the infant's father. This finding was confirmed by multiplex ligation-dependent probe amplification test. Gap-PCR revealed breakpoints and confirmed a 1274 bp heterozygous deletion encompassing exon 3 of BSCL2 (c.213-1081_c.294+111). This deletion is different from the founder 3.3 kb deletion involving exon 3 of BSCL2 in the Peruvian population. an 11-bp microhomology at the breakpoints may mediate the deletion, and its presence indicates the independent origins of the exon 3 deletion between chinese and Peruvian populations. The present results expanded the mutational spectrum of the BSCL2 gene in the chinese population and suggested that introns 2 and 3 of BSCL2 are prone to recombination. Thus, exon 3 deletion should be considered for patients with CGL2 when only one BSCL2 variant is detected through WeS.
Objective: To evaluate the efficacy of Cell-free DNA (cfDNA) based non-invasive prenatal testing (NIPS) in detecting fetal chromosomal aneuploidies among twin pregnancies. Materials and Methods: A cohort of 384 women with twin pregnancies were recruited for chromosomal aneuploidies testing through NIPS. cfDNA was extracted from maternal blood serum and sequenced by massively parallel sequencing (MPS). Result: Two cases of trisomy 21 (T21), one case of trisomy 13 (T13), and two cases of sex chromosomal aneuploidies (SCA) in twin pregnancies were correctly identified through MPS and confirmed their discordant fetal karyotypes (one normal and the other trisomy) by karyotyping; 378 twin pregnancies cases with negative NIPS results were confirmed through postnatal phone follow-up. NIPS detection rate and positive predictive value for T21, T13, and SCA were 100%, respectively, in twin pregnancies; sensitivity and specificity towards T21 and T13 in twin pregnancies were both 100%. Conclusion: cfDNA based NIPS for fetal chromosomal aneuploidy have shown a satisfactory clinical performance in twin pregnancies.
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