High positive predictive value of CNVs detected by clinical exome sequencing in suspected genetic diseases.

BACKGROUND: Genetic disorders often manifest as abnormal fetal or childhood development. Copy number variations (CNVs) represent a significant genetic mechanism underlying such disorders. Despite their importance, the effectiveness of clinical exome sequencing (CES) in detecting CNVs, particularly small ones, remains incompletely understood. We aimed to evaluate the detection of both large and small CNVs using CES in a substantial clinical cohort, including parent-offspring trios and proband only analysis. METHODS: We conducted a retrospective analysis of CES data from 2428 families, collected from 2018 to 2021. Detected CNV were categorized as large or small, and various validation techniques including chromosome microarray (CMA), Multiplex ligation-dependent probe amplification assay (MLPA), and/or PCR-based methods, were employed for cross-validation. RESULTS: Our CNV discovery pipeline identified 171 CNV events in 154 cases, resulting in an overall detection rate of 6.3%. Validation was performed on 113 CNVs from 103 cases to assess CES reliability. The overall concordance rate between CES and other validation methods was 88.49% (100/113). Specifically, CES demonstrated complete consistency in detecting large CNV. However, for small CNVs, consistency rates were 81.08% (30/37) for deletions and 73.91% (17/23) for duplications. CONCLUSION: CES demonstrated high sensitivity and reliability in CNV detection. It emerges as an economical and dependable option for the clinical CNV detection in cases of developmental abnormalities, especially fetal structural abnormalities.

Characterization of a wheat stable QTL for spike length and its genetic effects on yield-related traits.

Spike length (SL) is one of the most important agronomic traits affecting yield potential and stability in wheat. In this study, a major stable quantitative trait locus (QTL) for SL, i.e., qSl-2B, was detected in multiple environments in a recombinant inbred line (RIL) mapping population, KJ-RILs, derived from a cross between Kenong 9204 (KN9204) and Jing 411 (J411). The qSl-2B QTL was mapped to the 60.06-73.06 Mb region on chromosome 2B and could be identified in multiple mapping populations. An InDel molecular marker in the target region was developed based on a sequence analysis of the two parents. To further clarify the breeding use potential of qSl-2B, we analyzed its genetic effects and breeding selection effect using both the KJ-RIL population and a natural mapping population, which consisted of 316 breeding varieties/advanced lines. The results showed that the qSl-2B alleles from KN9204 showed inconsistent genetic effects on SL in the two mapping populations. Moreover, in the KJ-RILs population, the additive effects analysis of qSl-2B showed that additive effect was higher when both qSl-2D and qSl-5A harbor negative alleles under LN and HN. In China, a moderate selection utilization rate for qSl-2B was found in the Huanghuai winter wheat area and the selective utilization rate for qSl-2B continues to increase. The above findings provided a foundation for the genetic improvement of wheat SL in the future via molecular breeding strategies.

When NIPT meets WES, prenatal diagnosticians face the dilemma: genetic etiological analysis of 2,328 cases of NT thickening and follow-up of pregnancy outcomes.

Objective: To assess the performance of diverse prenatal diagnostic approaches for nuchal translucency (NT) thickening and to investigate the optimal prenatal screening or diagnostic action with a NT thickening of 95th percentile-3.50 mm. Methods: A retrospective analysis of 2,328 pregnancies with NT ≥ 95th percentile through ultrasound-guided transabdominal chorionic villus sampling (CVS), amniocentesis, or cordocentesis obtained clinical samples (chorionic villi, amniotic fluid, and cord blood), and real-time quantitative fluorescent PCR (QF-PCR), chromosome karyotyping (CS), chromosome microarray analysis (CMA), or whole exome sequencing (WES) were provided to identify genetic etiologies. Results: In this study, the incidence of chromosomal defects increased with NT thickness. When NT ≥ 6.5 mm, 71.43% were attributed to genetic abnormalities. The 994 gravidas with fetal NT thickening underwent short tandem repeat (STR), CS, and CMA. In 804 fetuses with normal karyotypes, CMA detected 16 (1.99%) extra pathogenic or likely pathogenic copy number variations (CNVs). The incremental yield of CMA was only 1.16% (3/229) and 3.37% (10/297) in the group with NT 95th percentile-2.99 mm and NT 3.0-3.49 mm, separately. Among the 525 gravidas with fetal NT thickening who underwent STR, CMA, and WES, the incremental yield of WES was 4.09% (21/513). In the group of NT 95th percentile-2.99 mm, there were no additional single-nucleotide variations (SNVs) detected in WES, while in 143 cases with NT of 3.0-3.49 mm, the incremental yield of WES was 5.59% (8/143). Conclusion: In the group of NT 95th percentile-3.0 mm, since chromosomal aneuploidy and chromosomal copy number variation were the primary causes and the additional contribution of CMA and WES was not significant, we recommend NIPT-Plus for pregnant women with a NT thickening of 95th percentile-3.0 mm first. In addition, comprehensive prenatal genetic testing involving CMA and WES can benefit pregnancies with NT thickening of 3.0-3.49 mm.

Clinical utility of chromosomal microarray analysis and whole exome sequencing in foetuses with oligohydramnios.

OBJECTIVES: To evaluate the clinical utility of chromosomal microarray analysis (CMA) and whole exome sequencing (WES) in foetuses with oligohydramnios. METHODS: In this retrospective study, 126 fetuses with oligohydramnios at our centre from 2018 to 2021 were reviewed. The results of CMA and WES were analysed. RESULTS: One hundred and twenty-four cases underwent CMA and 32 cases underwent WES. The detection rate of pathogenic/likely pathogenic (P/LP) copy number variant (CNV) by CMA was 1.6% (2/124). WES revealed P/LP variants in 21.8% (7/32) of the foetuses. Six (85.7%, 6/7) foetuses showed an autosomal recessive inheritance pattern. Three (42.9%, 3/7) variants were involved in the renin-angiotensin-aldosterone system (RAAS), which are the known genetic causes of autosomal recessive renal tubular dysgenesis (ARRTD). CONCLUSION: CMA has low diagnostic utility for oligohydramnios, while WES offers obvious advantages in improving the detection rate. WES should be recommended for fetuses with oligohydramnios.

CMA has low diagnostic utility for oligohydramnios.WES offers obvious advantages for improving the detection over CMA, which improves pregnancy management, prenatal counselling and recurrence risk assessment for future pregnancies.

A novel 1p13.2 deletion associates with neurodevelopmental disorders in a three-generation pedigree.

BACKGROUND: A multitude of studies have highlighted that copy number variants (CNVs) are associated with neurodevelopmental disorders (NDDs) characterized by a wide range of clinical characteristics. Benefiting from CNV calling from WES data, WES has emerged as a more powerful and cost-effective molecular diagnostic tool, which has been widely used for the diagnosis of genetic diseases, especially NDDs. To our knowledge, isolated deletions on chromosome 1p13.2 are rare. To date, only a few patients were reported with 1p13.2 deletions and most of them were sporadic. Besides, the correlation between 1p13.2 deletions and NDDs remained unclear. CASE PRESENTATION: Here, we first reported five members in a three-generation Chinese family who presented with NDDs and carried a novel 1.41 Mb heterozygous 1p13.2 deletion with precise breakpoints. The diagnostic deletion contained 12 protein-coding genes and was observed to segregate with NDDs among the members of our reported family. Whether those genes contribute to the patient's phenotypes is still inconclusive. CONCLUSIONS: We hypothesized that the NDD phenotype of our patients was caused by the diagnostic 1p13.2 deletion. However, further in-depth functional experiments are still needed to establish a 1p13.2 deletion-NDDs relationship. Our study might supplement the spectrum of 1p13.2 deletion-NDDs.

Exome sequencing in fetuses with short long bones detected by ultrasonography: A retrospective cohort study.

Background: Prenatal diagnosis of fetal short long bones (SLBs) was reported to be associated with skeletal dysplasias, chromosomal abnormalities, and genetic syndromes. This study aims to identify the genetic causes for fetal short long bones, and retrospectively evaluate the additional diagnostic yield of exome sequencing (ES) for short long bones following the use of conventional genetic testing. Methods: A cohort of ninety-four fetuses with sonographically identified short long bones was analyzed by trio-exome sequencing between January 2016 and June 2021. Fetuses with abnormal results of karyotype or chromosomal microarray analysis were excluded. Variants were interpreted based on ACMG/AMP guidelines. All diagnostic de novo variants were validated by Sanger sequencing. Results: Of the 94 fetuses, 38 (40.4%) were found to carry causal genetic variants (pathogenic or likely pathogenic) in sixteen genes with 38 variants. Five fetuses (5.3%) had variant(s) of uncertain significance. Thirty-five cases (37.2%) were diagnosed as genetic skeletal dysplasias including 14 different diseases that were classified into 10 groups according to the Nosology and Classification of Genetic Skeletal Disorders. The most common disease in the cohort was achondroplasia (28.9%), followed by osteogenesis imperfecta (18.4%), thanatophoric dysplasia (10.5%), chondrogenesis (7.9%), and 3-M syndrome (5.3%). The diagnostic yield in fetuses with isolated short long bones was lower than the fetuses with non-isolated short long bones, but not reached statistical significance (27.3% vs. 44.4%; p = 0.151). Whereas, the rate in the fetuses with other skeletal abnormalities was significantly higher than those with non-skeletal abnormalities (59.4% vs. 32.5%, p = 0.023), and the diagnostic rate was significantly higher in femur length (FL) below -4SDs group compared with FL 2-4SDs below GA group (72.5% vs. 16.7%; p < 0.001). A long-term follow-up showed that outcomes for fetuses with FL 2-4SDs below GA were significantly better than those with FL below -4SDs. Additionally, fourteen (36.8%) novel short long bones-related variants were identified in the present study. Conclusion: The findings suggest that in fetuses with short long bones routine genetic tests failed to determine the underlying causes, exome sequencing could add clinically relevant information that could assist the clinical management of pregnancies. Novel pathogenic variants identified may broaden the mutation spectrum for the disorders and contributes to clinical consultation and subsequent pregnancy examination.

Phelan-McDermid Syndrome in Pediatric Patients With Novel Mutations: Genetic and Phenotypic Analyses.

Background: PhelanrMcDermid syndrome (PMS) is an uncommon autosomal dominant inherited developmental disorder. The main characteristics are hypotonia, intellectual disability, autism spectrum disorder, autism-like behaviors and tiny facial deformities. Most cases are caused by the deletion of the 22q13 genomic region, including the deletion of SHANK3. Methods: Genetic and phenotype evaluations of ten Chinese pediatric patients were performed. The clinical phenotypes and genetic testing results were collected statistically. We analyzed the deletion of the 22q13 genomic region and small mutations in SHANK3 (GRCh37/hg19) and performed parental genotype verification to determine whether it was related to the parents or was a novel mutation. Results: The age of the patients diagnosed with PMS ranged from 0 to 12 years old. Nine of the pediatric patients experienced Intellectual Disability, language motion development delay and hypotonia as prominent clinical features. One subject had autism, two subjects had abnormal electroencephalogram discharge and one subject was aborted after fetal diagnosis. Three patients had a SHANK3 mutation or deletion. All but the aborted fetuses had intellectual disability. Among the ten patients, a deletion in the 22q13 region occurred in seven patients, with the smallest being 60.6 kb and the largest being >5.5 Mb. Three patients had heterozygous mutations in the SHANK3 gene. Conclusion: All ten patients had novel mutations, and three of these were missense or frameshift mutations. For the first time reported, it is predicted that the amino acid termination code may appear before protein synthesis. The novel mutations we discovered provide a reference for clinical research and the diagnosis of PMS.

Paternal De Novo Variant of TAOK1 in a Fetus With Structural Brain Abnormalities.

A dilated lateral ventricle is a relatively common finding on prenatal ultrasound, and the causes are complex. We aimed to explore the etiology of a fetus with a dilated lateral ventricle. Trio whole-exome sequencing was performed to detect causative variants. A de novo variant of TAOK1 (NM_020791.2: c.227A>G) was detected in the proband and evaluated for potential functional impacts using a variety of prediction tools. Droplet digital polymerase chain reaction was used to exclude the parental mosaicism and to verify the phasing of the de novo variant. Based on peripheral blood analysis, the parents did not exhibit mosaicism at this site, and the de novo variant was paternally derived. Here, we describe a fetus with a de novo likely pathogenic variant of TAOK1 who had a dilated lateral ventricle and a series of particular phenotypes. This case expands the clinical spectrum of TAOK1-associated disorders. We propose a method for solving genetic disorders in which the responsible genes have not yet gone through ClinGen curation, particularly for prenatal cases.

Next-generation sequencing facilitates genetic diagnosis and improves the management of patients with hearing loss in clinical practice.

BACKGROUND: Hearing loss (HL) is a prevalent sensorineural disorder, and is among the most etiologically heterogeneous disorders. With the advent of next-generation sequencing (NGS) technologies, hundreds of candidate genes can be analyzed simultaneously in a cost-effective manner. METHODS: Ninety-four patients from 87 families diagnosed with non-syndromic or syndromic HL were enrolled. A custom-designed HL panel and clinical exome sequencing (CES) were applied to explore molecular etiology in the cohort, and the efficacy of the two panels was examined. RESULTS: The etiologic diagnosis for HL has been identified for 36 out of 87 probands (41.4%), 28 with an autosomal recessive (AR) inheritance pattern and 8 with an autosomal dominant (AD) pattern. Candidate variants in 18 different genes were identified in the study cohort, 10 with AR inheritance pattern and 8 with AD pattern. Fourteen of the variants identified in the study were novel. CONCLUSIONS: The custom-designed HL panel covers almost all known HL-associated genes, and can be used as an effective clinical diagnostic platform; CES evaluates all exons related to clinical symptoms, and is also suitable for clinical diagnosis of HL. Next-generation sequencing facilitates genetic diagnosis and improves the management of patients with HL in the clinical practice.

A Retrospective Cohort Analysis of the Genetic Assay Results of Foetuses with Isolated and Nonisolated Umbilical Cord Cyst.

Objective: To analyse the risk of clinical chromosomal abnormalities in foetuses with umbilical cord cysts. Methods: Data from all genetic assays that were performed as part of invasive prenatal diagnoses of umbilical cord cysts between October 2014 and June 2021 were retrospectively collected from Guangdong Women and Children Hospital. We compared the differences in genetic assay findings in isolated and nonisolated umbilical cord cyst cohorts. Results: A total of 49 singleton pregnancies and 2 foetuses that were one of the cotwins in monochorionic twin pregnancies were enrolled in the cohort; 20 isolated and 31 nonisolated umbilical cord cysts were identified in the cohort. One foetus (5%, 1/20) in the isolated umbilical cord cyst group showed chromosomal abnormalities and 17p12 microduplication. Twelve cases (38.7%, 12/31) of chromosomal abnormalities, including seven cases of trisomy 18, two cases of trisomy 13 and three cases of microdeletion, were identified in the nonisolated umbilical cord cyst group. The incidences of chromosomal abnormalities between the two groups were significantly different (1/20, 5% vs 13/31, 38.7%, p=0.003). There was no relative pathological medical exome sequencing finding in the three foetuses suffering from nonisolated umbilical cord cysts whose parents chose to undergo chromosomal microarray analysis (CMA) and medical exome sequencing. Conclusion: This retrospective cohort study evaluated the value of CMA in foetuses with umbilical cord cysts and suggested that copy number variants (CNVs) may be the basic genetic aetiological factors that should be considered for diagnostic evaluation. We recommended CMA as a basic genetic evaluation in cases of umbilical cord cysts, especially in nonisolated cases.

Novel Biallelic Variant in the BRAT1 Gene Caused Nonprogressive Cerebellar Ataxia Syndrome.

Recessive mutations in BRAT1 cause lethal neonatal rigidity and multifocal seizure syndrome (RMFSL), a phenotype characterized by neonatal microcephaly, hypertonia, and refractory epilepsy with premature death. Recently, attenuated disease variants have been described, suggesting that a wider clinical spectrum of BRAT1-associated neurodegeneration exists than was previously thought. Here, we reported a 10-year-old girl with severe intellectual disability, rigidity, ataxia or dyspraxia, and cerebellar atrophy on brain MRI; two BRAT1 variants in the trans configuration [c.1014A > C (p.Pro338 = ); c.706delC (p.Leu236Cysfs*5)] were detected using whole-exome sequencing. RNA-seq confirmed significantly decreased BRAT1 transcript levels in the presence of the variant; further, it revealed an intron retention between exon 7 and exon 8 caused by the synonymous base substitute. Subsequent prenatal diagnosis for these two variants guided the parents to reproduce. We expand the phenotypic spectrum of BRAT1-associated disorders by first reporting the pathogenic synonymous variant of the BRAT1 gene, resulting in clinical severity that is mild compared to the severe phenotype seen in RMFSL. Making an accurate diagnosis and prognostic evaluation of BRAT1-associated neurodegeneration is important for reproductive consultation and disease management.

Two cases of microvillus inclusion disease caused by MYO5B deficiency with prenatal abnormalities.

BACKGROUNDS: Microvillus inclusion disease (MVID) characterizes as intractable life-threatening watery diarrhea malnutrition after birth. MATERIALS & METHODS: Here we describe two patients with prenatal ultrasound findings of bowel dilation or increased amniotic fluid volume presented intractable diarrhea after birth. Exome sequencing and Intestinal biopsy were performed for the patients and their parents to reveal the underlying causes. The mutations were verified by Sanger sequencing and quantitative polymerase chain reaction. RESULTS: Exome sequencing revealed that both of the patients carrying MYO5B compound heterozygote mutations that were inherited from their parents. CONCLUSION: Here we describe two cases with MVID caused by MYO5B deficiency, which was the most common caused with prenatal ultrasound findings of bowel dilation and increased amniotic fluid volume. Due to the lack of effective curative therapies, early diagnosis even in prenatal of MVID can provide parents with better genetic counseling on the fetal prognosis.

A spectrum of clinical severity of recessive titinopathies in prenatal.

Variants in TTN are associated with a broad range of clinical phenotypes, from dominant adult-onset dilated cardiomyopathy to recessive infantile-onset myopathy. However, few foetal cases have been reported for multiple reasons. Next-generation sequencing has facilitated the prenatal identification of a growing number of suspected titinopathy variants. We investigated six affected foetuses from three families, completed the intrauterine course of the serial phenotypic spectrum of TTN, and discussed the genotype-phenotype correlations from a broader perspective. The recognizable prenatal feature onset at the second trimester was started with reduced movement, then contracture 3-6 weeks later, followed with/without hydrops, finally at late pregnancy was accompanied with polyhydramnio (major) or oligohydramnios. Two cases with typical arthrogryposis-hydrops sequences identified a meta-only transcript variant c.36203-1G>T. Deleterious transcriptional consequences of the substitution were verified by minigene splicing analysis. Case 3 identified a homozygous splicing variant in the constitutively expressed Z-disc. It presented a milder phenotype than expected, which was presumably saved by the isoform of corons. A summary of the foetal-onset titinopathy cases implied that variants in TTN present with a series of signs and a spectrum of clinical severity, which followed the dosage/positional effect; the meta-only transcript allele involvement may be a prerequisite for the development of fatal hydrops.

A novel non-sense variant in the OFD1 gene caused Joubert syndrome.

Background: Joubert syndrome (JBS) is a rare neurodevelopmental disorder associated with progressive renal, liver, and retinal involvement that exhibits heterogeneity in both clinical manifestations and genetic etiology. Therefore, it is difficult to make a definite prenatal diagnosis. Methods: Whole-exome sequencing and Sanger sequencing were performed to screen the causative gene variants in a suspected JBS family. RNA-seq and protein model prediction were performed to clarify the potential pathogenic mechanism. A more comprehensive review of previously reported cases with OFD1 variants is presented and may help to establish a genotype-phenotype. Results: We identified a novel non-sense variant in the OFD1 gene, OFD1 (NM_003611.3): c.2848A>T (p.Lys950Ter). Sanger sequencing confirmed cosegregation among this family. RNA-seq confirmed that partial degradation of mutant transcripts, which was predicted to be caused by the non-sense-mediated mRNA decay (NMD) mechanism, may explain the reduction in the proportion of mutant transcripts. Protein structure prediction of the non-sense variant transcript revealed that this variant may lead to a change in the OFD1 protein structure. Conclusion: The genetic variation spectrum of JBS10 caused by OFD1 was broadened. The novel variants further deepened our insight into the molecular mechanism of the disease.

A Multidisciplinary Approach in Prenatal Diagnosis of TSC With Cardiac Rhabdomyoma as the Initial Symptom.

The long-term prognosis of a fetus with cardiac rhabdomyoma (CR) depends on the correlation with tuberous sclerosis complex (TSC). In recent years, the numerous variations of uncertain significance (VUS) of TSC genes produced by high-throughput sequencing have made counseling challenging, studies until now have tended to side-step the tricky topics. Here, we integrated detailed parental phenotype, echocardiography, neuro MRI, and genetic information to conduct a comprehensive evaluation of 61 CR fetuses. As a result, multiple CRs and cerebral lesions appeared in 90 and 80%, respectively of fetuses with pathogenic (P)/likely pathogenic (LP) TSC1/TSC2 variations. Overall, 85.7% of the live-born infants with P/LP presented with TSC-associated signs. While, 85.7% of VUS without nervous findings had good prognoses. Genetic evidence and cerebral MRI findings are the most sensitive index to assess long-term prognosis, which complement and confirm each other for a TSC diagnosis. In total, 68.9% of fetuses with CR could benefit from this multidisciplinary approach, which turned out to be potentially clinically actionable with precise clinical/genetic diagnosis or had a foreseeable outcome. Our practice provides a practical and feasible solution for perinatal management and prognostic guidance for fetuses with CR.

Prenatal genetic diagnosis of omphalocele by karyotyping, chromosomal microarray analysis and exome sequencing.

OBJECTIVES: The aim of this study is to share our experience in the prenatal diagnosis of omphalocele by karyotyping, chromosomal microarray analysis (CMA) and whole exome sequencing (WES). METHODS: In this retrospective study, 81 cases of omphalocele were identified from 2015 to 2020. Associated anomalies and prenatal diagnosis based on karyotyping, CMA and WES were analysed. RESULTS: Fifty-eight (71.6%) of the 81 foetuses had other ultrasound anomalies. Giant omphalocele was present in 11 cases (13.6%) and small omphalocele was present in 70 cases (86.4%). Chromosomal abnormalities were found in 24 foetuses (29.6%, 24/81), the most common of which were trisomy 18 (58.8%, 11/24) and trisomy 13 (29.2%, 7/24). Compared to isolated omphalocele, non-isolated omphalocele was accompanied by an increased prevalence of chromosomal abnormalities (4.3% (1/23) vs. 39.7% (23/58), χ2 = 8.226, p = .004). All chromosomal abnormalities were found in small omphalocele. Aside from aneuploidy, CMA showed one pathogenic copy number variants (CNVs) for a detection rate of 1.2%, one variants of unknown significance (VOUS) and one instance of loss of heterozygosity (LOH). WES was performed on 3 non-isolated cases, and one was found to have pathogenic variants. CONCLUSIONS: The most common genetic cause of omphalocele is aneuploidy and the prevalence of chromosomal abnormalities is increased with non-isolated and small omphalocele. CMA and WES can be useful for providing further genetic information to assist in prenatal counselling and pregnancy management.

A Novel Multi-Exon Deletion of PACS1 in a Three-Generation Pedigree: Supplements to PACS1 Neurodevelopmental Disorder Spectrum.

PACS1 neurodevelopmental disorder (PACS1-NDD) is a category of rare disorder characterized by intellectual disability, speech delay, dysmorphic facial features, and developmental delay. Other various physical abnormalities of PACS1-NDD might involve all organs and systems. Notably, there were only two unique missense mutations [c.607C > T (p.Arg203Trp) and c.608G > A (p.Arg203Gln)] in PACS1 that had been identified as pathogenic variants for PACS1-NDD or Schuurs-Hoeijmakers syndrome (SHMS). Previous reports suggested that these common missense variants were likely to act through dominant-negative or gain-of-function effects manner. It is still uncertain whether the intragenic deletion or duplication in PACS1 will be disease-causing. By using whole-exome sequencing, we first identified a novel heterozygous multi-exon deletion covering exons 12-24 in PACS1 (NM_018026) in four individuals (two brothers and their father and grandfather) in a three-generation family. The younger brother was referred to our center prenatally and was evaluated before and after the birth. Unlike SHMS, no typical dysmorphic facial features, intellectual problems, and structural brain anomalies were observed among these four individuals. The brothers showed a mild hypermyotonia of their extremities at the age of 3 months old and recovered over time. Mild speech and cognitive delay were also noticed in the two brothers at the age of 13 and 27 months old, respectively. However, their father and grandfather showed normal language and cognitive competence. This study might supplement the spectrum of PACS1-NDD and demonstrates that the loss of function variation in PACS1 displays no contributions to the typical SHMS which is caused by the recurrent c.607C > T (p.Arg203Trp) variant.

Severe fetal anemia and hydrops fetalis associated with compound heterozygosity for Hb Zurich-Albisrieden (HBA2:c.178G>C) and Hb Quong Sze (HBA2:c.377T>C).

We report on a fetus with cardiomegaly and increased middle cerebral artery-peak systolic velocity at 25 weeks of gestation. Severe fetal anemia (hemoglobin (Hb) level 37 g/L) was confirmed by cordocentesis. Hb analysis showed that Hb Bart's was 9% in cord blood. Molecular analysis of the proband's family found that the mother was a carrier of Hb Quong Sze (Hb QS, HBA2:c.377T>C), the father was a carrier of Hb Zurich-Albisrieden (Hb ZA, HBA2:c.178G>C), and the fetus was a compound heterozygote for Hb ZA and Hb QA. Despite intrauterine blood transfusions, the fetus experienced problems including oligohydramnios, growth retardation, placental thickening, and heart enlargement in the third trimester. The couple chose to terminate the pregnancy, and fetal autopsy confirmed the above diagnosis. This is the first report of a case of Hb ZA compounded with Hb QS, and provides a reference for genetic counselling and prenatal diagnosis in the Chinese population.

[Analysis of clinical feature and genetic basis of a rare case with Olmsted syndrome].

OBJECTIVE: To analyze the clinical and genetic characteristics of a patient featuring autosomal dominant Olmsted syndrome. METHODS: Clinical features of the patient was reviewed. High-throughput sequencing was carried out to detect potential genetic variants. RESULTS: The proband, a 12-year-old girl, featured excessive keratinization on hands and feet, contracture of finger joints, and abnormal position and residual contraction of the fifth toes. Skin biopsy showed significant hyperkeratosis, epidermal hyperplasia, and mild interepidermal cell edema. A de novo heterozygous missense variant c.2016G>T(p.Met672Ile) was identified in the TRPV3 gene by high-throughout sequencing. The result was verified by Sanger sequencing. CONCLUSION: The destructive palmoplantar keratosis in the child may be attributed to the c.2016G>T(p.Met672Ile) variant of the TRPV3 gene. Aboving finding has provided new evidence for the correlation of genetic variants with clinical phenotypes of Olmsted syndrome.