[Expert consensus on the prenatal diagnosis and genetic counseling for uniparental disomy-related imprinting disorders].

Uniparental disomy (UPD)-related imprinting disorders are a group of congenital disorders which can lead to severe birth defects. Their molecular etiology is the occurrence of UPD in the genomic imprinting regions, which may cause disturbed expression of parent-of-origin imprinted genes. With the widespread applications of genetic testing techniques, the prenatal diagnosis of UPD-related imprinted diseases has gradually become clinical routines. However, due to the complicated pathogenesis of such disorders, currently there is still a lack of standards and norms for the understanding, diagnosis, management and genetic counseling. By referring to the relevant guidelines and consensus, the latest progress of research, and opinions from experts in the relevant fields, the writing group has formulated a consensus over the prenatal diagnosis and genetic counseling for UPD-related imprinting disorders, with an aim to provide a more accurate and rational evaluation in prenatal clinics.

[Clinical and genetic analysis of ten Chinese pedigrees affected with 7q11.23 duplication syndrome].

OBJECTIVE: To analyze the clinical and genetic characteristics of ten Chinese pedigrees affected with 7q11.23 duplication syndrome. METHODS: From December 2017 to January 2022, ten pedigrees diagnosed with 7q11.23 duplication syndrome at the First Affiliated Hospital of Zhengzhou University were enrolled as the study subjects. Clinical data of all subjects were collected, and some had subjected to copy number variation sequencing or single nucleotide polymorphism array to analyze the pattern of inheritance. RESULTS: The probands had included six fetuses and four adolescents. Four of the six prenatal cases showed abnormal ultrasound indicators, including three with soft indicators and one with abnormal fetal structural development. The clinical phenotype of the four adolescent cases had included mental retardation, delayed language development, and attention deficit hyperactivity disorder. The size of the copy number variations had ranged from 1.31 to 1.42 Mb, involving the classic region of 7q11.23 duplication syndrome. Of these, five cases had undergone parental origin testing, three cases were de novo, and two were hereditary. CONCLUSION: Individuals with 7q11.23 duplication syndrome may show substantial clinical phenotypic heterogeneity, hence the affected families should be provided with pre-pregnancy consultation and reproductive guidance.

[The value of combined CNV-Seq and chromosomal karyotyping for the detection of amniocytic mosaicisms and a literature review].

OBJECTIVE: To assess the value of combined copy number variation sequencing (CNV-seq) and chromosomal karyotyping for the diagnosis of amniocytic mosaicisms, in addition with a literature review. METHODS: Forty cases of amniocytic mosaicisms detected at the Genetic and Prenatal Diagnosis Center of the First Affiliated Hospital of Zhengzhou University from January 2018 to December 2021, in addition with 245 mosaicisms retrieved from 11 recent literature were evaluated in terms of detection rate, consistency rate, and pregnancy outcomes. RESULTS: The detection rate of amniocytic mosaicisms was 0.46% (40/8 621) in our center. And its consistency rate with chromosomal karyotyping was 75.0% (30/40). After genetic counseling, 30 (75.0%) couples had opted to terminate the pregnancy, 5 (12.5%) had decided to continue with the pregnancy, 3 (7.5%) fetuses were born alive, and 2 cases (5.0%) were lost in touch. By contrast, 245 cases (0.39%) of mosaicisms were identified among 63 577 amniotic samples, with a consistency rate of 62.8% (103/164) with other techniques. Among these, 114 cases (55.1%) were terminated, 75 (36.2%) were born alive, and 18 (8.7%) were lost during the follow up. CONCLUSION: Combined CNV-seq and chromosomal karyotyping has a high value for the detection of amniotic mosaicisms.

[Clinical phenotype and genetic analysis of a patient with a heterozygous 6p25.3 deletion and partial trisomy 15q].

OBJECTIVE: To investigate the clinical phenotype and genetic characteristics of a patient with a heterozygous 6p25.3 deletion and partial trisomy 15q. METHODS: A patient who had presented at the Genetics and Prenatal Diagnosis Center of the First Affiliated Hospital of Zhengzhou University on May 14, 2021 was selected as the study subject. Clinical data of the patient was collected, and G-banded chromosomal karyotyping and copy number variation sequencing (CNV-seq) were carried out. RESULTS: The patient's main clinical features have included complete uterine septum, vaginal septum, atrophy of left eyeball, abnormal fingers and toes, and mental retardation. The karyotype of the patient was 46,XX,der(6)t(6;15)(p25.3;q26.1). CNV-seq result has indicated a 1.20 Mb heterozygous deletion in the 6p25.3 region and a 10.20 Mb duplication in the 15q26.1q26.3 region. The deletion segment has included the FOXQ1 gene, which may be related with the abnormal development of the left eye. The duplication segment has a 96.16% overlap with the region associated with 15q26 overgrowth syndrome (including the IGF1R gene), which may be related to the patient' s abnormal development of the Müllerian duct, abnormal fingers and toes, and mental developmental delay. CONCLUSION: The heterozygous deletion of the 6p25.3 region and duplication of the 15q26.1q26.3 region probably underlay the abnormal clinical phenotype in this patient.

[Analysis of genome copy number variations in fetuses with isolated ventricular septal defect and a literature review].

OBJECTIVE: To assess the value of copy number variation sequencing (CNV-seq) for revealing the genetic etiology of fetuses with isolated ventricular septal defect (VSD). METHODS: From December 2017 to December 2020, 69 fetuses with isolated VSD were identified at the First Affiliated Hospital of Zhengzhou University. Meanwhile, 839 similar prenatal cases were selected from public databases including Wanfang data, Wanfang Medicine, and China National Knowledge Infrastructure (CNKI) by using keywords such as "Ventricular septal defect", "Copy number variation", and "Prenatal". A total of 908 fetuses with isolated VSD were analyzed. CNV-seq was carried out for 69 fetuses. RESULTS: Among the 908 fetuses, 33 (3.63%) were found to harbor pathogenic CNVs, which included 11 chromosomal aneuploidies (1.21%) and 22 pathogenic CNVs (2.42%). The pathogenic CNVs have involved 12 genetic syndromes, with those known to involve the heart development including 5 cases of 22q11.21 deletion syndrome, 2 cases of 4q terminal deletion syndrome, and 1 case of 9q subtelomere deletion syndrome. The outcome of pregnancies for 15 fetuses with pathogenic CNVs was known, of which 12 were terminated, and 3 had spontaneous closure of the ventricular septum after birth, but 1 of them had other abnormalities. CONCLUSION: Fetuses with isolated VSD have a relatively high risk for chromosomal abnormalities, for which CNV-seq should be recommended.

The uncertainty of copy number variants: pregnancy decisions and clinical follow-up.

BACKGROUND: Next-generation sequencing for copy number variants is often used as a follow-up investigation of unusual fetal ultrasound results and is capable of detecting copy number variations with a resolution of ∼0.1 Mb. In a prenatal setting, observation and subsequent management of pregnancies with a fetal variant of uncertain significance remains problematic for counseling. OBJECTIVE: This study aimed to follow the decision-making processes in pregnancies with a fetal variant of uncertain significance and prospectively assess copy number variation interpretations and implications under the newer 2020 American College of Medical Genetics and Genomics guidelines. STUDY DESIGN: In a single prenatal unit, prospective chromosome testing using copy number variation sequencing for 8030 fetuses with unexpected noninvasive findings identified 139 pregnancies with a copy number variation classified as a variant of uncertain significance according to the 2015 American College of Medical Genetics and Genomics guidelines current at the time. Parent-of-origin testing was subsequently performed to determine if the copy number variation was inherited or de novo. All couples were offered specialized genetic counseling to assist in pregnancy management decisions. For the continued pregnancies that reached term, newborns were clinically assessed for evidence of any disease at 0 to 10 months and/or at 2 to 4 years of age. RESULTS: Of the 139 variants of uncertain significance found, most (78%) were inherited with no evidence of disease in the carrier parent. On the basis of primary ultrasound findings combined with results from noninvasive prenatal screening tests, most inherited variant of uncertain significance pregnancies were continued, whereas most pregnancies involving de novo variants of uncertain significance were terminated. From clinical follow-up of the 113 live births, only 5 showed any evidence of a phenotype that was not apparently related to the original variant of uncertain significance. Prospective reanalysis of the 139 variants of uncertain significance using recent 2020 American College of Medical Genetics and Genomics guidelines changed the status of 24 variants of uncertain significance, with 15 reclassified as benign and 9 as pathogenic. However, the 5 children born with an inherited variant of uncertain significance reclassified as pathogenic showed no evidence of a disease phenotype on clinical follow-up. CONCLUSION: The severity of fetal ultrasound findings combined with results from parent-of-origin testing were the key drivers in pregnancy management decisions for patients. According to birth outcomes from continued pregnancies, most variants of uncertain significance proved to be apparently benign in nature and potentially of low risk of adverse disease outcome. There was a discordance rate of 17% for variant of uncertain significance scoring between the 2015 and 2020 American College of Medical Genetics and Genomics guidelines for defining a variant of uncertain significance, suggesting that difficulties remain for predicting true pathogenicity. Nonetheless, with increasing knowledge of population copy number variation polymorphisms, and a more complete assessment for alternative genetic causes, patients having prenatal assessments should feel less anxious when a fetal variant of uncertain significance is identified.

Estimate of genetic variants using CNV-Seq for fetuses with oligohydramnios or polyhydramnios.

BACKGROUND: Oligohydramnios or polyhydramnios, is associated with chromosomal aberrations, particularly aneuploidy. However, its correlation with copy number variation (CNV) remains unclear. METHODS: We retrospectively analyzed 428 cases with an abnormal level of amniotic fluid, comprising of 139 cases of single ultrasound findings (SU group) and 289 cases of multiple ultrasound findings (MU group), by CNV sequencing (CNV-Seq) and followed their pregnancy outcomes. RESULTS: The overall detection rate of clinically significant findings was 8%, with 5% in the SU group and 11% in MU group. Besides, 18 microdeletion/microduplication syndromes were detected, with the highest rate of renal cysts and diabetes syndrome (22%, 4/18). Also, the rate of termination of pregnancy in MU group was much higher than that in the SU group (29% vs. 10%, ***p < 0.001), and in the MU-oligohydramnios subgroup, it was the highest (34%), regardless of cases with chromosomal anomaly and lost to follow-up. CONCLUSION: Our results showed that the abnormal level of amniotic fluid, especially combined with other ultrasound abnormalities, is closely related to chromosomal abnormalities and genetic CNVs. CNV-Seq may be useful in investigating pregnancies with an abnormal amniotic fluid level.

[Clinical and genetic analysis of a child with mosaic chromosome 8 trisomy syndrome].

OBJECTIVE: To explore the genetic etiology of a child featuring recurrent oral ulcer. METHODS: Clinical data of the child was collected. Whole exome sequencing was carried out for her. Candidate variant was verified by low-coverage massive parallel copy number variation sequencing (CNV-seq) of the family trio. RESULTS: The child, a 6-year-old girl, has featured recurrent fever and ulcers of the oral mucosa, vulvar and perianal regions. No pathogenic variant was found by whole exome sequencing. However, analysis of chromosome copy number variation using the whole exome sequencing data has revealed mosaicism of trisomy 8. CNV-seq assay has verified the variant in the child, with the percentage of mosaicism being 73%. No abnormality was found in neither of her parents. CONCLUSION: A case of mosaicism trisomy 8 with recurrent oral ulcer as the first symptom was diagnosed, which has enriched the phenotypic data of trisomy 8 syndrome.

[Prenatal diagnosis of partial deletion of NRXN1 gene with combined CNV-seq and qPCR assays].

OBJECTIVE: To summarize the genetic diagnosis, low-depth copy number variation sequencing (CNV-seq) and prenatal finding in 7 fetuses with 2p16.3 deletions only involving the NRXN1 gene. METHODS: The 7 fetuses have all been found to have loss of heterozygosity at 2p16.3 by CNV-seq, which were verified by quantitative real-time PCR (qPCR). Specific regions of NRXN1 gene deletions were identified, and the CNVs were verified in their parents. Outcome of the pregnancies were followed up. RESULTS: Among 16 502 prenatal samples, 7 fetuses were found to harbor a 120 kb ~ 900 kb microdeletion in the 2p16.3 region, which yielded a prevalence of 0.424‰. The deleted region mainly involved 50 200 000-51 880 000 positions of chromosome 2 and involved only the NRXN1 gene. All of the 7 fetal CNVs were confirmed by qPCR, including 2 cases with heterozygous deletion of exons 1 to 6, 1 with heterozygous deletion of exons 1 to 19, 1 with heterozygous deletion of exons 19 to 22, and 3 with heterozygous deletion of introns 6 to 7 of the NRXN1 gene. Verification in the parents had found that one deletion was inherited from the father, 1 was from the mother, 2 cases were de novo in origin, whilst the remaining 3 had refused parental verification. After genetic counseling, one couple had elected induced abortion, 1 case has not been born yet, whilst the other 5 cases were born healthy. Follow up had identified no mental abnormalities among the children. CONCLUSION: Seven fetuses with heterozygous 2p16.3 deletions only involving the NRXN1 gene were detected by CNV-seq. The specific deletion of the NRXN1 gene was verified by qPCR. Prenatal genetic counseling and fertility guidance has been provided to the particular family by combining the results of CNV testing, pedigree analysis and pregnancy outcome.

[Genetic analysis and prenatal diagnosis for a Chinese pedigree affected with Bainbridge-Ropers syndrome].

OBJECTIVE: To explore the clinical features and genetic basis for a child with Bainbridge-Ropers syndrome (BRPS). METHODS: Clinical data of the child were retrospectively analyzed. Copy number variation sequencing (CNV-seq) and trio based whole exome sequencing (trio-WES) were carried out. Prenatal diagnosis was provided for a at risk fetus from the pedigree, and genotype phenotype correlation was summarized through a literature review. RESULTS: The proband, a 6-year-old boy, has presented with feeding difficulties, specific craniofacial features, global developmental delay and intellectual disability, which has not improved after rehabilitation treatment. CNV-seq analysis of the patient showed no obvious abnormalities. A de novo heterozygous truncating variation, c.1448dupT (p.T484Nfs*5), was identified in the ASXL3 gene by trio-WES, which was a previously reported pathogenic variant. So far 14 Chinese patients with BRPS and ASXL3 variants have been reported. All patients have shown specific craniofacial features and delayed motor and speech development, and harbored 12 loss of function ASXL3 variants, which were de novo in origin and have clustered in exons 11 and 12 of the ASXL3 gene. CONCLUSION: The heterozygous frameshift c.1448dupT (p.T484Nfs*5) variant of the ASXL3 gene probably underlay the disorder in this patient. BRPS should be considered in infants with feeding difficulties, special craniofacial features, global developmental delay and hand anomalies, and WES can help to delineate the pathogenesis and establish the definite diagnosis.

[CNV-seq analysis of copy number variations in 217 fetuses with nasal bone dysplasia].

OBJECTIVE: To assess the diagnostic value of copy number variation sequencing (CNV-seq) in the genetic etiology of fetuses with nasal bone dysplasia (NBD). METHODS: A total of 217 fetuses discovered with NBD from December 2017 to December 2020 were divided into the isolated NBD group and NBD combined with other anomalies group, for which copy number variations (CNVs) were analyzed. RESULTS: A total of 40 fetal abnormalities were detected in 217 cases, with an overall abnormal rate of 18.4%. These included 31 cases with aneuploidies (14.3%, 31/217) and 9 cases with genomic CNVs (4.1%, 9/217). Five cases of trisomy 21 (3.5%, 5/144) and two CNVs cases with unknown clinical significance (1.4%, 2/144) were detected in the isolated group. As for the combined NBD group, 26 aneuploidies (35.6%, 26/73), including 19 cases with trisomy 21, 6 cases with trisomy 18, 1 case with trisomy 13, 5 cases with pathogenic CNVs (6.8%, 5/73), and 2 cases with CNVs of unknown clinical significance (2.7%, 2/73) were detected. A significant difference was detected between the two groups (P < 0.01). CONCLUSION: The detection rate of CNV-seq is high for chromosomal aneuploidies and pathogenic CNVs in fetuses with NBD, particularly in those combined with other ultrasonic abnormalities.

[Analysis of chromosomal copy number variations among 163 fetuses with echogenic bowel by using CNV-seq technology].

OBJECTIVE: To assess the value of low-depth whole-genome copy number variation sequencing (CNV-seq) for the analysis of chromosomal copy number variations among fetuses with echogenic bowel (EB). METHODS: A total of 163 fetuses were included in this study. Amniotic fluid (162 cases) or chorionic villi (1 case) were collected and subjected to CNV-seq for the analysis of CNVs. RESULTS: Thirteen (8.0%) pathogenic CNVs were detected, including 9 (5.5%) aneuploidies and 4 (2.4%) CNVs. The detection rate of the isolated EB group and combined EB group were 1.7% (1/58) and 11.4% (12/105), respectively. There was a significant difference between the two groups (P < 0.05). A Xp22.1 duplication was detected in both groups, and the fetuses were predicted as female DMD carriers and born healthy. Nine cases of aneuploidies and 2 (likely) pathogenic CNVs were identified in the combined EB group, all of them have warranted induced labor. CONCLUSION: The prevalence of chromosomal aneuploidies and pathogenic CNVs in fetuses with combined EB was much higher than isolated EB, and most of them may warrant termination of pregnancy. Compared with isolated EB, more attention should be paid to combined EB, for which prenatal diagnosis and genetic counseling should be carried out in time.

[Analysis of a case with Mowat-Wilson syndrome due to nonsense variant of ZEB2 gene].

OBJECTIVE: To explore the genetic basis for a girl with distinctive facial features, epilepsy, intellectual disability, chronic constipation and hypopigmentation of neck and upper extremities. METHODS: Whole exome sequencing was carried out for the proband. Candidate variant was verified by Sanger sequencing. RESULTS: The proband was found to harbor a heterozygous nonsense c.586G>T (p.Glu196*) variant of the ZEB2 gene, which was unreported previously. The variant was not detected in either parent. CONCLUSION: The ZEB2 gene c.586G>T (p.Glu196*) variant probably underlay the Mowat-Wilson syndrome in this patient. Hypopigmentation in the neck and upper extremities may be related to Mowat-Wilson syndrome. Prenatal diagnosis was recommended for subsequent pregnancies.

Genetic analysis and novel variation identification in Chinese patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

Congenital adrenal hyperplasia owing to 21-hydroxylase deficiency is an autosomal-recessive disorder caused by mutations in the CYP21A2 gene. The aim of the study was to analyze the molecular data of 155 21-OHD patients and retrospectively investigated the common allelic mutations of CYP21A2 in 1442 Chinese 21-OHD patients. Clinical features and mutations of CYP21A2 gene in 155 unrelated 21-OHD patients were examined. Of the 155 patients, 103 cases were salt-wasting (SW) forms, 38 were simple virilizing (SV) forms and 14 were non-classical (NC) forms. In general, two types of mutations including common allelic mutations (281/310, 90.6%) and rare mutations (29/310, 9.4%) were detected, among them four novel variants c.835G>T, c.1081C>T, c.1423C>T and c.651 + 2 T > G were identified. In 1442 Chinese 21-OHD patients, the most frequently mutations were I2G (36.2%), large deletion/conversion (20.7%) and p.I173N (17.8%), while p.V282L has the lowest frequency. In this study, we provided detailed clinical data and mutation spectrum in Chinese 21-OHD patients. Moreover, four novel CYP21A2 variants (c.835G>T, c.1081C>T, c.1423C>T and c.651 +2 T > G) were identified and computational structural modeling indicated that these novel variations probably affect structural stability. Our findings improve the understanding of CYP21A2 mutational spectrum and contribute to the precise diagnosis and prenatal counseling.

[Application of CNV-seq and chromosomal karyotyping in the prenatal diagnosis for carriers of balanced translocations].

OBJECTIVE: To assess the value of copy number variation sequencing (CNV-seq) and karyotyping in the prenatal diagnosis for carriers of balanced translocations. METHODS: Clinical records of 135 amniocentesis samples of balanced translocation carriers undergoing simultaneous CNV-seq and karyotyping were analyzed. Chromosomal aberrations were defined as those can definitely lead to birth defects definitely, which included chromosomal numerical abnormality, large deletion/duplication and pathogenic copy number variations (pCNVs). RESULTS: The detection rates for karyotyping and CNV-seq were 4.44% (6/135) and 5.93% (8/135) respectively, and the latter had a detection rate of 1.48(2/135) higher than the former. A total of 68 fetal chromosomal translocations were detected by karyotying analysis. CONCLUSION: For couples carrying a balanced translocation, simultaneous CNV-seq and karyotyping is conducive to the detection of fetal chromosomal abnormalities and genetic counseling.

Novel Partial Exon 51 Deletion in the Duchenne Muscular Dystrophy Gene Identified via Whole Exome Sequencing and Long-Read Whole-Genome Sequencing.

Duchenne muscular dystrophy (DMD), one of the most common progressive and severely disabling neuromuscular diseases in children, can be largely attributed to the loss of function of the DMD gene on chromosome Xp21.2-p21.1. This paper describes the case of a 10-year-old boy diagnosed with DMD. Whole exome sequencing confirmed the hypothesized large partial exonic deletion of c.7310-11543_7359del (chrX:g.31792260_31803852del) spanning exon 51 and intron 50 in DMD. This large deletion was verified to be de novo by PCR, and the two breakpoints were further confirmed by Sanger sequencing and long-read whole-genome sequencing. Notably, this partial exonic deletion was the only complex variation in the deep intron regions or intron-exon junction regions in DMD. In addition, the case study demonstrates the clinical importance of using multiple molecular genetic testing methods for the diagnosis of rare diseases.

[Clinical phenotype and genetic analysis of MECP2 duplication syndrome].

OBJECTIVE: To analyze the clinical symptom and parental origin of patients with MECP2 duplication syndrome in order to provide a basis for genetic counseling and prenatal diagnosis. METHODS: Clinical symptoms of four patients who were diagnosed with MECP2 duplication syndrome by copy number variation sequencing (CNV-Seq) were reviewed. The maternal origin of the duplications were verified. RESULTS: All patients were males, and CNV-Seq revealed that they have all harbored a duplication in the Xq28 region spanning 0.32 ~ 0.86 Mb, which were derived from asymptomatic mothers. The clinical symptoms of three patients with three copies included delayed speech, intellectual disability, and muscular hypotonia, while the patient with four copies had died at 6 months after birth, with clinical symptoms including recurrent infections, seizures, and spasticity. CONCLUSION: The four cases of MECP2 duplication syndrome have shown complete penetrance and have all derived from asymptomatic mothers. As a stable and reliable method, CNV-Seq can accurately detect the MECP2 duplication syndrome.

[Variant analysis of SEC23B gene in 4 families with congenital dyserythropoietic anemia].

OBJECTIVE: To identify the pathogenic variants of 4 patients with hemolytic anemia of unknown cause. METHODS: Peripheral blood samples of the patients and their family members were collected to extract DNA. The coding region and splice region in all exons of gene of erythrocyte related diseases were analyzed by using target sequence capture and high-throughput sequencing technology. Suspected pathogenic variants were verified by PCR combined Sanger sequencing technology. RESULTS: Each of the probands was detected two compound heterozygous variants, and CDA II was diagnosed. Six variants were detected in the 4 probands, four variants were reported and the other two were first reported. CONCLUSION: By high-throughput sequencing, gene variant of CDA II be analyzed fast and accurately. It is an effective supplement to convenional diagnostic methods. Furthermore, the novel variant sites have enriched the variant database of the SEC23B gene.

[Prenatal diagnosis and family analysis of 22q11.2 microdeletion syndrome].

OBJECTIVE: To analyze the prenatal diagnosis, parental verification and pregnancy outcome of 6 fetuses with 22q11.2 microdeletion syndrome. METHODS: Copy number variation sequencing (CNV-seq)and chromosomal microarray analysis (CMA) were carried out for the fetuses. RESULTS: The fetuses were found to harbor 2.54-3.2 Mb microdeletions of the 22q11.2 region, among which one was maternally inherited and one was paternally inherited. Two parents opted to continue with the pregnancy, and 4 chose induced labor. One fetus was found to have tetralogy of Fallot, while two carrier parents and one fetus appeared to have normal phenotype. CONCLUSION: 22q11.2 microdeletions identified upon prenatal diagnosis should be treated carefully, with ultrasonic scan and parental verification taken into account.

Novel mutations of the CYP17A1 gene in four Chinese 46,XX cases with partial 17a-hydroxylase/17,20-lyase deficiency.

The condition 17a-Hydroxylase/17,20-lyase deficiency (17-OHD) is a rare kind of congenital adrenal hyperplasia (CAH) characterized by failure to synthetize cortisol, adrenal androgens and gonadal steroids. Partial deficiency is much rarer, presenting with subtler symptoms. In this study, we summarized the clinical characteristics and identified the underlying gene mutation in four Chinese 46,XX patients with partial 17-OHD. Mutational analysis of the CYP17A1 gene was performed by polymerase chain reaction (PCR) and Sanger sequencing. Clinical and hormonal findings in these patients were consistent with typical manifestations of partial 17-OHD. All patients were found to have a compound heterozygous mutation of the CYP17A1 gene, with five mutations identified. Among them, c.887 T > C(p. I296T), c.1019G > A(p. R340H) and c.1346G > A(p. R449H) were novel missense mutations. In conclusion, we identified three novel missense mutations of the CYP17A1 gene from four patients with partial 17-OHD deficiency. Genotype-phenotype correlation analysis revealed that these novel mutations can lead to partial 17-OHD. Our findings thus provide novel insight into the clinical evaluations and molecular basis of 17-OHD.