45,X/46,XY Mosaicism. Contrast of prenatal and postnatal diagnosis

The process of prenatal diagnosis is unique in that the diagnosis and prognosis are made without seeing the patient. 45,X/46,XY mosaicism presents a special problem in this regard. The phenotype of 45,X/46,XY postnatally diagnosed children (pediatric group) was compared to that of 6 fetuses who were diagnosed from 7,000 amniocenteses (prenatal group). These amniocenteses were performed primarily because of an increased risk of chromosome abnormality. The pediatric group (age birth—18 yr) were all phenotypically abnormal, although none were mentally retarded. Seven patients presented with ambiguous genitalia, while 2 had primary amenorrhea. Sexual assignment was changed in 2. Abnormalities included rudimentary phallus, urogenital sinus, hypospadias, undescended testes, and short stature. All 9 patients required at least one surgical procedure. In contrast, the prenatally diagnosed fetuses (ages 3 months to 31/2 yr) were all phenotypically normal males. Four were noted to have male genitalia on ultrasonography. Thus, the phenotype of 45,X/46,XY mosaicism in prenatally diagnosed fetuses can be markedly different from that of individuals diagnosed postnatally. This must be considered when counseling patients.     

A 45,X/69,XXY fetus

Post-mortem examination of a 20-week fetus showed incompletely masculinised external genitalia, hypoplastic adrenal glands and minor physical stigmata suggestive of a chromosome abnormality. Gonad and skin were karyotyped and both were found to contain two cell lines, 45,X and 69,XXY. It appears this fetus is a true 45,X/69,XXY mosaic.     

Unilateral gonadal dysgenesis with both testis and fallopian tube on the same side in a 45,X/46,X INV (Y) mosaic male

A 5-year-old male with ambiguous external genitalia, hypospadias and microphallus without an urethral orifice was referred for cytogenetic studies. Exploratory laparotomy revealed presence of an infantile uterus and unilateral gonadal dysgenesis with both testes and fallopian tube on the right side. The metaphase cells from peripheral blood culture showed both 45,X/46,X inverted Y (p11.2q11.23) cell-lines (982). The inverted Y was found to be of paternal origin. Maternal chromosomal pattern was normal 46,XX. The presence of a fallopian tube next to testis suggest absence of secretion of anti-Mullerian hormone by Sertoli cells. The absence of Wolffian duct derivatives suggest insufficient secretion of testosterone by Leydig cells.     

Cell line segregation in a 45,X/46,XY mosaic child with asymmetric leg growth

Clinical evaluation of a 13 1/2-year-old male revealed a 4.4-cm leg length discrepancy and a small penis with a normal endocrine evaluation. Cytogenetic analysis of peripheral blood lymphocytes and skin fibroblasts derived from the back showed 45,X/46,XY mosaicism with similar percentages of 45,X cells, 36% and 30% respectively. However, two separate skin fibroblast cultures derived from the thigh and calf of the short (right) leg showed significant lack of Y-bearing cells with 100% and 80% 45,X, respectively. In contrast, skin biopsies of the thigh and calf of the normal (left) leg both showed 100% 46,XY. Similar evidence for differences in the percentages of Y-bearing cells in the left versus right leg fibroblast cultures was obtained using densitometric scanning of dot blots following DNA hybridization with a Y-specific probe at the DYZ4 locus. Asymmetric limb growth in cases of X/XY lymphocyte mosaicism warrants further cytogenetic investigation to substantiate possible genotype-phenotype correlations which may help uncover the fundamental growth deficiency in Turner syndrome.     

Monozygotic twins with 45,X/46,XY mosaicism discordant for phenotypic sex

We report on two sets of monozygotic twins (MZTs) discordant for phenotypic sex ascertained at birth when the female twin was noted to have signs of the Ullrich-Turner syndrome. Cytogenetic investigations on the female of the first pair showed 45,X/46,XY mosaicism in lymphocytes but fibroblasts grown from two skin biopsies at separate sites and from gonadal tissue showed only 45,X cells. The male showed mosaicism in both blood lymphocytes and skin fibroblasts. In the second family, both twins also showed mosaicism in lymphocytes. The female had a 45,X karyotype in fibroblasts from skin and gonadal tissue, but in contrast to the first family, the male twin had a normal male karyotype in fibroblasts from skin biopsy and from connective tissue adjacent to the vas deferens. Discordant phenotypic sex in monozygotic twins is rare. As in our cases, the nine previously reported sets of MZTs all had mosaicism for sex chromosome abnormalities. A mitotic error leading to the loss of a Y chromosome prior to, accompanying, or following the twinning process would account for the reported combinations of karyotypes. Am. J. Med. Genet. 75:40–44, 1998. © 1998 Wiley-Liss, Inc.     

Molecular study of 45,X conceptuses: Correlation with clinical findings

The parental origin of the single X in 45 cases (40 liveborns and 5 fetuses) with a 45, X karyo-type was studied using polymorphic DNA probes. The single X was paternal in origin (X^p) in 10 cases (22.2%) and maternal (X^m) in 35 cases (77.8%). Y chromosome material was detected in 1 out of the 35 cases with a 45, X^m constitution. Analysis of parental ages and clinical data of the patients with respect to the origin of the single X revealed no significant differences between the origins.     

新发睾丸决定基因SRY突变导致46,XY性发育异常三例

目的在46,XY性发育异常疾病(46,XY DSD)患者中进行SRY突变检测,分析其发生频率,并总结检出SRY突变患者的临床特点。方法纳入2009-2014年在北京协和医院内分泌科就诊的46,XY DSD患者63例,收集详细临床资料,提取外周血基因组DNA,PCR特异性扩增SRY并进行Sanger测序,通过与在线数据库比对确定突变,分析临床特点。结果 63例患者中共有三例检出SRY的3种新突变(约5%)。这三例患者社会性别均为女性,染色体核型为46,XY,有阴道和子宫结构,性激素符合高促性腺激素性性腺功能减退症。3种突变分别为:Pro131His、R76C和L35Afs*25。前2种错义突变位点位于HMG box核定位信号区,累及高度保守氨基酸,后1种为移码突变导致HMG box缺失,均严重破坏了SRY蛋白的重要功能结构域。结论该研究发现的3种SRY新突变是导致46,XY DSD的病因,SRY突变的检出率约为5%;对于46,XY DSD患者,建议均行SRY检测以明确病因。     

Infant with mos45,X/46,XY/47,XYY/48,XYYY: Genetic and clinical findings

We describe an infant with mos45,X/46,XY/47,XYY/48,XYYY who presented with ambiguous genitalia. Her phenotype was also remarkable for minor ear and eye anomalies and coarctation of the aorta with bicuspid aortic valve. Laparoscopy revealed bilateral Fallopian tubes and a left infantile testis with epididymis. Chromosomal analyses of blood, skin, aorta, right Fallopian tube, and left gonadal tissue showed mos45,X/46,XY/47,XYY/48,XYYY. The 46,XY cell line was identified with routine trypsin-Giemsa banding only in cultured cells from an aortic biopsy. Fluorescence in-situ hybridization (FISH) was utilized to identify the presence of 46,XY cells in other tissues. The clinical manifestations of this patient are discussed and compared with those of similar cases of Y chromosome aneuploidy. To our knowledge, this is the first report of a patient with this unusual karyotype. © 1995 Wiley-Liss, Inc.     

Mapping a gene for 46,XY gonadal dysgenesis by linkage analysis

46,XY gonadal dysgenesis was transmitted as an autosomal-dominant trait in a large family with multiple affected members. Expressivity of the trait was highly variable, ranging from pure to partial gonadal dysgenesis associated with normal female genitalia or sexual ambiguity, to mild hypospadias in otherwise normal males. The phenotypic features of this trait appeared to be confined to the genitourinary system. Multipoint parametric analysis using markers D5S664, D5S633, and D5D2102 yielded an LOD score of 4.47, assuming sex-limited, autosomal-dominant inheritance with a penetrance of 0.6. Because mutation in testis-determining genes leads to gonadal dysgenesis in 46,XY individuals, we postulate that the gene mapped by this study normally plays a role in gonadal differentiation.     

Embryonic testicular regression sequence: A part of the clinical spectrum of 46, XY gonadal dysgenesis

With the identification of the cystic fibrosis (CF) gene and its major mutations in 1989, there has been considerable debate among health professionals as to whether population-based carrier testing should be instituted. This paper presents the results of a survey to determine the attitudes of physicians and genetics professionals towards CF carrier testing. Factors associated with differences in attitudes also were examined. A questionnaire was mailed to primary care physicians and psychiatrists in 10 states who graduated from medical school between 1950 and 1985. For comparison, medical geneticists and genetic counselors in the same states also received the questionnaire. A total of 1,140 primary care physicians and psychiatrists (64.8%) and 280 medical geneticists and genetic counselors (79.1%) responded. Although 92% of respondents believed that a couple should be tested after asking about a test that detected 80% of carriers, only 43.9% of respondents believed such a test should be offered routinely. Those specialists most likely to have been involved in genetic services were most opposed to routine screening. The most important reason reported for opposition to routine screening was the consequences of an 80% detection rate. When presented with a hypothetical “error-free” test, 75.9% of respondents favored routine testing. Our findings suggest that there was little support for routinely offering the CF carrier test available at the time of this study among the physicians and professionals most involved in the provision of genetic services. © 1994 Wiley-Liss, Inc.     

Case of 45,X/46,XY mosaicism with non‐mosaic discordance between short‐term villi (45,X) and cultured villi (46,XY)

We report on a prenatally detected case of discordant non‐mosaic karyotypes following chorionic villus sampling. A 45,X karyotype was found in cytotrophoblast cells and a 46,XY karyotype in mesenchymal core cells. A subsequent amniocentesis showed a true 45,X/46,XY mosaicism. Confirmatory studies, including fluorescence in situ hybridization (FISH) in various fetal and placental tissues as well as in the original villi preparations changed the presumed condition of generalized mosaicism with culture confined normality to that of generalized mosaicism with absolute concordance. This case underscores the importance of the investigation of both short‐term and cultured villi preparations, the implementation of prenatal FISH studies, and the need for thorough follow‐up investigation in cases of discrepant results. Am. J. Med. Genet. 93:230–233, 2000. © 2000 Wiley‐Liss, Inc.     

An XXXY boy with X/XY half-sister

The clinical findings in a 13-year-old 48, XXXY boy are described. His half-sister (same mother) has a 45.X/XY karyotype. The X_g^a blood studies are compatible with his extra X's originating from the mother. These X_g^a studies and the IgM levels in the 48, XXXY boy raise the possibility of a gene-dosage effect for X-linked genes affecting these traits. The proband also has chronic pulmonary problems, an interesting association that has been noted with the Klinefelter syndrome, although usually in adults.     

A woman with an apparent non-mosaic 45,X delivered a 46,X,der(X) liveborn female

A liveborn female with a phenotype suggestive of Down syndrome is reported. Cytogenetic lymphocyte analysis showed a 46,X der(X) karyo-type. Fluorescence in situ hybridization (FISH) with a biotinylated probe specific for chromosome 21 showed no signal on the der(X). This marker was homogeneously painted using a specific probe for X chromosome. In addition, FISH analysis detected telomeres on the rearranged X. Therefore, the proband's karyotype was revaluated as 46,X,del(X) (pter p22.2::p11.3 qter). Cytogenetic analysis of 150 lymphocytes in the mother disclosed a homogeneous 45,X karyotype. FISH analysis of interphase nuclei using the X chromosome painting probe showed two domains of different sizes in 0.8% of cells. This led us to study further metaphases in the mother. In one out of 450 metaphases scored, after FISH with the X chromosome painting probe, the del(X) was observed, confirming that the rearranged X chromosome found in the newborn had segregated from a 45,X/46,X,del(X) mother.     

46,XY pure gonadal dysgenesis with non-fluorescent Y chromosome

A 46,XY karyotype with a non-fluorescent Y chromosome was found in an infantile girl aged 16 with primary amenorrhea. Identification of the Y chromosome was made by different staining techniques and a photometric scanning method. The histology of the streak gonad also indicated the Y character of the chromosome. The authors' interpretation is a 46,XY pure gonadal dysgenesis with a non-fluorescent Y chromosome.     

Association of deletion 9p, 46,XY gonadal dysgenesis and autistic spectrum disorder

Deletions of distal chromosome 9p24 are often associated with 46,XY gonadal dysgenesis and, depending on the extent of the deletion, the monosomy 9p syndrome. We have previously noted that some cases of 46,XY gonadal dysgenesis carry a 9p deletion and exhibit behavioural problems consistent with autistic spectrum disorder. These cases had a small terminal deletion of 9p with limited or no somatic anomalies that are characteristic of the monosomy 9p syndrome. Here, we present a new case of 46,XY partial gonadal dysgenesis and autistic spectrum disorder associated with a de novo deletion of 9p24 that was detected by ultra-high resolution oligo microarray comparative genomic hybridization. The deletion included the candidate sex-determining genes in the region DMRT1 and DMRT3. These data suggest that a gene responsible for autistic spectrum disorder is located within 9p24. It remains to be determined if the gonadal dysgenesis and autistic spectrum disorder are caused by a single gene or if they are caused by distinct genetic entities at 9p24.     

Cystic hygroma and 45,X/46,XY mosaicism

We report a case of fetal cystic hygroma with 45,X/46,XY mosaicism.     

Cytogenetic studies of a male with sporadic intestinal lymphangiectasia: 45,X/46,XY mosaicism with pseudo- and hyperdiploid subpopulations in cultured tissues

45,X/46,XY mosaicism was found in peripheral blood, bone marrow, and tissue cultures of an adult male with intestinal lymphangiectasia (IL). Turner phenotype was not present; his meiotic metaphase analysis was normal, and his dermatoglyphics resembled those of his family. Ten separate tissue culture lines from three biopsies of skin and thyroid gland contained 45,X cells (14.8 to 78.3%). Autosomal aneuploidy, resulting in pseudo- or hyperdiploidy, was also present in 4.3 to 41.6% of the cells. A hyperdiploid clone with a 47,X,+10,+18 karyotype was found in 22.6% of cells in one line. A second hyperdiploid clone with a 48,X,+2,+18,+18 karyotype occurred in 7.6% of cells from another line containing a total of 41.6% pseudo- and hyperdiploid cells. Such clonal abnormalities were not typical of tissue cultures from other patients done in our laboratory. Growth of our patient's tissue cultures was subnormal, and none proliferated beyond the fourth subculture. The significance of this observation remains to be determined. Our results do not allow us to conclude whether our patient's mosaicism of somatic tissues arose during embryogenesis, or whether it originated post-natally. The secondary immunodeficiency which occurs in IL may explain persistence of cells with unusual combinations of autosomal aneuploidy in our patient's tissues.