45,X/47,XYY mosaicism: clinical discrepancy between prenatally and postnatally diagnosed cases

Clinical and gonadal features and early surgical management of 45,X/46,XY and 45,X/47,XYY chromosomal mosaicism presenting with genital anomalies

OBJECTIVE

The 45,X/46,XY and 45,X/47,XYY group of patients includes some of those previously diagnosed with 'mixed gonadal dysgenesis'. Our aim was to establish the clinical and gonadal spectrum, and early surgical management, of patients with chromosomal mosaicism presenting with genital anomalies.

PATIENTS AND METHODS

We performed a retrospective review of patients with 45,X/46,XY or 45,X/47,XYY mosaicism presenting with genital ambiguity between 1988 and 2009. At least one gonadal biopsy or gonadectomy specimen was available for each patient. Gonadal histology was re-evaluated by a paediatric pathologist.

RESULTS

Of 31 patients with 45,X/46,XY (n = 28) or 45,X/47,XYY (n = 3) mosaicism and genital anomalies, 19 (61%) were raised male. Histology of 46 gonads was available from patients who had undergone a gonadectomy or gonadal biopsy, at a median age of 9.5 months. 18 gonads were palpable at presentation, including 5 (28%) histologically unremarkable testes, 2 streak gonads, and 1 dysgenetic gonad with distinct areas of testicular and ovarian stroma but no oocytes. All intra-abdominal gonads were found to be dysgenetic testes (of which 2 were noted to have pre-malignant changes) or streaks, apart from 1 histologically unremarkable testis. 15 (48%) patients had other anomalies, most commonly cardiac and renal; 4 (13%) had a Turner phenotype.

CONCLUSION

The anatomy and gonadal histology of 45,X/46,XY and 45,X/47,XYY individuals with genital ambiguity do not conform to a set pattern, and hence management of each patient should be individualized according to detailed anatomical and histological assessment.

Experts' opinions on the benefit of an incidental prenatal diagnosis of sex chromosomal aneuploidy: a qualitative interview survey

OBJECTIVE

Incidental findings in prenatal diagnostic testing may or may not have clear prognostic significance for the phenotype. We studied experts' opinions of the benefit and disadvantage of an incidental prenatal diagnosis of a sex chromosomal aneuploidy (SCA).

METHODS

We interviewed 16 experts in the field of counseling and treatment of people with SCA and asked 13 clinical geneticists and genetic associates about the clinical relevance of an incidental prenatal diagnosis of SCA.

RESULTS

Most of the experts and clinical geneticists (87.5% and 76.9%, respectively) stated that an incidental prenatal diagnosis of SCA was a benefit for the child and the parents. They acknowledged the possibility of parental decisions to terminate pregnancy. Expert options in screening, training, and treatment of health, behavior, and fertility problems increase with an early diagnosis of SCA.

CONCLUSION

Most experts favored an incidental prenatal diagnosis of SCA despite the complex counseling issues and their acknowledgment of possible parental decisions to terminate pregnancy. They believed the benefits greatly outweigh the disadvantages.

Sex chromosomes and sex chromosome abnormalities

This article focuses on constitutional sex chromosome abnormalities detected by conventional cytogenetics and fluorescence in situ hybridization. The author discusses the two general classifications of abnormalities: numerical and structural. Also included are descriptions of unique aspects of X and Y chromosomes, technological advances in detection, and future perspectives.

Incidental prenatal diagnosis of sex chromosome aneuploidies: health, behavior, and fertility

Objective. To assess the diagnostic relevance of incidental prenatal findings of sex chromosome aneuploidies. Methods. We searched with medical subject headings (MeSHs) and keywords in Medline and the Cochrane Library and systematically screened publications on postnatally diagnosed sex chromosomal aneuploidies from 2006 to 2011 as well as publications on incidentally prenatally diagnosed sex chromosomal aneuploidies from 1980 to 2011. Results. Postnatally diagnosed sex chromosomal aneuploidies demonstrated three clinical relevant domains of abnormality: physical (22-100%), behavior (0-56%), and reproductive health (47-100%), while incidentally prenatally diagnosed sex chromosomal aneuploidies demonstrated, respectively, 0-33%, 0-40%, and 0-36%. Conclusion. In the literature incidental prenatal diagnosis of sex chromosomal aneuploidies is associated with normal to mildly affected phenotypes. This contrasts sharply with those of postnatally diagnosed sex chromosomal aneuploidies and highlights the importance of this ascertainment bias towards the prognostic value of diagnosis of fetal sex chromosomal aneuploidies. This observation should be taken into account, especially when considering excluding the sex chromosomes in invasive prenatal testing using Rapid Aneuploidy Detection.

Long term follow-up of a child with ambiguous genitalia, mixed gonadal dysgenesis, and unusual mosaicism

Mixed gonadal dysgenesis (MGD) is a condition of abnormal and asymmetrical gonadal development. This disorder is typically associated with 45,X/46,XY mosaicism; however, other karyotypes have been rarely reported. The phenotype characterizing MGD is highly variable, although in most cases ambiguous genitalia are found. In addition, many individuals with MGD exhibit stigmata of Turner's syndrome. We describe a patient with MGD, found to have a 45,X/47,XYY karyotype, with the majority of the cell lines being 47,XYY. To our knowledge, our report is the first to describe the long-term follow-up of a patient with ambiguous genitalia diagnosed at birth with 45,X/47,XYY mosaicism.

Trisomy 21 with XYY

A case of double aneuploidy involving chromosome 21 and Y is reported in an eight-month-old infant with developmental delay and failure to thrive. Patient had all classical phenotypical features of trisomy 21 except, absence of epicanthal folds. The diagnosis was confirmed by cytogenetic study performed on peripheral blood leucocyte culture using G-banding. Literature review revealed only 17 cases of XYY and trisomy 21 reported so far. No such case is reported in Indian literature. Relevant literature is reviewed and possible effects of trisomy 21 on XYY and that of XYY on trisomy 21 has been discussed. A routine chromosomal study even in patient with classical features of Down syndrome has been advocated. Interestingly, our patient also had left to right shunts at atrial and ductal level and tricuspid regurgitation. Given the rarity of the disorder and scanty published data the incidence, phenotype and recurrence risk are difficult to establish.

47,XYY karyotype and normal SRY in a patient with a female phenotype

A rare case of a female patient with a 47,XYY karyotype is described. She had normal female external genitalia, bilateral testes, rudimentary Fallopian tubes and no uterus. Molecular analysis revealed a normal SRY encoding sequence. The possible events in the etiology of this sex reversal entity are discussed.

Risk of gonadoblastoma in female patients with Y chromosome abnormalities and dysgenetic gonads

We report two female patients with gonadal dysgenesis and sex chromosome mosaicism involving the Y chromosome. Conventional karyotyping was supplemented with fluorescent in situ hybridisation techniques in order to confirm the presence of Y chromosomes. One patient is a phenotypic female with karyotype 45,X/46,X,idic(Y)(q11.2). She underwent a laparoscopic gonadectomy at which streak ovaries without evidence of gonadoblastoma were removed. The second patient presented as a virilised female with karyotype 45,X/47,XYY. At laparoscopy, she was found to have mixed gonadal dysgenesis with a gonadoblastoma in situ. We recommend early gonadectomy in female children presenting with gonadal dysgenesis and the presence of a Y chromosome although once the gonadoblastoma locus on Y chromosome gene has been cloned it may be possible to identify those patients who have a low risk of developing gonadoblastoma.

Detection of SRY in 45,X/47,XYY mosaicism leading to phenotypic female

SRY on the Y chromosome initiates male sex determination. We tested a phenotypic female with sex chromosome mosaicism, X/XYY, for SRY expression. SRY was determined by polymerase chain reaction (PCR) amplification in genomic DNA from a female patient with a sex chromosome mosaic complement, 45,X/47,XYY, followed by sequencing analyses. The patient yielded the PCR product with predicted size and homology to the consensus sequence of SRY. The demonstration of SRY provides evidence that the female phenotype in the presence of sex chromosome mosaicism, X/XYY, may result from alterations in another part of the sex-determining pathway or downstream from SRY.

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.

Phenotype/karyotype correlations of Y chromosome aneuploidy with emphasis on structural aberrations in postnatally diagnosed cases

Over 600 cases with a Y aneuploidy (other than non-mosaic 47,XYY) were reviewed for phenotype/karyotype correlations. Except for 93 prenatally diagnosed cases of mosaicism 45,X/46,XY (79 cases), 45,X/47,XYY (8 cases), and 45,X/46,XY/47,XYY (6 cases), all other cases were ascertained postnatally. Special emphasis was placed on structural abnormalities. This review includes 11 cases of 46,XYp-; 90 cases of 46,XYq- (52 cases non-mosaic; 38 cases 45,X mosaic); 34 cases of 46,X,r(Y) (9 cases non-mosaic and 25 cases 45,X mosaic); 8 cases of 46,X,i(Yp) (4 non-mosaic and 4 mosaic with 45,X); 12 cases of 46,X,i(Yq) (7 non-mosaic and 5 mosaic); 44 cases of 46,X,idic(Yq); 80 cases of 46,X, idic(Yp) (74 cases had breakpoints at Yq11 and 6 cases had breakpoints at Yq12); 130 cases of Y/autosome translocations (50 cases with a Y/A reciprocal translocation, 20 cases of Y/A translocation in 45,X males, 60 cases of Y/DP or Y/Gp translocations); 52 cases of Y/X translocations [47 cases with der(X); 4 cases with der(Y), and 1 case with 45,X with a der(X)], 7 cases of Y/Y translocations; 151 postnatally diagnosed cases of 45,X/46,XY; 14 postnatally diagnosed cases of 45,X/47,XYY; 18 cases of 45,X/46,XY/47,XYY; and 93 aforementioned prenatally diagnosed cases with a 45,X cell line. It is clear that in the absence of a 45,X cell line, the presence of an entire Yp or a region of it including SRY would lead to a male phenotype in an individual with a Y aneuploidy, whereas the lack of Yp invariably leads to a female phenotype with typical or atypical Ullrich-Turner syndrome (UTS). Once there is a 45,X cell line, regardless of whether there is Yp, Yq, or both Yp and Yq, or even a free Y chromosome in other cell line, there is an increased chance for that individual to be a phenotypic female with UTS manifestations or to have ambiguous external genitalia. This review once again shows a major difference in reported phenotypes between postnatally and prenatally diagnosed cases of 45,X/46,XY, 45,X/47,XYY, and 45,X/46,XY/47,XYY mosaicism. It appears that ascertainment bias can explain the fact that all known patients with postnatal diagnosis are phenotypically abnormal, while over 90% of prenatally diagnosed cases are reported to have a normal male phenotype. Further elucidation of major Y genes and their clinical significance can be expected in the rapidly expanding gene mapping projects. More, consequently better, phenotype/karyotype correlations can be anticipated at both the cytogenetic and the molecular level.