The clinical analysis of small supernumerary marker chromosomes in 17 children with mos 45,X/46,X,+mar karyotype

Clinical characteristics and management of Turner patients with a small supernumerary marker chromosome

OBJECTIVE

To summarize the clinical characteristics of Turner syndrome (TS) with a small supernumerary marker chromosome (sSMC) and discuss the clinical significance and management of TS patients with sSMC.

METHODS

A retrospective analysis was conducted on the clinical data of 244 patients with disorders of sexual development admitted to Peking Union Medical College Hospital from February 1984 to July 2020.

RESULTS

Among the 244 patients with a disorder of sexual development, 69 cases of TS were identified in which 13 patients had sSMC. Their ages ranged from 3 to 28 years old with an average of 14.31 ± 6.40 years. All 13 sSMC-positive patients had typical clinical manifestations of TS except ambiguous genitalia in four cases. SRY gene testing was performed in 11sSMC-positive patients and 10 patients were positive for SRY and one was negative. Among the 10 SRY-positive patients, two cases had hirsutism and clitoral enlargement and two cases had clitoral enlargement only. Nine sSMC and SRY-positive patients underwent gonadectomy and one had left gonadal gonadoblastoma with seminoma in situ and right gonadal seminoma in situ.

CONCLUSIONS

Although the sSMC positive detection rate in DSD patients is uncommon (5.33% in our sample), the positive SRY detection rate in sSMC-positive TS patients was extremely high in our TS patients. And TS patients with sSMC and SRY positive had a significantly increased risk of gonadal germ cell tumors. Routine SRY screening should be performed in TS patients with sSMC, and a gonadectomy should be performed in TS patients with sSMC and SRY positive to prevent the occurrence of tumors.

Prenatal diagnosis and molecular cytogenetic identification of small supernumerary marker chromosomes: analysis of three prenatal cases using chromosome microarray analysis

Small supernumerary marker chromosomes cannot be accurately identified by G-banding, and the related phenotypes vary greatly. It is essential to specify the origin, size, and gene content of marker chromosomes using molecular cytogenetic techniques. Herein, three fetuses with de novo marker chromosomes were initially identified by G-banding. Single nucleotide polymorphism array and fluorescence in situ hybridization were performed to characterize the origins of the marker chromosomes. The karyotypes of the three fetuses were 47,XY,+mar, 46,X,+mar[32]/45,X[68], and 45,X[62]/46,X,+mar[9]. In case 1, the karyotype was confirmed as 47,XY,+ idic(22)(q11.2). Therefore, the sSMC originated from chromosome 22 and was associated with cat eye syndrome. In case 2, the marker chromosome derived from ring chromosome X, and the karyotype was interpreted as 45,X[68]/46,X,+r(X)(p11.1q21.31)[32]. Meanwhile, the karyotype of case 3 was defined as 45,X[62]/46,X,idic(Y)(q11.2) and the marker chromosome originated from chromosome Y. Case 1 continued the pregnancy, whereas the other two pregnancies underwent elective termination. The detailed characterization of marker chromosomes can facilitate informed decision making, prevent uncertainty, and provide proper prognostic assessments. Our findings emphasize the importance for combining cytogenetic and molecular genetic techniques in marker chromosome characterization.

Molecular cytogenetic characterization of small supernumerary marker 15 in infertile male: A case report

Small supernumerary marker chromosomes (sSMCs) are defined as structurally abnormal chromosomes that may be detected pre- or postnataly in patients with developmental and/or mental retardation or infertility. sSMC on chromosome 15 accounts for the highest proportion of all sSMCs and may be detected in subfertile individuals. The present study reports the case of a male patient with oligoasthenoteratozoospermia and an sSMC. The sSMC was identified and characterized according to G-banding analysis, chromosomal microarray analysis (CMA) and fluorescence in situ hybridization (FISH) analysis. Chromosomal karyotype analysis suggested that the patient presented with 47,XY,+mar. CMA was used to characterize the sSMC, which revealed a 0.44-Mb microduplication in 6q25.3q26. Subsequently, FISH using centromere-specific probes for chromosomes 13/21, 14/22 and 15 was applied to identify the origin of the sSMC, which was finally determined to be inverted duplicated(15)(q11.2). It was hypothesized that heterochromatin in the sSMC is responsible for the patient's fertility problem. The presence of heterochromatin may disrupt regular meiosis, thereby affecting normal spermatogenesis. Impaired spermatogenesis in infertile males with an sSMC derived from chromosome 15 was also reviewed by searching published literature and the sSMC database (http://ssmc-tl.com/sSMC.html). For patients with low sperm parameters and complete absence of spermatozoa in the ejaculate, including infertile males with an sSMC with spermatozoa, intracytoplasmic sperm injection is considered as an effective assisted reproductive technique. It may be concluded that molecular cytogenetic techniques are critical tools for delineating sSMCs in infertile males and may be beneficial in identifying sSMC carriers to ensure they receive clinical genetic counseling.

Molecular cytogenetic identification of small supernumerary marker chromosomes using chromosome microarray analysis

Background

This study aimed to evaluate the feasibility of chromosomal microarray analysis (CMA) in detecting the origin and structure of small supernumerary marker chromosomes (sSMCs) in prenatal and postnatal cases and to clarify sSMC-related genotype-phenotype correlations.

Results

Thirty-three cases carrying sSMCs were identified by banding cytogenetics. Of these cases, twenty-nine were first characterized by CMA and only two by FISH. The remaining two cases were excluded for their refusal to accept further examination. The chromosomal origins of twenty-two cases were successfully identified, in which pathogenetic copy number variations (PCNVs) were found in sixteen cases, four cases showed variants of uncertain significance (VOUS), one case showed benign CNVs, and one case showed probable PCNVs. For the nine cases with negative CMA results, only one of them contained centromere heterochromatin likely due to its normal phenotype, whereas reasons for the remaining eight cases were uncertain. We also found that CMA results indicating pathogenic abnormalities further affect the rate of pregnancy termination.

Conclusions

This study showed that CMA combined with cytogenetic analysis is particularly effective in identifying sSMCs. However, in order to establish sSMC-related genotype-phenotype correlations, the inclusion of more sSMC cases will be necessary in future studies.

X-derived marker chromosome in patient with mosaic Turner syndrome and Dandy-Walker syndrome: a case report

Background

Small supernumerary marker chromosomes can be derived from autosomes and sex chromosomes and can accompany chromosome pathologies, such as Turner syndrome.

Case presentation

Here, we present a case report of a patient with mosaic Turner syndrome and Dandy-Walker syndrome carrying a marker chromosome. We showed the presence of the marker chromosome in 33.8% of blood cells. FISH of the probe derived from the marker chromosome by microdissection revealed that it originated from the centromeric region of chromosome X. Additionally, we showed no telomeric sequences and no XIST sequence in the marker chromosome. This is the first report of these two syndromes accompanied by the presence of a marker chromosome.

Conclusion

Marker chromosome was X-derived and originated from centromeric region. Patient has mild symptoms but there is no XIST gene in marker chromosome.

Trial registration

CPG137. Registered 03 March 2017.