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Genetics and metabolic disorders
Published in Jagdish M. Gupta, John Beveridge, MCQs in Paediatrics, 2020
Jagdish M. Gupta, John Beveridge
The karyotype in A is a balanced Robertsonian translocation. Only 45 chromosomes are present but as the translocation chromosome contains all the functional portions of both chromosome 13 and 14, there is no loss of functional chromosomal material. Individuals with 47,XXY and 47,XYY frequently remain undiagnosed throughout life as the features are often mild. Turner syndrome girls are short but the majority pass easily as normal individuals in society. The majority of individuals with conditions C, D and E show no obvious intellectual deficit.
Aicardi Syndrome and Klinefelter Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Klinefelter syndrome (Klinefelter's syndrome, XXY syndrome, or XXY trisomy) is due to the presence of one extra copy of the X chromosome in each cell (47,XXY), which escapes X-inactivation or displays polymorphisms in specific genes (e.g., the trinucleotide repeat length of androgen receptor gene), leading to subdued gonadal development, reduced levels of testosterone, and altered brain development and growth. Based on microarray gene expression analysis of lymphocytes and testis transcriptome analysis of Sertoli, Leydig, and germ cells from Klinefelter syndrome males, 480 autosomal genes are upregulated and >200 genes are downregulated. Epigenetic modulation of autosomal genes (e.g., sperm-associated antigen 1 [SPAG1] on the long arm of chromosome 8 that codes for a protein involved in signal transduction pathways in spermatogenesis) caused by aneuploidy may appear in a tissue-specific manner, manifesting as gonadal failure, insulin resistance, dyslipidemia, and coagulability and other symptoms. Due to the effects of extra genetic material, Klinefelter syndrome males with 48,XXXY or 49,XXXXY karyotype often show more severe signs and symptoms than those with classic 47,XXY karyotype. Apart from altered male sexual development, these variants are associated with congenital anomalies (e.g., inguinal hernia, congenital heart disease, cleft palate and velopharyngeal insufficiency, and kidney malformation), intellectual disability, distinctive facial features, skeletal abnormalities, poor coordination, severe speech problems, and dental conditions (e.g., taurodontism and caries) [3].
The Genetics of Spontaneous Abortions
Published in Howard J.A. Carp, Recurrent Pregnancy Loss, 2020
47,XXY and 47,XYY each occur in about 1 per 800 live-born male births. 47,XXX occurs in 1 per 800 female births. X or Y polysomies are only slightly (10%) more common in abortuses than in live borns [55]. Thus, there is little additional lethality, and that occurring probably is due to increased anomalies (e.g., cardiac).
When to Disclose a Borderline Incidental Finding
Published in The American Journal of Bioethics, 2022
Susanna McGrew, Benjamin E. Berkman
The case summary also notes that individuals with Klinefelter’s syndrome may seek assisted reproductive technologies for sperm harvesting. Most individuals are azoospermic, although mosaic individuals (i.e., those who have both XY and XXY chromosomes) present with reduced concentrations of sperm and thus less severe infertility (Hawksworth et al. 2018). Even with comprehensive insurance, however, those technologies can be expensive, and they are more likely to be effective closer to puberty. Mr. Robinson, at age 25, will soon be beyond the window of opportunity for sperm harvesting. It is worth noting that men with sickle cell disease also have lower baseline fertility than the general population, so Mr. Robinson’s likelihood of success with assisted reproductive technologies may be even lower than that of other individuals with Klinefelter’s syndrome (Mishkin et al. 2020). We don’t want to exaggerate the potential fertility benefits of assisted reproductive technology, but even if such technologies are not successful, it may be helpful for Mr. Robinson to learn about fertility challenges.
To Disclose or Not to Disclose: Secondary Findings of XXY Chromosomes
Published in The American Journal of Bioethics, 2022
Benjamin S. Wilfond, Devan M. Duenas, Liza-Marie Johnson
Mr. Robinson was 25 years old when he enrolled in a study to investigate the role of the environment and the microbiome in the phenotypic expression of sickle cell disease. His participation consisted of a single visit during which he provided blood and saliva samples. The informed consent form stated that if incidental clinical findings were discovered, they might be disclosed if “urgently important to a participant’s health.” Genomic sequencing of his samples performed two years later in a non-CLIA research laboratory indicated the presence of XXY chromosomes, also known as Klinefelter’s syndrome. The research team does not know if Mr. Robinson has previously received a diagnosis of Klinefelter’s syndrome. He continues to be followed in the hematology clinic for his sickle cell disease.
Noninvasive prenatal screening in southeast China: clinical application and accuracy evaluation
Published in Expert Review of Molecular Diagnostics, 2022
Li Wen, Jiye Gao, Leilei Huang, Dongmei Li, Guansheng Zhong
Though there was no significant association between Z-score of NIPS suggested positive cases and true positive results in SCA using logistic regression analysis, ROC curve analysis showed the relatively satisfied AUC for SCA separately (Table 5). The optimal cutoff values were −4.858, 36.527, 23.669 and 70.346 for 45,X, 47,XXX, 47,XXY, and 47,XYY, respectively. Moreover, the sensitivity was high (45,X: 84.21%; 47,XXX: 100%; 47,XXY: 93.18%; 47,XYY: 100%) while the specificity was low (45,X: 48.15%; 47,XXX: 85.71%; 47,XXY: 40.00%; 47,XYY: 60.00%). According to the optimal cutoff of Z-score, NIPS-positive cases of SCA were divided into three groups: the intermediate risk group (3 ≤ Z-score < cutoff or cutoff < Z-score < −3), the high-risk group (Z score ≥ cutoff or Z score ≤ cutoff) and all risk group (Z-score ≥ 3). As shown in Table 5, significant differences of PPV between intermediate risk group and high-risk group were expressed in 45,X, 47,XXX, and 47,XYY. Nevertheless, no difference was found in 47,XXY between groups. Surprisingly, there seemed to be a higher PPV along with the higher Z-score except for 47,XXX.