Prenatal Genetic Diagnosis and Origin Analysis of Rare Complete Translocation Trisomy 18 / 中山大学学报(医学科学版)

ObjectiveTo discuss the origin of rare abnormal karyotypes of fetuses with high risk of trisomy 18 revealed by non-invasive prenatal testing （NIPT） and its impact on fertility. MethodsThe cytogenetic and molecular genetic analyses were performed on the abnormal chromosomes of a prenatally diagnosed fetus with rare complete translocation trisomy 18. Using the keywords “translocation trisomy 18” or “trisomy 18 translocation” in both Chinese and English， we searched PubMed， CNKI， SinoMed， WanFang Data， CQ VIP and the Chinese Medicine database. The relevant case series were retrieved and critically appraised. ResultsG-banded karyotype analysis showed that the maternal karyotype was 46，XX，t（9；18）（q31.2；q23） and the fetal karyotype was 47， XN， t （9； 18） （q31.2；q23）mat， +18， which was a rare complete translocation type of trisomy 18. The SNP array revealed the fetus had increased copy number of chromosome 18 and two complete chromosome 18 inherited from the mother with balanced chromosomal translocation. Literature search found two children with complete translocation trisomy 18 reported abroad. Both of them had trisomy 18 phenotype and originated from the balanced translocation between parental chromosome 18 and other chromosomes. ConclusionNIPT gives an effective advance warning of trisomy 18. SNP array not only improves the detection rate of chromosomal abnormalities， but also helps identify the origin. The karyotype is still the gold standard for prenatal diagnosis.

Cytogenetic Analysis Of Down Syndrome

Objective: Down syndrome is a common genetic disease, diagnosed with congenital malformation/mental retardation. Down syndrome occurs in all races & economic levels. It is caused by third copy of chromosome 21, there are there forms of DS. Simple Trisomy 21, Translocation Trisomy and Mosaic Trisomy. The aim of the study is to know cause of Down syndrome. Chromosomal analysis was carried out by G banding technique. Materials and Methods: 1 ml of peripheral blood samples were collected in Out Patient Department of pediatrics and Cytogenetic analysis was per-formed. Results: Out of 28, 3 female cases, 2 male cases were Down syndrome, All the 5 cases were free trisomy 21, which is common type of Down syndrome; we have not identified Robertsonian translocation and mosaic type of DS. Conclusion: The present analysis shows that genetic risk factors are responsible for the incidence of Down syndrome.

Prevalence of Down Syndrome in Western India: A Cytogenetic Study.

Aim: To study the prevalence of Down syndrome by conventional chromosome analysis and Gbanded karyotyping. Materials and Methods: A retrospective analysis was performed on the case records of2750 paediatrics patients, of which 682 cases of confirmed Down syndrome was recorded by G-banding karyotyping. Results: Non-disjunction was the most common type of abnormality followed by Robertsonian translocation and lastly mosaic in ratio of 92.2:7.0:0.73 respectively. Conclusion: Results suggest that advanced maternal age is classic risk factor attributed to the incidences of Down syndrome.

Chimeric Fusion Karyotypes in Childhood B-cell Acute Lymphoblastic Leukemia.

Cytogenetics study using combination of conventional cytogenetics and fluorescent insitu hybridization was carried out in 171 pediatric acute lymphoblastic leukemia patients subgrouped to B-ALL (n=126) and T-ALL (n=45) by bone marrow morphology and immunophenotype. The chromosomal aberration frequency in B-ALL and T-ALL was 79% and 71%, respectively. TEL/AML1 translocation was detected in 28% of patients.