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→Clinical Summary
This 44-year-old woman was 12 weeks pregnant with her third child when routine blood work showed a maternal serum alpha-fetoprotein level that was lower than expected for her stage of pregnancy. At 15-weeks of gestation she underwent ultrasound-guided amniocentesis and samples of the fluid containing cells were smeared onto glass slides for fluorescent in situ hybridization (FISH). The remainder of the sample was spun down and the fluid was sent for analysis and the cells were cultured for karyotyping.
== Images ==
File:IPLab5Downs6.jpg|This is a karyotype of a patient with Turner syndrome (45, X).
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== Study Questions ==
* <spoiler text="Why are alpha-fetoprotein levels tested in maternal serum? What is the significance of a low alpha-fetoprotein level?">Increased or decreased alpha-fetoprotein levels are indicative of neural tube defects or Down syndrome, respectively. A low alpha-fetoprotein level along with low unconjugated estriol and elevated hCG suggest an increased risk for Down syndrome. Further testing is warranted.</spoiler>
* <spoiler text="What is the most common cause of trisomy?">Meiotic nondisjunction.</spoiler>
* <spoiler text="What are some common physical/clinical abnormalities seen in Down syndrome?">Epicanthic folds and flat facial profile, low set ears, simian crease, congenital heart defects, intestinal stenosis, umbilical hernia, hypotonia, predisposition to leukemia.</spoiler>
== Additional Resources ==
=== Reference ===
* [http://emedicine.medscape.com/article/943216-overview eMedicine Medical Library: Down Syndrome]
* [http://emedicine.medscape.com/article/945649-overview eMedicine Medical Library: Klinefelter Syndrome]
* [http://emedicine.medscape.com/article/949681-overview eMedicine Medical Library: Turner Syndrome]
* [http://www.merckmanuals.com/professional/pediatrics/chromosomal_anomalies/overview_of_chromosomal_anomalies.html Merck Manual: Chromosomal Abnormalities]
=== Journal Articles ===
* Garcia-Heras J, Rao PN. [http://www.ncbi.nlm.nih.gov/pubmed/10334476 A brief review of cryptic duplications of 21q as an emerging cause of Down syndrome: practical considerations for accurate detection]. ''Clin Genet'' 1999 Mar;55(3):207-11.
=== Images ===
* [{{SERVER}}/library/index.php?/tags/788-downs_syndrome PEIR Digital Library: Down Syndrome Images]
* [{{SERVER}}/library/index.php?/category/143 PEIR Digital Library: Genetics Images]
* [http://library.med.utah.edu/WebPath/PEDHTML/PEDIDX.html WebPath: Pediatric-Perinatal Pathology]
{{IPLab 5}}
[[Category: IPLab:Lab 5]]