A 33-year old primigravida comes to the office to discuss results of prenatal testing. The patient is at 12 weeks gestation based on her last menstrual period. She has been taking prenatal vitamins inconsistently due to pregnancy-related nausea. Maternal alpha-fetoprotein level is reduced, and an ultrasound reveals increased nuchal translucency. Chorionic villous sampling shows a fetal karyotype of 47, XX, +21. The fetus is at greatest risk of developing which of the following conditions?

Question

A 33-year old primigravida comes to the office to discuss results of prenatal testing.  The patient is at 12 weeks gestation based on her last menstrual period.  She has been taking prenatal vitamins inconsistently due to pregnancy-related nausea.  Maternal alpha-fetoprotein level is reduced, and an ultrasound reveals increased nuchal translucency.  Chorionic villous sampling shows a fetal karyotype of 47, XX, +21.  The fetus is at greatest risk of developing which of the following conditions?

Quizplus · Accepted Answer

11ec160b_3780_770c_9249_0fa291587edf_MD0001_00 Down syndrome (trisomy 21) is the most common trisomy in liveborn infants. The diagnosis is often suspected by prenatal screening (eg, decreased maternal serum alpha-fetoprotein [AFP]) and/or ultrasonography (eg, increased nuchal translucency) and confirmed by chorionic villous sampling or amniocentesis. Most cases are caused by meiotic nondisjunction due to maternal age >35, which result in 3 complete copies of chromosome 21. Duodenal atresia, the failure of recanalization of the duodenum in early gestation, is the most common gastrointestinal abnormality associated with Down syndrome. Infants present during the first few days of life with bilious emesis and the classic "double-bubble" sign, which represents the dilated stomach and proximal duodenum. Patients with Down syndrome are also at risk for imperforate anus, Hirschsprung disease, tracheoesophageal fistula, and celiac disease. (Choice B) Holoprosencephaly, a severe developmental defect of the forebrain (prosencephalon), is associated with trisomy 13 (Patau syndrome). Additional features include microcephaly, microphthalmia, cleft lip/palate, and intellectual disability. (Choices C and E) Markedly elevated AFP levels are associated with open neural tube and ventral wall defects (omphalocele, gastroschisis). Myelomeningocele is associated with trisomy 18, and omphalocele is associated with trisomies 13 and 18. (Choice D) Nephroblastoma, or Wilms tumor, typically presents before age 5 with an abdominal mass. The majority of cases are sporadic, but a subset is associated with Beckwith-Wiedemann syndrome. (Choice F) Pyloric stenosis is caused by hypertrophy of the pylorus and presents at age 3-6 weeks with forceful, nonbilious emesis. Pyloric stenosis is not associated with Down syndrome. Educational objective: Down syndrome (trisomy 21) is associated with decreased maternal serum alpha-fetoprotein and increased nuchal translucency. Duodenal atresia is the most common gastrointestinal complication in these patients. __________ References: Associated congenital anomalies among cases with Down syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/26578241)

A 33-Year Old Primigravida Comes to the Office to Discuss