An infant born to a 26-year-old woman is evaluated shortly after delivery. Birth weight and length are at the 10th and 15th percentiles, respectively. Vital signs are normal. Physical examination shows a protruding tongue, excessive skin at the nape of the neck, and upslanting palpebral fissures. The startle reflex is symmetric and weak. Cardiac auscultation reveals a harsh, III/VI systolic murmur heard best over the lower left sternal border. The patient has normal external female genitalia. Review of maternal medical records shows a past history of 2 spontaneous abortions in the last 3 years. Echocardiography confirms the presence of a ventricular septal defect. Which of the following karyotypes is most likely to be found in this infant?

Question

An infant born to a 26-year-old woman is evaluated shortly after delivery.  Birth weight and length are at the 10th and 15th percentiles, respectively.  Vital signs are normal.  Physical examination shows a protruding tongue, excessive skin at the nape of the neck, and upslanting palpebral fissures.  The startle reflex is symmetric and weak.  Cardiac auscultation reveals a harsh, III/VI systolic murmur heard best over the lower left sternal border.  The patient has normal external female genitalia.  Review of maternal medical records shows a past history of 2 spontaneous abortions in the last 3 years.  Echocardiography confirms the presence of a ventricular septal defect.  Which of the following karyotypes is most likely to be found in this infant?

Quizplus · Accepted Answer

Eductional Objective: Unbalanced Robertsonian translocations account for a minority of Down syndrome cases.  Karyotyping shows 46 chromosomes with a translocation between 2 acrocentric nonhomologous chromosomes [eg, 46, XX, t(14;21)].

An Infant Born to a 26-Year-Old Woman Is Evaluated Shortly