Question 103

Question:

An infant is noted to have epicanthal folds, a broad nasal bridge, a large tongue, small ears, hypertelorism, Brushfield spots, a single palmar crease on each hand, and a harsh holosystolic murmur. What is the most common cause of this syndrome?

Correct Answer: B.  Maternal meiotic nondisjunction

This infant has Down syndrome. Trisomy 21 is most commonly caused by maternal meiosis I nondisjunction (the incidence increases with advanced maternal age). Patients with Down syndrome have an increased incidence of congenital heart disease. Hypertelorism refers to wide-spaced eyes. Brushfield spots are small spots at the periphery of the iris formed by abnormal connective tissue aggregation. Triploidy usually results in spontaneous abortion. Deletion in the short arm of chromosome 5 leads to Cri-du-chat syndrome.