Review Question - QID 106989

This patient's karyotype is consistent with Turner syndrome, which is associated with a webbed neck.

Turner syndrome is the most common cause of monosomy (45,XO) and typically results from nondisjunction during meiosis I. Turner syndrome may be uniformly present in a patient's cells, or may present as mosaicism. Mosaicism in this condition results from non-disjunction that occurs during a portion of embryological cells during development. In addition, Turner syndrome may result from a partially, rather than fully, deleted X-chromosome.

Morgan reviews Turner syndrome and notes that its incidence is between 1:2,500-3,000 live female births. Physical exam often shows a webbed neck, broad chest, cubitus valgus (forearm malformation), and misshapen ears. These patients have normal intelligence, unlike other chromosomal abnormality syndromes, but they may have problems with "nonverbal, social, and psychomotor skills." Like other chromosomal abnormalities, these patients are at increased risk of congenital heart defects. They are also at increased risk for other abnormalities, such as osteoporosis, renal malformations (horseshoe kidney), lymphedema, diabetes, and sensorineural hearing loss.

Sybert and McCauley review Turner syndrome and discuss its management. Patients can be treated with recombinant human growth hormone (hGH), which may lead to an increase in height between 0-12 cm, depending on when treatment is begun. Hormone replacement therapy is typically begun around the age of 14 to allow for proper puberty development and to prevent the early development of osteoporosis.

Figure A and Illustration A demonstrates the karyotype of a person with Turner syndrome. The red box demonstrates the absence of a sex chromosome. Illustration B demonstrates a normal karyotype. The second sex chromosome can be either an X or Y. If it is an X, it is a female's karyotype, or if it is a Y, it is a male's. Illustration C demonstrates the webbed neck of Turner syndrome.

Incorrect answers:
Answer 1: Gynecomastia can be seen with patients who have Klinefelter syndrome (47,XXY).

Answer 2: Rocker-bottom feet can be seen with patients who have Edward's syndrome (trisomy 18).

Answer 3: Elfin facies are characteristic of patients who have William's syndrome (microdeletion of the long arm of chromosome 7).

Answer 5: Microcephaly can see be in patients with Patau's syndrome (trisomy 13).