A newborn girl is evaluated in the nursery after an uncomplicated spontaneous vaginal delivery to a 29-year-old primigravida. The mother declined prenatal testing and ultrasound examination during the pregnancy. Her pregnancy was otherwise uneventful, and she took prenatal vitamins throughout. Examination of the neonate shows a posterior neck mass and bilateral nonpitting edema of the hands and feet. Femoral pulses are diminished. Neck ultrasound reveals a mass composed of cystic spaces separated by connective tissue. Which of the following is the most likely underlying mechanism responsible for this patient's condition?

Question

A newborn girl is evaluated in the nursery after an uncomplicated spontaneous vaginal delivery to a 29-year-old primigravida.  The mother declined prenatal testing and ultrasound examination during the pregnancy.  Her pregnancy was otherwise uneventful, and she took prenatal vitamins throughout.  Examination of the neonate shows a posterior neck mass and bilateral nonpitting edema of the hands and feet.  Femoral pulses are diminished.  Neck ultrasound reveals a mass composed of cystic spaces separated by connective tissue.  Which of the following is the most likely underlying mechanism responsible for this patient's condition?

Quizplus · Accepted Answer

11ec160b_375a_a036_9249_d39fe9bc2cea_MD0001_00 This patient's posterior neck mass is most likely a cystic hygroma, and the bilateral extremity swelling is consistent with lymphedema. These findings in the context of diminished femoral pulses (suggestive of coarctation of the aorta) in a newborn girl are classic for Turner syndrome. Turner syndrome is characterized by a 45,X karyotype due to loss of paternal chromosome X. Both cystic hygromas and lymphedema occur due to abnormalities of lymphatic outflow in Turner syndrome. The swelling decreases with age. (Choice A) In congenital adrenal hyperplasia (adrenogenital syndrome), patients have abnormal sexual differentiation due to defective hormone synthesis in the adrenal glands. The most common enzymatic defect is 21-hydroxylase deficiency. At birth, patients have ambiguous genitalia (girls only) and salt wasting (hypotension, hyponatremia). (Choice B) Androgen insensitivity syndrome results from a defect in testosterone receptors. The typical presentation is a 46,XY adolescent who appears phenotypically female but has primary amenorrhea due to the absence of an internal female reproductive tract and the presence of cryptorchid testes. (Choice D) Trisomy 18 (Edward syndrome) is usually caused by meiotic nondisjunction. These patients have multiple anomalies, including cardiac defects, clenched fists, rocker bottom feet, omphalocele, and low-set ears. (Choice E) Cri du chat is most commonly due to a de novo partial deletion of the short arm of chromosome 5 (5p-). Patients with cri du chat syndrome typically have a round face, catlike cry, and microcephaly. (Choice F) Down syndrome (DS) results from meiotic nondisjunction or Robertsonian translocation involving fetal chromosome 21. These patients have a flat face, oblique palpebral fissures, and epicanthal folds. Atrioventricular defects are the most common cardiac anomaly. Although cystic hygromas can occur in patients with DS, the absence of the dysmorphic features of DS makes this diagnosis unlikely. Educational objective: Turner syndrome (45,X) manifests in the neonate with lymphedema and cystic hygromas. Short stature, primary amenorrhea, and aortic anomalies are the other important clinical features. __________ References: Turner syndrome: diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/17708142) Aortic valve disease in Turner syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/18466808)

A Newborn Girl Is Evaluated in the Nursery After an Uncomplicated