An 18-hour-old girl is undergoing a routine examination in the newborn nursery. The patient has urinated 4 times and passed meconium. She was born via uncomplicated vaginal delivery at 41 weeks to a 23-year-old primipara. Apgar scores were 8 and 9 at 1 and 5 minutes, respectively. Birth weight and length are at the 25th percentile for gestation. Temperature is 37.2 C (99 F). The patient is initially asleep but easily roused. Examination shows open and soft fontanelles, posteriorly rotated ears, and a small maxilla. The soft palate has a high arch, but no submucosal cleft is felt on palpation. The neck is short and webbed, without masses. Auscultation reveals a regular heart rate and rhythm with no murmurs. There is good air entry in all fields with no grunting, retractions, or nasal flaring. External genitalia are normal. The hands and feet are moderately edematous. Crease lines on both hands are normal. Pulses are 2+ in all extremities. The mother is concerned about the recurrence risk of this condition in subsequent pregnancies. Which of the following is the best response?

Question

An 18-hour-old girl is undergoing a routine examination in the newborn nursery.  The patient has urinated 4 times and passed meconium.  She was born via uncomplicated vaginal delivery at 41 weeks to a 23-year-old primipara.  Apgar scores were 8 and 9 at 1 and 5 minutes, respectively.  Birth weight and length are at the 25th percentile for gestation.  Temperature is 37.2 C (99 F).  The patient is initially asleep but easily roused.  Examination shows open and soft fontanelles, posteriorly rotated ears, and a small maxilla.  The soft palate has a high arch, but no submucosal cleft is felt on palpation.  The neck is short and webbed, without masses.  Auscultation reveals a regular heart rate and rhythm with no murmurs.  There is good air entry in all fields with no grunting, retractions, or nasal flaring.  External genitalia are normal.  The hands and feet are moderately edematous.  Crease lines on both hands are normal.  Pulses are 2+ in all extremities. The mother is concerned about the recurrence risk of this condition in subsequent pregnancies.  Which of the following is the best response?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfe4_4042_8f63_9990a1c8cb8f_MD0005_00 Turner syndrome occurs in approximately 1 in 2,500 live female births due to a complete or partial loss of an X chromosome. The majority of cases are caused by a random error in cell division, known as nondisjunction. If sex chromosomes fail to separate during egg or sperm formation, one gamete will lack an X chromosome, and fertilization will result in a 45,X zygote (monosomy X). Nondisjunction later during fetal development can result in 45,X mosaicism. Turner syndrome is considered a sporadic event, so the likelihood of recurrence in subsequent pregnancies is similar to that of the general population. nondisjunction (Choices A and D) The recurrence risk is approximately 50% in autosomal dominant disorders in which one parent has the disorder and 25% in autosomal recessive disorders in which both parents are carriers. Because Turner syndrome is not inherited, the recurrence risk for this mother is the same as in the general population. (Choice C) A mother who is a carrier of a chromosome 21 Robertsonian translocation has about a 10% risk of having a child with Down syndrome. Robertsonian translocations, which occur when the long arms of 2 chromosomes fuse, do not typically involve X chromosomes. (Choice E) The risk of nondisjunction resulting in trisomy 21 or Klinefelter syndrome (XXY) increases with maternal age; however, advanced maternal age is not a risk factor for Turner syndrome as the paternal X chromosome is missing in most cases. Educational objective: Turner syndrome is typically due to a random error in cell division, resulting in loss of an X chromosome. No increased recurrence risk is present after giving birth to an infant with Turner syndrome, and unlike other chromosomal nondisjunctions, the risk of 45,X does not increase with maternal age. References: Genetic considerations in the patient with Turner syndrome-45,X with or without mosaicism. (http://www.ncbi.nlm.nih.gov/pubmed/23020909)

An 18-Hour-Old Girl Is Undergoing a Routine Examination in the Newborn