A newborn girl is evaluated in the neonatal intensive care unit for difficulty breathing. The patient was born at term via spontaneous vaginal delivery. Since birth, she has had difficulty breathing with loud snoring sounds and intermittent oxygen desaturations. She has been unable to breastfeed due to her breathing problems. Breathing improves significantly when the patient is placed in a prone position. On examination, there is a small mandible, posteriorly displaced tongue, and U-shaped cleft palate. The abnormalities described represent an example of which of the following?

Question

A newborn girl is evaluated in the neonatal intensive care unit for difficulty breathing.  The patient was born at term via spontaneous vaginal delivery.  Since birth, she has had difficulty breathing with loud snoring sounds and intermittent oxygen desaturations.  She has been unable to breastfeed due to her breathing problems.  Breathing improves significantly when the patient is placed in a prone position.  On examination, there is a small mandible, posteriorly displaced tongue, and U-shaped cleft palate.  The abnormalities described represent an example of which of the following?

Quizplus · Accepted Answer

11ec160b_373b_5826_9249_ada9c0215ebf_MD0001_00 This patient has a small mandible, posteriorly displaced tongue, and U-shaped cleft palate, which is consistent with Pierre Robin sequence. A sequence occurs when a single developmental defect causes a cascade of additional malformations. In Pierre Robin sequence, hypoplasia of the mandibular prominence leads to micrognathia. Severe micrognathia causes posterior displacement of the tongue (glossoptosis), which blocks fusion of the palatine shelves, resulting in a cleft palate that is characteristically U-shaped. Difficulty breathing occurs because the tongue prolapses into the posterior oropharynx, blocking airflow. Breathing improves when the patient is in a prone position because gravity pulls the tongue anteriorly, opening the airway. (Choice A) An association is a collection of malformations that are often seen together and do not have a known, common cause (eg, VACTERL association). (Choice B) A disruption occurs when an external insult (rather than a genetic defect) interrupts and arrests normal fetal development (eg, when an amniotic band disrupts limb development). No specific external insult has been linked to Pierre Robin sequence, and most cases result from genetic abnormalities. (Choice C) Genomic imprinting is a normal process that refers to selective activation of gene expression depending on the parent of origin. Aberrant imprinting occurs with uniparental disomy (ie, when a person receives 2 copies of a chromosome from the same parent and no copy from the other parent). Prader-Willi syndrome and Angelman syndrome (15q) are examples of conditions caused by dysfunctional imprinting. (Choice E) A syndrome is a collection of malformations that have a common cause but are not related anatomically. For example, upslanting palpebral fissures, atrioventricular canal defect, and single palmar crease are all due to trisomy 21. Educational objective: Pierre Robin is characterized as a sequence because the primary defect (hypoplasia of the mandibular prominence) leads to a cascade of further malformations (ie, micrognathia, posteriorly displaced tongue, U-shaped cleft palate).

A Newborn Girl Is Evaluated in the Neonatal Intensive Care