A newborn is examined immediately after an induced vaginal delivery for fetal growth retardation. On visual inspection, the infant has low-set ears, a small mandible, and a prominent occiput. The neonate has a weak cry and increased tone of the extremities, including clenched hands with second and fifth digits on top of the third and fourth digits. Cardiac auscultation reveals a harsh, IV/VI holosystolic murmur heard best at the left sternal border. The infant is transferred to the neonatal intensive care unit for further workup and management. Which of the following is the most likely chromosomal abnormality in this infant?

Question

A newborn is examined immediately after an induced vaginal delivery for fetal growth retardation.  On visual inspection, the infant has low-set ears, a small mandible, and a prominent occiput.  The neonate has a weak cry and increased tone of the extremities, including clenched hands with second and fifth digits on top of the third and fourth digits.  Cardiac auscultation reveals a harsh, IV/VI holosystolic murmur heard best at the left sternal border.  The infant is transferred to the neonatal intensive care unit for further workup and management.  Which of the following is the most likely chromosomal abnormality in this infant?

Quizplus · Accepted Answer

11ec160b_3781_887e_9249_8b353f812fc5_MD0001_00 This patient has trisomy 18 (Edwards syndrome), in which a complete extra copy of chromosome 18 is inherited as a result of meiotic nondisjunction. This error in oocyte division occurs prior to ovulation and fertilization and increases with maternal age >35. Dysmorphic features include micrognathia, low-set ears, prominent occiput, and rocker bottom feet. Patients have significant hypertonia, including clenched hands with overlapping fingers. Anomalies of cardiac (eg, ventricular septal defect, patent ductus arteriosus), genitourinary (eg, horseshoe kidney), and gastrointestinal (eg, Meckel's diverticulum, malrotation) systems are characteristic. Prenatal ultrasound findings include fetal growth restriction, as seen in this patient. The majority of those affected die in utero; half of livebirths die by age 2 weeks. Surviving patients have severe intellectual disability. (Choice A) Cri-du-chat syndrome (5p deletion) presents with a weak or "cat-like" cry as well as hypotonia, failure to thrive, and developmental delay. Phenotypic features include microcephaly, low-set ears, hypertelorism, and a broad nasal bridge. (Choice B) Features of DiGeorge syndrome (22q11 deletion) include aortic arch anomalies, thymic hypoplasia/aplasia, and hypocalcemia (parathyroid gland underdevelopment). Phenotypically, neonates can present with hypertelorism, low-set ears, micrognathia, and cleft palate. (Choice C) Trisomy 13 (Patau syndrome) presents with midline facial defects (eg, holoprosencephaly, cleft lip/palate), musculoskeletal abnormalities (eg, polydactyly), and gastrointestinal anomalies (eg, omphalocele, umbilical hernia). Trisomy 13 is notably not associated with overlapping fingers. (Choice E) Trisomy 21 (Down syndrome) is the most common autosomal trisomy. Classic findings include a flat facial profile, upslanting palpebral fissures, low-set small ears, single transverse palmar crease, and hypotonia. Educational objective: Trisomy 18, or Edwards syndrome, is most commonly the result of meiotic nondisjunction due to advanced maternal age. Key findings include fetal growth retardation, hypertonia (clenched hands with overlapping fingers), rocker bottom feet, and cardiac/gastrointestinal/renal defects. __________ References: The trisomy 18 syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/23088440)

A Newborn Is Examined Immediately After an Induced Vaginal Delivery