Chromosomal Disorders Practice Test

A 1-month-old infant has a high-pitched cry, microcephaly, and hypotonia. Karyotype shows 46,XY,del(5)(p15). The parents ask what type of chromosomal change this represents compared with trisomy 21. Which statement best explains the difference?

A 1-week-old male newborn has hypotonia and mild respiratory distress. He was born at 37 weeks to a 36-year-old mother. Physical exam shows upslanting palpebral fissures, epicanthal folds, flat nasal bridge, and a single palmar crease. Cardiac exam reveals a harsh holosystolic murmur. Echocardiogram shows an atrioventricular septal defect. CBC shows WBC 28.0 $×10^3$/µL with circulating blasts; hemoglobin 16.8 g/dL; platelets 95 $×10^3$/µL. Karyotype confirms trisomy 21 (47,XY,+21). The neonatologist explains the most likely hematologic complication associated with this chromosomal disorder.