Core Concepts: Chromosome Aneuploidies

Abstract

Aneuploidy, or deviation from the diploid human chromosome complement of 46, may have physical effects ranging from mild or undetectable, as in a male infant with 47 chromosomes including an additional Y chromosome, to severe, as occurs in infants with an additional chromosome 13 or 18. We discuss the autosomal (13, 18, and 21) and sex chromosome (X, Y) aneuploidies that can be expected in the neonatal health care setting, including clinical signs and symptoms that may be indications for further study. We review appropriate diagnostic testing including chromosome, fluorescent in situ hybridization, and microarray comparative genomic hybridization studies, indicating where parental follow-up studies are necessary to provide accurate recurrence risk counseling. For each aneuploid condition that is likely to be encountered in a living infant, we review appropriate clinical management strategies. Suggested readings and family resources are provided for the aneuploidies that are commonly observed in the newborn, and the reader is directed to additional resources for partial aneuploidies, which are beyond the scope of this review.