pediatrics
Chromosomal Deletion Syndromes
Introduction
Chromosomal deletion syndromes result from loss of parts of chromosomes. They may cause severe congenital anomalies and significant intellectual and physical disability. Specific chromosomal deletion syndromes are less likely to be suspected prenatally but may be incidentally discovered at that time if karyotyping is done for other reasons. Postnatal diagnosis is suspected by clinical appearance and is confirmed by karyotyping, if the deletion is relatively large, or by other cytogenetic techniques such as fluorescent in situ hybridization or microarray analysis. (See also Overview of Chromosomal Abnormalities .) Chromosomal deletion syndromes typically involve larger deletions that are usually visible on karyotyping. Syndromes involving smaller deletions (and additions) that affect one or more contiguous genes on a chromosome and are not visible on karyotyping are considered Microdeletion and Microduplication Syndromes . (See also 