CATCH 22: deletion of locus 22q11 in velocardiofacial syndrome, DiGeorge anomaly, and nonsyndromic conotruncal defects.

DiGeorge anomaly (DGA) and velocardiofacial syndrome (VCFS) are frequently associated with monosomy of chromosomal subband 22q11. It is not clear whether individuals who present with only some of the features (e.g., isolated hypoparathyroidism or conotruncal defects) of these conditions also have the same deletion. In a prospective study of 30 children from 1994 to 1996, we used both high-resolution banding and fluorescence in situ hybridization (FISH) to assess the deletion status of children with a wide range of DGA-like or VCFS-like clinical features. Microdeletion of the chromosomal subband 22q11.22 was detected in 17 children by high-resolution banding and in two additional children with conotruncal defect (CTD) who had submicroscopic deletions proved by FISH analyses. Of the patients with microscopical deletion (n = 17), only six had classical DGA (n = 4) or VCFS (n = 2) phenotypes. The other 11 had various forms of congenital heart defects as the only presenting signs of deletion. One patient with DGA stigmata had another chromosomal aberration of monosomy 10p13. Only 10 patients were found to have neither cytogenetic nor molecular abnormalities. Therefore, it appeared that the majority, if not all, of the DGA and VCFS patients with the 22q11 deletion were identifiable using FISH with the single N25 (D22S75) probe. It would also be advisable that children with isolated CTD should be carefully examined to detect the other morphologic abnormalities of DGA and VCFS, or CATCH 22 (cardiac defects, abnormal facies, thymic hypoplasia/aplasia, cleft palate, hypocalcemia, and 22q11 deletion). Once these abnormalities are found, a molecular cytogenetic analysis for the so-called 22q11 region is indicated. Because of other associated chromosomal findings, routine or high-resolution cytogenetic analysis should be performed on patients with suspected CATCH 22.