Study of 250 children with idiopathic mental retardation reveals nine cryptic and diverse subtelomeric chromosome anomalies.
Cryptic subtelomeric chromosome anomalies have been recognized as a significant cause of dysmorphology and mental retardation. To determine whether the clinical cytogenetics laboratory should screen routinely for these aberrations, we have tested 250 patients with idiopathic mental retardation/developmental delay, either isolated (53) or associated with dysmorphic features and/or malformations in the absence of a recognizable syndrome (197). All had normal karyotypes at the 550-850 band level. Subtelomeric anomalies were found in 1/53 of the first group (1.9%) and 8/197 of the second group (4.1%). In one patient, two separate anomalies were present: a deletion (not inherited) and a duplication (inherited). It is possible that one of these 10 observed aberrations might represent a rare and previously unreported polymorphism and one a rare cross-hybridization. Our study supports the proposition that cryptic subtelomeric rearrangements are a significant cause of idiopathic mental retardation/developmental delay, but both the diversity of the phenotypes of the positive cases and the wide diversity of their associated chromosome abnormalities emphasize the central problem for the clinical cytogenetics laboratory-that of choosing the most productive patient base for this useful diagnostic test.
Baker
Elizabeth
E
Centre for Medical Genetics, Department of Cytogenetics and Molecular Genetics, Women's and Children's Hospital, Adelaide, Australia.
Hinton
Lyn
L
Callen
David F
DF
Altree
Meryl
M
Dobbie
Angus
A
Eyre
Helen J
HJ
Sutherland
Grant R
GR
Thompson
Elizabeth
E
Thompson
Peter
P
Woollatt
Erica
E
Haan
Eric
E
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D015342:DNA Probes; D005260:Female; D020440:Gene Duplication; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008607:Intellectual Disability / Q000209:etiology / Q000235:genetics*; D008297:Male; D008403:Mass Screening; D010375:Pedigree; D016615:Telomere
D015342:DNA Probes