J Korean Med Sci.  2008 Aug;23(4):573-578. 10.3346/jkms.2008.23.4.573.

Screening of Subtelomeric Rearrangements in 100 Korean Pediatric Patients with Unexplained Mental Retardation and Anomalies Using Subtelomeric FISH (Fluorescence In Situ Hybridization)

• Park HK
• Kim HJ
• Kim HJ
• Han SH
• Kim YJ
• Kim SH

• KMID: 1785812
• DOI: http://doi.org/10.3346/jkms.2008.23.4.573

Abstract

Rearrangements of the subtelomeric regions of chromosomes account for a significant proportion of the underlying genetic defects in both idiopathic mental retardation (MR) and multiple congenital anomalies. To detect the rearrangements, a set of subtelomeric fluorescence in situ hybridization (FISH) probes has been developed. The aim of this study was to reveal the frequency of subtelomeric rearrangements in Korean patients with MR or multiple anomalies. We performed a FISH study using a commercially available subtelomeric FISH probes on a series of unrelated Korean pediatric patients with MR or multiple anomalies without identifiable causes. We used a checklist to evaluate the developmental delay and/or MR. Patients who were shown to have chromosome abnormalities, metabolic disorders, or recognizable dysmorphic syndromes by clinical and laboratory findings were excluded. As a result, 100 patients were eligible for the Subtelomeric FISH study, and a total of 29 patients (29%) were suspected to have subtelomeric rearrangements on initial screening by the multiprobe FISH kit. Among theses, confirmatory FISH studies by using single locus-specific FISH probes were performed in 24 patients. One patient (a 10- yr-old girl) was confirmed to have rearrangement, deletion of the telomeric portion of the short arm of chromosome 4 (4p). Her clinical manifestation was compatible with Wolf-Hirschhorn syndrome, which is known to be caused by 4p deletion. The frequency of subtelomeric rearrangements in this study was 1.1% (1/95), lower than those previously reported (0.5-16.3%). We suggest that subtelomeric FISH test is a useful screening tool for patients with idiopathic MR and/or dysmorphism regardless of its false positive value.

Keyword

Chromosomal Rearrangement; Idiopathic Mental Retardation; Subtelomeric FISH

MeSH Terms

Adolescent
Adult
Child
Child, Preschool
Congenital Abnormalities/*genetics
Female
Gene Rearrangement
Humans
In Situ Hybridization, Fluorescence/*methods
Infant
Male
Mental Retardation/*genetics
*Telomere

Figure

• 

  Fig. 1 (A) Metaphases fluorescence in situ hybridization (FISH) using subtelomeric multiprobes showed one normal chromosome 4 with red signals from the subtelomeric region of the long arm and green signals from the subtelomeric region of the short arm (arrow) and the other copy of chromosome 4 lacking the green signals (headarrow), indicating the deletion of the subtelomeric region of the short arm of chromosome 4. (B) We confirmed the finding from the multiprobes using a single probe for 4p. Only one chromosome 4 revealed signals from 4p (arrow), indicating deletion of 4p telomere in the other copy of chromosome 4 (headarrow). (C) Partial G-banded karyotype of chromosome 4 of this patient. Chromosomal abnormality was not detected via conventional cytogenetic analysis.

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