J Med Genet 2000;37:58-61 ( January )

Short report

Cryptic subtelomeric translocations in the 22q13 deletion syndrome Verayuth Praphanphoj^{a d}, Barbara K Goodman^{b d}, George H Thomas^{a d}, Gerald V Raymond^{c d}

^a Department of Pediatrics, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA, ^b Department of Gynecology and Obstetrics, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA, ^c Department of Neurology, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA, ^d Kennedy Krieger Institute, Baltimore, MD, USA

Correspondence to: Dr Raymond, Room 500, Kennedy Krieger Institute, 707 North Broadway, Baltimore, Maryland, USA

Revised version received 9 July 1999; Accepted for publication 16 August 1999

Cryptic subtelomeric rearrangements are suspected to underlie a substantial portion of terminal chromosomal deletions. We have previously described two children, one with an unbalanced subtelomeric rearrangement resulting in deletion of 22q13qter and duplication of 1qter, and a second with an apparently simple 22q13qter deletion. We have examined two additional patients with deletions of 22q13qter. In one of the new patients presented here, clinical findings were suggestive of the 22q13 deletion syndrome and FISH for 22qter was requested. Chromosome studies suggested an abnormality involving the telomere of one 22q (46,XX,?add(22)(q13.3)). FISH using Oncor D22S39 and Vysis ARSA probes confirmed a terminal deletion. A multi-telomere FISH assay showed a signal from 19qter on the deleted chromosome 22. Results were confirmed with 19qtel and 22qtel specific probes. The patient is therefore trisomic for 19qter and monosomic for 22qter. The patient's mother was found to have a translocation (19;22)(q13.42;q13.31). We also re-examined chromosomes from two patients previously diagnosed with 22q deletions who were not known to have a rearrangement using the multi-telomere assay. One of these patients was found to have a derivative chromosome 22 (der(22)t(6;22)(p25;q13)). No evidence of rearrangement was detected in the other patient. Thus we have found the 22q13 deletion to be associated with a translocation in three of four patients. This report illustrates the usefulness of examining patients with hypotonia, severe language delay, and mild facial dysmorphism for this syndrome and suggests that most of these deletions may be unbalanced subtelomeric rearrangements.


Keywords: multi-telomere FISH; partial monosomy 22q; 22qter deletion syndrome; subtelomeric rearrangement

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© 2000 by J Med Genet
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