58 J Med Genet 2000;37:58–61 Cryptic subtelomeric translocations in the 22q13 deletion syndrome J Med Genet: first published as 10.1136/jmg.37.1.58 on 1 January 2000. Downloaded from Verayuth Praphanphoj, Barbara K Goodman, George H Thomas, Gerald V Raymond Abstract lieved to result from de novo, simple, subtelom- Cryptic subtelomeric rearrangements eric deletions,1–9 two cases were derived from are suspected to underlie a substantial balanced translocations,49 one case was the portion of terminal chromosomal dele- result of a familial chromosome 22 inversion,10 tions. We have previously described two and in one case the mechanism was not children, one with an unbalanced subtelo- determined.11 (It is possible that one of these meric rearrangement resulting in dele- cases may have been reported twice,17in which tion of 22q13→qter and duplication of case the total number would be 21 cases and the 1qter, and a second with an apparently simple deletions would be 17 cases.) This report simple 22q13→qter deletion. We have describes the clinical findings in a new case of examined two additional patients with 22q13→qter deletion and the identification of deletions of 22q13→qter. In one of the new translocated material on the deleted chromo- patients presented here, clinical findings some using multi-telomere fluorescence in situ were suggestive of the 22q13 deletion syn- hybridisation (FISH). drome and FISH for 22qter was re- Recent data indicate that some apparently quested. Chromosome studies suggested terminal chromosome deletions are, in fact, an abnormality involving the telomere of derivative chromosomes involving cryptic termi- one 22q (46,XX,?add(22)(q13.3)). FISH nal rearrangements.12 13 It is important to detect using Oncor D22S39 and Vysis ARSA and identify the presence of subtelomeric mate- probes confirmed a terminal deletion. A rial from other chromosomes in these deletions multi-telomere FISH assay showed a sig- in order to establish accurate karyotype- nal from 19qter on the deleted chromo- phenotype associations as well as to provide some 22. Results were confirmed with important genetic information to the parents 19qtel and 22qtel specific probes. The and the family members. One of the methods patient is therefore trisomic for 19qter used to investigate cryptic chromosomal abnor- and monosomic for 22qter. The patient’s malities in patients with unexplained mental 12 Department of mother was found to have a translocation retardation is multi-telomere FISH. This tech- Pediatrics, The Johns (19;22)(q13.42;q13.31). We also re- nique simultaneously detects all human telo- Hopkins University, examined chromosomes from two pa- meric regions on a single microscope slide using School of Medicine, tients previously diagnosed with 22q chromosome specific subtelomeric probes. We http://jmg.bmj.com/ Baltimore, MD, USA deletions who were not known to have a used this method to further analyse samples V Praphanphoj from patients in whom there was evidence G H Thomas rearrangement using the multi-telomere assay. One of these patients was found to suggesting the presence of a terminal chromo- Department of have a derivative chromosome 22 somal deletion or rearrangement. We studied → Gynecology and (der(22)t(6;22)(p25;q13)). No evidence of three patients known to have 22q13 qter dele- Obstetrics, The Johns tions in which the presence of translocated Hopkins University, rearrangement was detected in the other patient. Thus we have found the 22q13 material was either not suspected or was in School of Medicine, question. Including our previously reported case on October 1, 2021 by guest. Protected copyright. Baltimore, MD, USA deletion to be associated with a transloca- B K Goodman tion in three of four patients. This report (case 1 in reference 9), three of four deletion illustrates the usefulness of examining 22q13 cases investigated were, in fact, derivative Department of patients with hypotonia, severe language chromosomes resulting from subtle or cryptic Neurology, The Johns translocations. Hopkins University, delay, and mild facial dysmorphism for School of Medicine, this syndrome and suggests that most of Case report Baltimore, MD, USA these deletions may be unbalanced subte- The proband wasa4yearoldfemale who G V Raymond lomeric rearrangements. presented for evaluation of hypotonia, develop- (J Med Genet 2000;37:58–61) Kennedy Krieger mental delay, small stature, and microcephaly. Institute, Baltimore, Keywords: multi-telomere FISH; partial monosomy She was the 3204 g product of a 38 year old MD, USA 22q; 22qter deletion syndrome; subtelomeric rearrange- gravida 1. She was noted to have been inactive in V Praphanphoj ment utero, although ultrasound and amniocentesis B K Goodman studies carried out because of maternal age were G V Raymond G H Thomas Patients with the terminal 22q13 deletion unremarkable. Delivery was uncomplicated. syndrome share a number of clinical features, Problems in the newborn period included Correspondence to: including severe expressive language delay, gen- enlargement of the clitoris and subsequently Dr Raymond, Room 500, eralised hypotonia, developmental delay, and delay in acquisition of motor milestones devel- Kennedy Krieger Institute, 1 707 North Broadway, mild facial dysmorphism. The increasing oped. At 9 months, she was hypotonic and was Baltimore, Maryland, USA number of patients being reported suggests that not yet sitting. She sat at 12 months and walked this may be yet another important form of men- at 2 years. During the first year of life, there were Revised version received tal retardation resulting from a small terminal concerns about feeding and at 12 months she 9 July 1999 Accepted for publication deletion. Since first described in 1985, 22 cases was placed on a nutritional supplement, after 16 August 1999 have been reported. Eighteen cases were be- which she gained weight. Cryptic subtelomeric translocations in the 22q13 deletion syndrome 59 On examination at 4 years 5 months, her head mosomal karyotype and FISH analysis for circumference was 46.5 cm (<2nd centile), evaluation for a possible 22q terminal deletion. J Med Genet: first published as 10.1136/jmg.37.1.58 on 1 January 2000. Downloaded from height 90.9 cm (<5th centile), and weight 13.8 kg (<5th centile). She was alert and only mildly Material and methods dysmorphic with mild flattening of the nasal Prometaphase chromosomes were prepared bridge and the midface. She was very sociable using synchronised peripheral blood lym- and interactive. Although by history she does phocytes.14 Chromosomes were G banded by use sounds for four or five objects, no words Wright stain using trypsin (GTW) and ana- were spoken. She could vocalise, point to some lysed under the light microscope. FISH was body parts, and follow one or two step performed using standard techniques, with commands. She had moderate hypotonia, but rapid wash conditions (72°C, 2 × SSC) and no normal muscle mass and good strength. Sensa- signal amplification. Slides were counter- tion was intact. There was no ataxia. She was stained with either propidium iodide or DAPI able to walk and rise from the floor without dif- depending on the fluorophores used. The ficulty. Her reflexes were diminished. following probes were used for analysis of the Magnetic resonance imaging at 2 years 22qter region: STS WI-941 and D22S39 showed colpocephaly, a decrease in the peri- (Oncor) and ARSA (Vysis). These probes were ventricular white matter with some delay in originally developed as control probes for the white matter myelination, and a cerebellar DiGeorge critical region probes and were arachnoid cyst. A second MRI performed at a commercially available for that purpose. Spe- later age showed an increase in myelination and cific subtelomeric probes (Vysis) containing no progression of any abnormalities. Labora- the loci D19S238E (mapped to 19qtel), tory studies indicated normal lactic acid, MS607 (mapped to 22qtel), and a probe still plasma amino acids, and urinary organic acids. under development (mapped to 6ptel) were Secondary to her presentation and with our also used to confirm the findings obtained from previous experience, blood was sent for chro- multi-telomere analysis. http://jmg.bmj.com/ on October 1, 2021 by guest. Protected copyright. Figure 1 FISH analysis of the patient. (A) Vysis DiGeorge probe cocktail (TUPLE1 red, ARSA green); arrow indicates deleted 22. (B) Oncor dual color DiGeorge probe cocktail (D22S75 red, WI-941 green); arrows indicate signal for WI-941 on both chromosomes 22. (C) Cytocell Multiprobe-T device, section 19 (short arm green, long arm red); arrow indicates red signal (long arm) on one chromosome 22. (D) Vysis 19qtel specific probe (red); arrows indicate signals on both chromosomes 19 and the der(22) chromosome. 60 Praphanphoj, Goodman, Thomas, et al The multi-telomere FISH assay (Cytocell Results Chromoprobe Multiprobe-T) was carried out High resolution chromosome analysis (650 J Med Genet: first published as 10.1136/jmg.37.1.58 on 1 January 2000. Downloaded from on peripheral blood lymphocytes according to bands) of the proband showed a subtle abnor- the manufacturer’s instructions. Two µl of fixed mality at the terminal end of one chromosome cell suspension were applied to each square 22. While a terminal deletion, rearrangement, area of the 24 square multiprobe sample slides or exchange was suspected, the abnormality and then flooded with 3:1 methanol:acetic acid was too subtle to permit the precise nature of solution. Metaphase spread quality was evalu- the alteration to be determined. FISH analysis ated using phase contrast and the slides were using Oncor D22S39 (not shown) and Vysis aged overnight at room temperature. The next ARSA (arylsulfatase A locus) (fig 1A) probes day, the slides were incubated in 2 × SSC for indicated a terminal deletion of the abnormal two minutes at room temperature and dehy- chromosome 22, while the Oncor STS WI-941 drated serially for two minutes each in 75%, probe (fig 1B), which hybridised more proxi- 80%, and 95% cold ethanol.