Ring chromosome 20 with loss of telomeric sequences detected by multicolour PRINS.
A ring chromosome 20 in a male infant with epileptic seizures, mental and somatic growth retardation, and behavioural disturbances is described. Conventional cytogenetics revealed the karyotype to be 46,XY,r(20)(pter-->qter) and no signs of mosaicism were found. Fluorescence in situ hybridisation using the clone p20Z1 identified the ring to be derived from chromosome 20. By counting 111 metaphases, only 7% were found to be missing the ring. The absence of telomeric sequences in the ring chromosome was demonstrated by multicolour PRINS: a three-step PRimed IN Situ labelling technique, using unlabelled primers. A terminal deletion of both arms thus seems to be the cause of the ring formation in the proband. Bivariate flow-analysis of chromosomes verified a deletion of the ring chromosome. The clinical and cytogenetic findings are compared with previous cases. A specific ring 20 syndrome seems justified.
Brandt
C A
CA
Institute of Human Genetics, University of Aarhus, Denmark.
Kierkegaard
O
O
Hindkjaer
J
J
Jensen
P K
PK
Pedersen
S
S
Therkelsen
A J
AJ
D000015:Abnormalities, Multiple / Q000235:genetics*; D000243:Adenosine Deaminase / Q000096:biosynthesis; D000374:Aggression; D002871:Chromosome Banding; D002872:Chromosome Deletion; D002890:Chromosomes, Human, Pair 20; D004827:Epilepsy / Q000235:genetics; D004912:Erythrocytes / Q000201:enzymology; D005434:Flow Cytometry; D005500:Follow-Up Studies; D006130:Growth Disorders / Q000235:genetics; D006801:Humans; D017403:In Situ Hybridization; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics; D007621:Karyotyping; D008297:Male; D012303:Ring Chromosomes; D016615:Telomere / Q000648:ultrastructure
D000243:Adenosine Deaminase