Mosaic trisomy of a small r(1) with an abnormal phenotype.
Cytogenetic studies of a mildly dysmorphic 10-year-old male with mild developmental delay and learning difficulties revealed mosaicism for a supernumerary ring chromosome in approximately half of the cells. The karyotype of this patient was established as 47,XY,+r[15]/46,XY[15].ish r(1)(D1Z7+,wcp1-). Although the presence of euchromatic material was shown by C banding, the lack of hybridization with the whole chromosome paint 1 (wcp1) probe suggests that few unique sequences are contained in the ring and that these sequences likely explain the child's dysmorphic features and developmental delay. A review of the literature, including the present case, suggests that the significance of euchromatin in supernumerary r(1) as determined by both C banding and fluorescence in situ hybridization (FISH) with chromosome 1 painting probes can be used as a prognostic indicator for potential severity of the clinical phenotype.
Dawson
A J
AJ
Cytogenetics Laboratory, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba, Canada. adawson@hsc.mb.ca
Konkin
D
D
Riordan
D
D
Chudley
A E
AE
D002648:Child; D002871:Chromosome Banding; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D012303:Ring Chromosomes; D014314:Trisomy