Mosaicism for an ectopic NOR at 8pter and a complex rearrangement of chromosome 8 in a patient with severe psychomotor retardation.
We describe a 3-year-old girl with severe delays in mental and motor skills, a history of generalized seizures, and subtle dysmorphic features. Conventional cytogenetics revealed a mosaic karyotype. A de novo ectopic NOR at the telomeric region of the short arm of one chromosome 8 (8ps) was found in 90% of lymphocyte and in 98% of fibroblast metaphases. A small NOR-bearing marker chromosome and a large derivative chromosome 8 without short arm satellites (der(8)) were present in the remaining cells. FISH with a probe specific for centromeres 14 and 22 labeled both the telomeric region of 8ps and the small marker centromere. Der(8) included an inverted duplication of 8p and a rearranged duplication of 8q but lacked a second centromere. A subtelomeric probe for 8p revealed a cryptic deletion in 8ps and der(8). Thus, the karyotype represents a combination of submicroscopic partial monosomy 8pter and mosaic trisomy 8.
Felbor
U
U
Department of Human Genetics, University of Würzburg, Biozentrum, Würzburg, Germany.
Knötgen
N
N
Schams
G
G
Buwe
A
A
Steinlein
C
C
Schmid
M
M
D002503:Centromere / Q000473:pathology; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D002898:Chromosomes, Human, Pair 8 / Q000648:ultrastructure*; D004829:Epilepsy, Generalized / Q000150:complications / Q000235:genetics; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000150:complications / Q000235:genetics*; D009030:Mosaicism; D009697:Nucleolus Organizer Region / Q000473:pathology; D011596:Psychomotor Disorders / Q000150:complications / Q000235:genetics; D014314:Trisomy