Unusually mild manifestations of dup(15) (q21.2-qter) in a patient with an unbalanced t(X;15) (q26;q21.2)
- Detroit Medical Center, MI (United States); and others
A 4.5 year old girl was noted to have seizures from age 6 months to 18 months. Delayed psychomotor development was noted by 14 months. At 4.5 years of age, she functioned at 2.5-3 year old level. Her gross motor skills were at 4 year level but expressive language was at 1 year level. Clinical manifestations at 4.5 years included normal physical growth (the weight, height, head circumference were consistently at 50th centile since birth), mild micrognathia, alternating esotropia, deeply grooved philtrum like her mother, slightly low set ears, clinodactyly of left 5th finger and 2nd toes. EEG repeatedly showed generalized paroxysmal activity although no more clinical seizures were noted. Karyotype showed 46,X,der(X)t(X;15)(q26.1;q21.2)mat chromosome consititution resulting in a net duplication of 15q21.2-qter and deletion of Xq26-qter. Karyotypes of the mother and maternal grandmother were 46,X,t(X;15)(q26;q21.2). Review of the literature showed about 38 cases of duplication of distal 15q, only 1 of which involved an X;autosome translocation. These showed moderate to severe mental deficiency and significant dysmorphic features. X inactivation studies using R-banding after BrDU incorporation showed the der(X) to be late replicating (genetically active). In the mother, the normal X appeared to be late replicating. The milder phenotype of the proband suggests that the preferential inactivation of the der(X) spread to the 15q portion even though the autosomal segment was not late replicating. Thus the replication pattern of der(X) in unbalanced X-autosome translocations may be independent of activation or inactivation of autosomal genes.
- OSTI ID:
- 133646
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0376
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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