DE-NOVO DER(X)T(X-10) (Q26-Q21) WITH FEATURES OF DISTAL TRISOMY 10Q -CASE-REPORT OF PATERNAL ORIGIN IDENTIFIED BY LATE REPLICATION WITH BRDU AND THE HUMAN ANDROGEN RECEPTOR ASSAY (HAR)

We describe an 11 year old girl with a de novo unbalanced t(X;10) that resulted in a deletion of Xq26-->Xqter and a trisomy of 20q21-->10qte r. Her clinical features were of distal trisomy 10q, but she lacked th e cardiovascular and renal malformations observed in duplications of 1 0q24-->10qter and had only moderate mental retardation. X inactivation was assessed on peripheral blood lymphocytes by late replication with BrdU (LR) and the human androgen receptor assay (HAR). By LR the der( X) was inactive without spreading to 10q21-->10qter in all cells. The HAR assay showed skewed methylation of the paternal allele (90%). The correlation of HAR and LR suggests that the der(X) was paternally inhe rited and is consistent with data from other de novo balanced and unba lanced X;autosome translocations detected in females. This is the firs t report of parental origin of a de novo trisomy 10q.