title: Interchange trisomy 21 by t(1;21)(p22;q22)mat.
abstract: Interchange trisomy 21 by t(1:21)(p22:q22)mat: Interchange trisomy 21 by t(1;21)(p22;q22)mat was identified in a sporadic patient with Down syndrome. With a 21q22 specific probe, we observed signals on both normal 21 chromosomes and on the der. We reviewed the 23 published reports of families with reciprocal translocations leading to viable offspring with interchange trisomy 21. The breakpoints in chromosome 21 were mainly located in 21q (19/24 instances, including the present report) and in 19/23 cases the other chromosome involved in the translocation was <<large>> (pairs 1-12). The underlying 3:1 segregation occurred mainly in carrier mothers; only one patient presented a de novo imbalance and in another case the father was the carrier. In addition, there were 4 instances of concurrence with another unbalanced segregation (adjacent-1 or tertiary trisomy) and 3 families with recurrence of interchange trisomy 21. The mean age of 14 female carriers at birth of interchange trisomy 21 offspring (24.8 yr) was lower that the mean (28.3 yr) found in a larger sample of mothers of unbalanced offspring due to 3:1 segregation (mostly tertiary trisomics) and was not increased with respect to the general population average. Overall, these data agree with previous estimates regarding recurrence risk (9-15%) and abortion rate (about 28%) in female carriers ascertained through an interchange trisomic 21 child.
authors.affiliation: Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco.
authors.forename: M G
authors.initials: MG
authors.lastname: Dominguez
authors.forename: H
authors.initials: H
authors.lastname: Rivera
authors.forename: A I
authors.initials: AI
authors.lastname: Vasquez
authors.forename: G
authors.initials: G
authors.lastname: Hernández-Zaragoza
authors.forename: F
authors.initials: F
authors.lastname: Rivas
mesh_terms: D000328:Adult; D002878:Chromosomes, Human, Pair 1; D002891:Chromosomes, Human, Pair 21; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D011247:Pregnancy; D014178:Translocation, Genetic; D014314:Trisomy