Partial trisomy 8q. Two case reports with maternal translocation and inverted insertion: phenotype analyses and reflections on the risk.

Partial trisomy 8qter-->q23 or q24.1 has been reported in 15 literature cases. We add two further case reports here. Patient 1 inherited the derivative (2) of a balanced maternal reciprocal translocation t(2;8)(qter;q2300) after 2:2 disjunction and adjacent-1 segregation, and is trisomic for the segment 8qter-->q2300. Patient 2 inherited a recombinant (8) of a balanced maternal inverted insertion inv ins(8)(q1300;q2300q24.2) and is trisomic for the segment 8q24.2-->q2300. The phenotype of both patients is described and compared to the spectrum of symptoms established from the 15 literature cases. This spectrum contains all features observed with a frequency of > = 50%. Patient 1 had 35% of the features of this spectrum; Patient 2 had 47%. The intrauterine survival probability of unbalanced offspring is assumed to be the same in both cases, as nearly the same segments are trisomic. The pedigrees indicate that the inversion carrier may have a reduced production probability of unbalanced gametes and therefore a reduced risk compared to the translocation carrier.