[Genetic risk of families with t(1;2)(q42;q33) GTG, RHG, QFQ, FISH]

A central concept in genetic counseling is the estimation of the probability of recurrence of unfavourable pregnancy outcomes (abortion, stillbirth and birth at malformed child). In case of chromosomal changes estimates are made on basis of segregation analyses in actual pedigree. If we have a few of pedigree members than risk estimate should be performed on basis combined our data and empiric data from literature. We present individual genetic risk for carriers of unique reciprocal translocation t(1;2)(q42;q33) detected through karyotyping of the patient with miscarriage.

The pedigree consisted 5 families of t(1;2)(q42;q33) carriers with 15 members of progeny was evaluated according to Stene and Stengel-Rutkowski. Cytogenetic analysis of persons of these families (7 persons) was performed on blood samples using GTG, RHG, QFQ and FISH techniques. Additional RCT pedigree analysis of Stengel-Rutkowski et at Collection, Polish Collection, Lituanian Collection, Bielorussian Collection and an available literature cases were performed.

The translocation was classified as translocation at risk for double segment imbalances for trisomy 1q42-->qter together with monosomy 2q33-->qter or monosomy 1q42-->qter together with trisomy 2q33-->qter after 2:2 disjunction after adjacent-1 segregation of the meiotic chromosomes. Two improved risk values for RCT with segments 1q42-->qter, 2q33-->qter were obtained i.e. 6/44 (13.6% +/- 5.2%) and 4/20 (20% +/- 8.9%). The probability of occurrence for this translocation carriers was estimated as 7% (medium risk). On basis of direct analysis at presented pedigree a risk for miscarriage was estimated as 2/9.

1. Carrierships of t(1;2)(q42;q33) increased population risk value for unbalanced progeny at birth by 7% (medium risk) and for miscarriage 2/9. 2. Causative relation between presence of t(1;2)(q42;q33) and miscarriages is suggested. 3. Updated, new genetic risk values for RCT at risk for single segment 1q42-->qter imbalance is 6/44 (13.6% +/- 5.2%) at birth and for single segment 2q33-->qter imbalance is 4/20 (20% +/- 8.9%).