Major translocations in genetic counselling
Authors: József Gábor Joó, Ákos Csaba, Zsanett Szigeti, Judit Nagy Oroszné, János Rigó jr
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To review major chromosome translocation, with special regard to the clinical differences between balanced and unbalanced, as well as de novo and inherited cases.
The authors have included cases of major chromosome translocations detected during a 20-year period. Among the 28 cases, 25 patients carried balanced and 3 were affected by unbalanced translocations.
In cases of balanced translocation, maternal age ranged between 26 and 42 years, with a median age value of (30.5±2.67) years, while in unbalanced translocations the values were between 24-37 with a median age of (30.5±4.59) years. In three cases (13%) of balanced translocations in the patient's history previous chromosomal aberrations had been recorded. In nine cases of the same group (39%) previous miscarriages were reported. In cases in which balanced translocation was suspected, karyotyping was done in the 16th-23rd gestational weeks. In three cases of unbalanced translocation, karyotyping was performed in weeks 18 or 19. Among the 28 cases examined by us, 12 carried reciprocal and 16 were affected by Robertsonian translocations. If the involvement of chromosomes in balanced translocations was concerned, chromosome 14 was found to be overwhelmingly affected. In 14 of the 25 cases (56%) examined by us, this chromosome was definitely affected by translocation. Frequently occurring translocations in chromosomes 1, 13 and 22 are also worth mentioning.
Ultrasonography performed after karyotyping-in the cases of balanced translocations-and the results of fetal echocardiography-if such imaging was done at all-provide important information about the prognosis of the fetus. In case of sonographically normal fetal anatomy the good outcome of pregnancy is probable, while in cases of unbalanced translocations the sonography reconfirms the chances of poor outcome.
Serum-alfa fetoprotein screening