We refer 55 cases of the chromosomal instability syndromes (SCI), diagnosed in patients of our genetical clinics.
Problems of early diagnosis can be documented by a discrepancy between the expected number of patients and their
relative advanced age at the time when SCI was ascertained. We have also shown that NBS patients can be diagnosed
earlier and the disease sufficiently confirmed on the basis of congenital microcephaly and on the direct detection of
657del5 mutation in NBS1 gene. Genealogical analysis of families with SCI revealed a low risk of prenatal selection
of affected homozygotes and high cancer prevalence in relative (in NBS families recognized heterozygotes) at young
adult age. Due to severe DNA repair disorder and hyperradiosensitivity of affected homozygotes as well as unaffected
heterozygotes, conventional diagnostics and treatment protocols of lymphoreticular malignancies in affected
homozygotes are prohibited. The use of Nijmegen treatment protocol improved in our patients dramatically their
clinical prognosis, which is documented by 6 NBS patients surviving one or two malignancies. Early diagnose of
SCI and information for families and their doctors about consequences of DNA repair disorder and about their
hyperradiosensitivity is essential for improving the clinical prognosis of SCI patients.
genetic instability, Nijmegen breakage syndrome, malignancies, radiosensitivity, microcephaly,