[Nijmegen Breakage syndrome].

Debreceni Egyetem, Orvos- és Egészségtudományi Centrum Infektológiai és Gyermekimmunológiai Tanszék, Debrecen.
Orvosi Hetilap 04/2010; 151(16):665-73. DOI: 10.1556/OH.2010.28851
Source: PubMed

ABSTRACT Nijmegen Breakage syndrome is a rare, autosomal recessive disorder characterized by severe, combined immunodeficiency, recurrent sinopulmonary infections, chromosomal instability, radiosensitivity, predisposition to malignancy, a "bird-like" facial appearance, progressive microcephaly, short stature, and mental retardation. The syndrome is caused by mutations in the NBS1 gene, which encodes a DNA-repair protein, named nibrin. The authors summarize current knowledge on molecular genetics, diagnostic characteristics and therapeutic options of this inborn error of innate immunity.

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    ABSTRACT: Many studies were published to evaluate the association between Nijmegen breakage syndrome 1 (NBS1) 657del5 polymorphism and breast cancer risk, but the results remained inconsistent. To derive a more precise estimation on the possible association, we performed a meta-analysis of previous published studies. Case-control studies on the association between NBS1 657del5 polymorphisms and breast cancer risk were included into this meta-analysis. We used the odds ratio (OR) with 95 % confidence interval (95 % CI) to assess the strength of the association. Ten studies with a total of 25,365 subjects were identified and included into this meta-analysis. Meta-analysis of those ten studies showed that there was a significant association between NBS1 657del5 polymorphisms and breast cancer risk (pooled OR = 2.66, 95 % CI 1.82-3.90, P < 0.001). The cumulative meta-analyses showed a trend of a more significant association between NBS1 657del5 polymorphisms and breast cancer risk as data accumulated by publication year. Thus, our meta-analysis suggests that there was a significant association between NBS1 657del5 polymorphisms and breast cancer risk, and NBS1 657del5 polymorphism results in an increased risk of breast cancer.
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    ABSTRACT: Nijmegen breakage syndrome (NBS) is a rare autosomal recessive syndrome of chromosomal instability mainly characterized by microcephaly at birth, combined immunodeficiency and predisposition to malignancies. Due to a founder mutation in the underlying NBN gene (c.657_661del5) the disease is encountered most frequently among Slavic populations. The principal clinical manifestations of the syndrome are: microcephaly, present at birth and progressive with age, dysmorphic facial features, mild growth retardation, mild-to-moderate intellectual disability, and, in females, hypergonadotropic hypogonadism. Combined cellular and humoral immunodeficiency with recurrent sinopulmonary infections, a strong predisposition to develop malignancies (predominantly of lymphoid origin) and radiosensitivity are other integral manifestations of the syndrome. The NBN gene codes for nibrin which, as part of a DNA repair complex, plays a critical nuclear role wherever double-stranded DNA ends occur, either physiologically or as a result of mutagenic exposure. Laboratory findings include: (1) spontaneous chromosomal breakage in peripheral T lymphocytes with rearrangements preferentially involving chromosomes 7 and 14, (2) sensitivity to ionizing radiation or radiomimetics as demonstrated in vitro by cytogenetic methods or by colony survival assay, (3) radioresistant DNA synthesis, (4) biallelic hypomorphic mutations in the NBN gene, and (5) absence of full-length nibrin protein. Microcephaly and immunodeficiency are common to DNA ligase IV deficiency (LIG4 syndrome) and severe combined immunodeficiency with microcephaly, growth retardation, and sensitivity to ionizing radiation due to NHEJ1 deficiency (NHEJ1 syndrome). In fact, NBS was most commonly confused with Fanconi anaemia and LIG4 syndrome. Genetic counselling should inform parents of an affected child of the 25% risk for further children to be affected. Prenatal molecular genetic diagnosis is possible if disease-causing mutations in both alleles of the NBN gene are known. No specific therapy is available for NBS, however, hematopoietic stem cell transplantation may be one option for some patients. Prognosis is generally poor due to the extremely high rate of malignancies.
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