Nijmegen breakage syndrome

Nijmegen breakage syndrome (NBS), also known as Berlin breakage syndrome and Seemanova syndrome, is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the Double Holliday junction DNA repair mechanism.

NBS1 codes for a protein that has two major functions: (1) to stop the cell cycle in the S phase, when there are errors in the cell DNA (2) to interact with FANCD2 that can activate the BRCA1/BRCA2 pathway of Dna repair. This explains clearly that mutations in the NBS1 gene lead to higher levels of cancer (see Fanconi anemia, cockayne syndrome...)

The name derives from the Dutch city Nijmegen where the condition was first described.

Most people with NBS have West Slavic origins. The largest number of them live in Poland.

Mrs.Seemanova MD after whom the name of the syndrome was given, currently works at Motol Hospital, Prague, Czech Republic, as a Professor of medical genetics.

Characteristics
It is characterized by microcephaly, a distinct facial appearance, short stature, immunodeficiency, radiation sensitivity and a strong predisposition to lymphoid malignancy.

Cause and Genetics
NBS is caused by a mutation in the NBS1 gene, located at human chromosome 8q21. The disease is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 8 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.