???aural:Bildanfang???A lack of RAD50 proteins damages the chromosomes. The genetic ferries break apart or swap fragments. The figure shows the latter. The green fragment is from another chromosome.   © Institute for Human Genetics, University of Würzburg???aural:Bildende???

An international team of scientists has discovered an unknown defect in a young
woman's genetic material. Her body cannot repair some forms of DNA damage. DNA is damaged continuously, both by UV radiation and toxic environmental substances.

Often, the body can repair such damage, including DNA double-strand breaks. In such cases, the so-called MRN protein complex comes into action first. It helps find the damage and informs the cell's repair system. However, it is not effective in this young woman. "We've known the patient for 15 years," says Prof. Detlev Schindler of the University of Würzburg. We first thought she had Nijmegen Breakage Syndrome (NBS), a congenital disease caused by one of the two defects of the protein complex known at that time.

It only affects one in three million people. Her symptoms are typical: microcephaly, retarded growth, physical and mental retardation. Over time, it became clear that she was different, since she has normal immune defence and showed no signs of serious NBS complications: No serious respiratory infections, which often kill NBS patients, and no signs of lymph node cancer. Now we know why. It's not NBS, but a new disease, called: "NBS-like disorder". Previously unknown, it has now been characterised by researchers at the University of Würzburg and colleagues from Germany, Israel and Australia.

More information: www.uni-wuerzburg.de/en