Rare hereditary diseases with defects in DNA-repair.

The human genome is constantly exposed to various sources of DNA damage. Ineffective protection from this damage leads to genetic instability which can ultimately give rise to somatic disease, causing mutations. Therefore our organism commands a number of highly conserved and effective mechanisms responsible for DNA repair. If these repair mechanisms are defective due to germline mutations in relevant genes, rare diseases with DNA repair deficiencies can arise. Today, a limited number of rare hereditary diseases characterized by genetic defects of DNA repair mechanisms is known, comprising ataxia telangiectasia, Nijmegen breakage syndrome, Werner syndrome, Bloom Syndrome, Fanconi anemia, xeroderma pigmentosum, Cockayne syndrome, trichothiodystrophy. Although heterogeneous in respect to selected symptoms, these rare disorders share many clinical features such as growth retardation, neurological disorders, premature ageing, skin alterations including abnormal pigmentation, telangiectasia, xerosis cutis, pathological wound healing as well as an increased risk of developing different types of cancer. Based on the clinical similarities of symptoms as well as the predominant diagnostic technology available, many of these rare disorders were formerly classified as genodermatoses with cancer predisposition or chromosomal breakage symptoms. These pathological conditions not only severely impair patients with these rare genetic diseases but also represent symptoms affecting large parts of the general population.