Fragile sites are associated with numerous disorders and diseases, both
heritable and not. The FRAXA site is perhaps most famous for its role in
Fragile X syndrome, but fragile sites are clinically implicated in many other important diseases, such as
cancer.
FRA3B and
FRA16D lie within the large tumor-suppressor genes,
FHIT and
WWOX, respectively. High frequency of deletions at breakpoints within these fragile sites has been associated with many cancers, including breast, lung, and gastric cancers (for review, see Chromosomal alterations may lead to deregulation of microRNA, which could be of diagnostic and prognostic significance for cancers. Additionally, the
Hepatitis B virus (HBV) and HPV-16 virus, the strain of
human papilloma virus most likely to produce cancer, appear to integrate preferentially in or around fragile sites, and it has been proposed that this is crucial to the development of certain
tumors. Fragile sites have also been implicated in a variety of syndromes (for a review, see ). For example, breakage at or near the FRA11b locus has been implicated in
Jacobsen syndrome, which is characterized by loss of part of the long arm of
chromosome 11 accompanied by mild intellectual disability. The FRAXE site is associated in the development of a form of intellectual disability without any distinctive phenotypic features. ==Fragile sites and affected genes==