Bloom syndrome (often abbreviated as BS in literature)[1] is a rare autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability.

Cells from a person with Bloom syndrome exhibit a striking genomic instability that includes excessive crossovers between homologous chromosomes and sister chromatid exchanges (SCEs).

The rash is variably expressed, being present in a majority but not all persons with Bloom syndrome, and it is on average less severe in females than in males.

There are other dermatologic changes, including hypo-pigmented and hyper-pigmented areas, cafe-au-lait spots, and telangiectasias, which can appear on the face and on the ocular surface.

[citation needed] There is a characteristic facial appearance that includes a long, narrow face; prominent nose, cheeks, and ears; and micrognathism or undersized jaw.

[5] Infants can exhibit frequent gastrointestinal upsets, with reflux, vomiting, and diarrhea, and there is a remarkable lack in interest in food.

There are endocrine disturbances, particularly abnormalities of carbohydrate metabolism, insulin resistance and susceptibility to type 2 diabetes, dyslipidemia, and compensated hypothyroidism.

The features of BSLD include small size and dermatologic findings, such as cafe-au-lait spots, and the presence of the once pathognomonic elevated SCEs is reported for persons with mutations in TOP3A and RMI1.

[10][11] Bloom syndrome shares some features with Fanconi anemia possibly because there is overlap in the function of the proteins mutated in this related disorder.

[12] Bloom syndrome is an autosomal recessive disorder, caused by mutations in the maternally- and paternally-derived copies of the gene BLM.

[14] The cells from persons with Bloom syndrome exhibit a striking genomic instability that is characterized by hyper-recombination and hyper-mutation.

Human BLM cells are sensitive to DNA damaging agents such as UV and methyl methanesulfonate,[15] indicating deficient repair capability.

[16] The hyper-recombination can also be detected by molecular assays [17] The BLM gene encodes a member of the protein family referred to as RecQ helicases.

[19] Disruption of the proper assembly of the Bloom Syndrome complex leads to genome stability, genetic dependence on cellular nucleases GEN1 and MUS81, and loss of normal cell growth.

[10] As noted above, there is a greatly elevated rate of mutation in Bloom syndrome and the genomic instability is associated with a high risk of cancer in affected individuals.

[24] Persons with Bloom syndrome have an enormous increase in exchange events between homologous chromosomes or sister chromatids (the two DNA molecules that are produced by the DNA replication process), and there are increases in chromosome breakage and rearrangements compared to persons who do not have Bloom's syndrome.

[8] Bloom syndrome has no specific treatment; however, avoiding sun exposure and using sunscreens can help prevent some of the cutaneous changes associated with photo-sensitivity.