Bloom syndrome

Infobox_Disease
Name = PAGENAME


Caption =
DiseasesDB = 1505
ICD10 =
ICD9 = ICD9|757.39
ICDO =
OMIM = 210900
MedlinePlus =
eMedicineSubj = derm
eMedicineTopic = 54
MeshID = D001816

Bloom syndrome (BLM) [OMIM|210900] is a rare autosomal recessive [cite journal |pmid=9482582 |year=1998 |month= |author=Straughen, Je; Johnson, J; Mclaren, D; Proytcheva, M; Ellis, N; German, J; Groden, J |title=A rapid method for detecting the predominant Ashkenazi Jewish mutation in the Bloom's syndrome gene |volume=11 |issue=2 |pages=175–8 |doi=10.1002/(SICI)1098-1004(1998)11:2<175::AID-HUMU11>3.0.CO;2-W |journal=Human mutation] chromosomal disorder characterized by a high frequency of breaks and rearrangements in an affected person's chromosomes. The condition was discovered and first described by dermatologist Dr. David Bloom in 1954. [cite journal |author=Bloom D |title=Congenital telangiectatic erythema resembling lupus erythematosus in dwarfs; probably a syndrome entity |journal=A.M.A. American journal of diseases of children |volume=88 |issue=6 |pages=754–8 |year=1954 |pmid=13206391 ]

Presentation

Bloom syndrome is characterized by shortened stature, a higher-pitched voice and distinct facial features including a long, narrow face; small lower jaw, and prominent nose and ears. Affected individuals usually develop pigmentation changes and dilated blood vessels in the skin, particularly in response to sun exposure. These changes often appear as a butterfly-shaped patch of reddened skin on the face. The skin changes may also affect the hands and arms.

Other features of the disorder may include learning disabilities, mental retardation, chronic lung problems, diabetes, and immune deficiency that leads to recurrent pneumonia and ear infections. Men with Bloom syndrome usually do not produce sperm and, as a result, are unable to father children. Women with the disorder generally experience menopause earlier than usual.

Relationship to cancer

Chromosomal instability in Bloom syndrome results in a high risk of cancer in affected individuals.cite journal |author=Amor-Guéret M |title=Bloom syndrome, genomic instability and cancer: the SOS-like hypothesis |journal=Cancer Lett. |volume=236 |issue=1 |pages=1–12 |year=2006 |pmid=15950375 |doi=10.1016/j.canlet.2005.04.023 |url=http://linkinghub.elsevier.com/retrieve/pii/S0304-3835(05)00390-3] Affected individuals develop the full range of cancers found in the general population, but the cancers arise unusually early in life. People with Bloom syndrome may be first diagnosed with cancer at about 25 years old.

Pathophysiology

Mutations in the "BLM" gene, which is a member of the DNA helicase family, are associated with Bloom syndrome. DNA helicases are enzymes that unwind the two spiral strands of a DNA molecule so that they can be copied. When a cell prepares to divide to form two cells, the chromosomes are duplicated so that each new cell will get a complete set of chromosomes; this replication process involves unwinding the DNA so that it can be copied. The BLM protein is important in maintaining the stability of the DNA during this process. Mutations in the "BLM" gene alter or reduce the BLM protein's DNA helicase activity, which causes errors in the copying process during replication. As a result, people with Bloom syndrome have a higher frequency of chromosome breakage and rearrangement than unaffected people. This increase in chromosome breakage and rearrangement leads to the signs and symptoms of Bloom syndrome. Another suggestion put forward is that individuals with Bloom syndrome overproduce the superoxide anion, whose volatility damages the chromosomes.

Bloom syndrome is inherited in an autosomal recessive fashion. Both parents must be carriers in order for a child to be affected. The carrier frequency in individuals of Eastern European ancestry is about 1/100. If both parents are carriers, there is a one in four, or 25%, chance with each pregnancy for an affected child. Genetic counseling and genetic testing is recommended for families who may be carriers of Bloom syndrome.

ee also

*Accelerated aging disease
*Bloom syndrome (gene)
*DNA repair
*Progeria

References

External links

* [http://www.bloomsconnect.org/ Blooms Connect - a forum by and for people with Bloom's Syndrome and their loved ones]
* [http://www.bloomssyndrome.org/ Bloom's Syndrome Foundation - devoted to medical & scientific research to discover a treatment or cure for Bloom's Syndrome]
* [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/DNArepair.html DNA Repair]
* [http://www.benbest.com/lifeext/aging.html#progeria Segmental Progeria]
* [http://gladwinmedical.blogspot.com/2006/07/blooms-syndrome-autosomal-recessive.html Article on Bloom's Syndrome]
*NLM|bloomsyndrome