What is Bloom Syndrome ?

What is Bloom syndrome?

• Bloom syndrome is a rare autosomal recessive chromosomal disorder, also known as Bloom-Torre-Machacek syndrome, and congenital telangiectatic erythema. It was discovered by dermatologist Dr. David Bloom in 1954

Diagnosis

• To find out if a a patient has Bloom Syndrome, the doctor performs a procedure in which he demonstrates the increase frequency of sister-chromatid exchanges' (SCEs) in cultured cells of any type
• Also the syndrome can be diagnosed by confirming the molecular genetic analysis of the BLM gene. This BLM gene is mutates in Bsyn
• This is done though molecular DNA Testing

What happens in the molecular level?

• Mutation in the BLM gene causes bloom syndrome. The BLM gene provides instructions for making a member of a protein family called RecQ hellicases
• Hellicases are enzymes that bind to DNA and temporarily unwind the double helix of the DNA molecule. This unwinding is necessary for replicating DNA for cell division
• When a cell prepares to divide into two cells, the DNA that makes up the chromosomes is copied so that each new cell will get a complete cell of chromosomes. This copies DNA from each chromosome is arranged into two identical structure called sister chromatids. Sister chromatids exchange small sections of DNA during the early stages of cell division. With the help of its partner proteins, BLM suppresses sister chromatids exchanges and helps maintain DNA stability during the coping process. 

What goes wrong in this process with the disease?  

• BLM gene mutations prevent the BLM protein from performing its function in maintaining genomic stability.
• As a result of the BLM protein activity, the frequency of sister chromatids exchange increase about ten times what it should be. This is an indicator of chromosomal instability
• This chromosal instability causes that cells cannot perform normal cell activities and causes the health problems associated with this condition

Symptoms

·     Exterior level:

§  Reddening in the skin in butterfly shape (face rash) shortly after first exposure to sun

§  Low birth weight and length

§  High pitched voice

§  Distinctive facial features; long narrow face, small lower jaw, a large nose, and prominent ear

§  Short stature (height) less than five feet

     Molecular level:

§  Dilated blood vessels

§  Learning disabilities

§  Increased risk of diabetes

§  Chronic obstructive pulmonary disease

§  Recurrent infection of the upper respiratory track, ears and lungs

§  Men do not produce sperms

§  Women have reduced fertility and experience menopause earlier than usual

Affected People

• Both parents have to be carriers for the child to inherit the disease

§  In other words in an autosomal recessive pattern

§  If both parents are carriers, there is a 25% chance that the child will be born with bloom syndrome

•       It Affects woman as well as men
•       It is detected during infancy or early childhood
•       Usually people do not live passed 30
•       Common for people with Jewish background

Autosomal disease

Autosomal disease:  Refers to any of the chromosomes other than the sex-determining chromosomes (i.e., the X and Y) or the genes on these chromosomes

Autosomal recessive: Describes a trait or disorder requiring the presence of two copies of a gene mutation at a particular locus in order to express observable phenotype; specifically refers to genes on one of the 22 pairs of autosomes (non-sex chromosomes)

What is affected?

•      metabolic disease
•      Affected: organs

§  Reproductive organs (sperm, and egg)

§  Lungs (chronic obstruction pulmonary disease) COPD

§  Increase risk of cancer and diabetes

Consequences

• People with bloom syndrome have hard time going out in public

§  Embarrassing face rash

§  Can not have a lot of exposure to sun

§  žLungs are affected meaning that people with bloom syndrome can not perform  athletic activities or cardiovascular exercise

• Diabetes affects the eyes, all circulatory system organs, kidneys, nerves, and digestive system.

Treatments

• There is no treatment for Bloom’s syndrome
• Preventative measures such as increased surveillance for cancer and decreased exposure to sunlight and X-rays should be taken
• Bone marrow transplant is a possibility

Were is it most common?

•      The disorder is more common in people from Central and Eastern Europe
•      The Ashkenazi Jewish people have a 1 in 50,000 chance to have bloom syndrome
•       Approximately 1/3 of people with Bloom syndrome are of Ashkenazi Jewish descent

References

German, J; M.D. (2002, January 3). Bloom’s syndrome a descriptive summary prepared by the bloom’s syndrome registry for registered persons and their families. Retrieved from http://www.bloomssyndrome.org/bloomssyndrome.htm

   žSanz , M; PhD . (2006, March 22). National Institute of Health: Bloom's syndrome . Retrieved from http://www.ncbi.nlm.nih.gov/books/NBK1398

     U.S Library of Medicine, Initials. (2010, November 20). Genetics home reference: bloom’s syndrome. Retrieved from http://ghr.nlm.nih.gov/condition/bloom-syndrome