What is Bloom syndrome?
Bloom Syndrome is also known as Bloom-Torre-Machacek syndrome.
It is an autosomal recessive disorder that is characterized by short stature, a rash that develops on exposure to the sun and an increased risk of developing cancer.
The skin rash that develops is often a butterfly-shaped patch of reddened skin across the nose and cheeks.
The rash can also develop in other areas of the body that get exposed to the sun.
People with Bloom syndrome also have:
- High-pitched voice
- Long and narrow face
- Small lower jaw and
- Prominent nose and ears
Who is affected by Bloom syndrome?
Bloom syndrome is a rare disease and only about 275 cases have been reported so far.
It can be seen in many ethnic groups but is more common is the Ashkenazi Jews, who have Polish or Ukrainian ancestry.
They also have a high carrier frequency with 1 in every 100 people being a carrier of the mutation.
What is the cause of bloom syndrome?
Bloom syndrome is an autosomal recessive trait.
The gene responsible for this syndrome has been traced to band 26.1 on the q arm of chromosome 15.
This part is responsible for the production of the protein BLM.
A single mutation of the gene, known as BLMAsh is responsible for most Bloom Syndrome cases among the Ashkenazi Jews.
Protein RecQ helicase is controlled by the gene for Bloom syndrome and is involved in cell repair, cell division, and cell death.
The condition is presumed to result from a defect in the cell’s DNA repair mechanism.
What is the treatment for Bloom syndrome?
Currently, there is no treatment for Bloom syndrome.
The treatments provided today are only symptomatic and supportive.
Affected individuals are often hypersensitive to DNA damaging chemicals and radiation therapies that are done for cancer treatments.
Hence, these treatments need to be modified for those suffering from Bloom syndrome.
People with the condition, especially infants and kids, are advised to avoid sun exposure to the face and back.
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Treatment of Manifestations
Since the exposure to the sun leads to the appearance of a butterfly-shaped rash, skin protection is an important part of the treatment of the symptoms.
This includes coverage of exposed skin and the use of broad-spectrum sunscreen of at least 30 SPF.
Another clinical manifestation of Bloom syndrome is a short height or stature.
So, many clinicians promote hormone treatment to improve linear growth.
However, many clinicians caution against this due to the early onset of cancer in some children who were treated in the past.
Other treatment measures include insulin resistance seen in type 2 diabetes and reduced intensity or dose of chemotherapy dosage.
People with recurrent infections and defects in humoral immunity are treated with gamma globulin infusions that help decrease the frequency or severity of the infection.
Can Bloom syndrome be prevented?
Bloom syndrome today cannot be prevented as it is a genetic disorder.
But, it is advisable to undergo a genetic test in case there seems to be an increased risk of developing the syndrome.
Expecting parents can undergo a prenatal genetic test to diagnose the genetic profile of the unborn child for bloom syndrome.
If there is a family history of the condition, genetic counseling is helpful to plan a child.
There is a lot of research currently underway to find ways to prevent and treat the syndrome.
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How prevalent is Bloom's syndrome?
Bloom syndrome is a very rare disease but its exact frequency is unknown to date.
Every 1 in 48,000 Ashkenazi Jews is affected by the disease. About 1.3rd of the people with the disease are of Ashkenazi Jewish descent.
How is Bloom syndrome inherited?
Bloom syndrome is inherited in an autosomal recessive manner.
This means that one needs to have two positive alleles of the gene to develop the syndrome.
If someone has one allele for the syndrome, it means that the person is a carrier of the disease.
Two carrier parents have a 25% chance to give birth to a child with Bloom Syndrome.
How does Bloom syndrome affect the body?
Bloom syndrome is evident right from the time a child is born.
They are exceptionally small in size and fail to grow up normally.
They fail to reach even 5 ft in height in adulthood.
Other features of Bloom syndrome include:
Skin Effects
- Pigmentation on the sun-exposed areas.
- Crusting and bleeding of lips
- Skin problems get aggravated on exposure to the sun
- Butterfly distribution and redness of the skin of the face.
Facial skeleton and body features:
- Bird-like face with a narrow, prominent nose
- Abnormally long limbs(in comparison with the body)
- Large protruding ears
- High pitched voice
- Decreased IgA and IgM
- Increased susceptibility to cancer like skin cancer, leukemia, and solid organ cancer
- Infertility is seen in both men and women
What is the BLM gene?
The BLM gene mutation is responsible for the development of Bloom Syndrome.
The BLM gene is responsible for giving instructions for the synthesis of a protein known as RecQ helicases.
These helicases attach to the DNA and unwind or uncoil the two spiral strands, which are needed for the various processes and cell functions.
Since these proteins help in maintaining the structure of the DNA, they are called as ‘caretakers of the genome’.
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Surveillance for individuals with bloom syndrome
Patients with Bloom syndrome are at an increased risk of developing different types of cancers.
To monitor such patients, an abdominal ultrasound is done every 3 months until the child turns 8 years to detect or diagnose a Wilms tumor.
The family is screened and educated about the signs and symptoms of lymphomas and leukemia.
Until the age of 13 years, a full-body MRI is done once in every 1-2 years and an annual colonoscopy after the child turns 10.
If a girl is affected, an annual breast MRI is done once she turns 18 years of age.
Other regular blood investigations are done regularly to keep parameters under check.
Annual TSH serum level tests are done from the age of 10 yrs. Annual lipid profile tests are started at 10 years of age.
Some facts about bloom syndrome
People suffering from Bloom Syndrome have high instability in their chromosomes. Due to this:
- They have a short stature
- Increased tendency to develop diabetes
- Infertility in both men and women
- Shortened life span with an average of up to 24 years
- Increased risk of developing cancer in early life
Bloom syndrome and the risk of cancer
Since the syndrome is due to an instability of the DNA, it goes without saying that this instability is one of the prime causes for the development of cancer in these individuals.
Individuals with Bloom syndrome have an increased susceptibility to various types of cancers and about 50% of the people will develop cancers like leukemias and lymphomas.
Bloom syndrome and risk of cystic fibrosis
People with an Ashkenazi Jewish ancestry are carriers of certain disease conditions including Bloom Syndrome and Cystic Fibrosis.
This group of people has a 20-25% chance of developing either of these two or other genetic conditions like Gaucher’s disease, Tay-Sach disease, etc.
However, there is no direct connection between the two diseases.
Bloom syndrome and chronic obstructive pulmonary disease risk
Individuals with Bloom Syndrome have an increased risk of developing systemic conditions like diabetes, a chronic obstructive pulmonary disorder, immune system-related conditions, and recurrent upper respiratory tract infections.
Xcode Life’s Carrier Status Report provides information on inherited conditions based on the genetic variants for more than 275 such traits.
References:
- https://ghr.nlm.nih.gov/condition/bloom-syndrome
- https://rarediseases.org/rare-diseases/bloom-syndrome/
- https://www.ncbi.nlm.nih.gov/books/NBK1398/
- https://www.ncbi.nlm.nih.gov/books/NBK1398/
- https://ghr.nlm.nih.gov/condition/bloom-syndrome
- https://ghr.nlm.nih.gov/gene/BLM
- https://www.ncbi.nlm.nih.gov/books/NBK1398/
- https://www.ncbi.nlm.nih.gov/medgen/2685
