Bloom Syndrome

Gene : BLM

What is Bloom syndrome?

Bloom syndrome is an inherited disorder characterized by short stature, skin changes due to sun exposure, and increased risk of cancer. Other health problems may include gastroesophageal reflux, infections, chronic lung disease, diabetes, and infertility. Some individuals with Bloom syndrome have learning disabilities. People with Bloom syndrome remain much shorter and thinner than their other family members. They are also at higher risk than the general population to develop any of the cancers in the general population and are also at risk of being diagnosed with more than one cancer. Life expectancy varies depending on medical complications, but is often into adulthood. The most common cause of death is cancer. Bloom syndrome is caused by pathogenic variants in the BLM gene.

How is Bloom syndrome inherited?

Bloom syndrome is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant in the gene for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

What does it mean to be a carrier?

There are generally no signs or symptoms associated with being a carrier of Bloom Syndrome, , however it is unknown if Bloom syndrome carriers have an increased cancer risk of developing cancer. Carriers are at an increased risk of having a child with Bloom syndrome. Testing of reproductive partners, with consideration to their ethnicity, is recommended for carriers of Bloom syndrome.

How common is Bloom syndrome?

Bloom syndrome is a rare disorder in the general population. The disorder is much more frequent in the Ashkenazi Jewish population, occurring in 1 in 50,000 newborns.

Family References and Resources
Clinician References
What is Analyzed?
  • Full gene sequencing
Affected Systems




Increased Cancer Risk

Carrier Rates
Detection Rate
Carrier Frequency
Ashkenazi Jewish > 99% 1 in 140
General Population 87% 1 in 1756

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