Skip Navigation
About   Site Map   Contact Us
A service of the U.S. National Library of Medicine®
Printer-friendly version
Bloom syndrome
 Quick links to this topic
 Health information
 Information pages
 For patients and families
 Clinical summary
 DNA test labs
 Teaching cases
 Research studies
 Recent literature
 Medical and science texts
 Genetic disorder catalog

Bloom syndrome

Reviewed July 2006

What is Bloom syndrome?

Bloom syndrome is an inherited disorder characterized by a high frequency of breaks and rearrangements in an affected person's chromosomes. People with Bloom syndrome are much smaller than average, and often have a high-pitched voice and characteristic facial features including a long, narrow face; small lower jaw; and prominent nose and ears. They tend to 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 intellectual disabilities, 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 (infertile). Women with the disorder generally experience menopause earlier than usual.

Chromosome instability in Bloom syndrome results in a high risk of cancer in affected individuals. 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.

How common is Bloom syndrome?

Bloom syndrome is a very rare disorder in most populations, and its overall frequency is unknown. It is more common in people of Central and Eastern European (Ashkenazi) Jewish background, among whom 1 in 48,000 are affected. Approximately one third of people with Bloom syndrome are of Ashkenazi Jewish descent.

What genes are related to Bloom syndrome?

Mutations in the BLM gene cause Bloom syndrome.

The BLM gene provides instructions for producing a protein called the Bloom (BLM) syndrome protein, which is a member of the DNA helicase family. 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 (replicated) so that each new cell will get a complete set of chromosomes. The 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.

Read more about the BLM gene.

How do people inherit Bloom syndrome?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about treatment for Bloom syndrome?

These resources address the management of Bloom syndrome and may include treatment providers.

You might also find information on treatment of Bloom syndrome in Educational resources and Patient support.

Where can I find additional information about Bloom syndrome?

You may find the following resources about Bloom syndrome helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for Bloom syndrome?

  • Bloom-Torre-Machacek Syndrome

What if I still have specific questions about Bloom syndrome?

Where can I find general information about genetic conditions?

What glossary definitions help with understanding Bloom syndrome?

Ashkenazi Jewish ; autosomal ; autosomal recessive ; cancer ; cell ; chromosome ; chronic ; deficiency ; diabetes ; dilated ; DNA ; enzyme ; gene ; helicase ; infection ; infertile ; menopause ; molecule ; mutation ; pigmentation ; pneumonia ; population ; protein ; rearrangement ; recessive ; sign ; sperm ; symptom ; syndrome

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

References (12 links)


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.

Reviewed: July 2006
Published: January 23, 2009