National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Bloom syndrome


Other Names:
BS; Bloom-Torre-Machacek syndrome; BLM; BS; Bloom-Torre-Machacek syndrome; BLM; Growth deficiency, sun-sensitive, telangiectatic, hypo and hyperpigmented skin, predisposition to malignancy and chromosomal instability; BLS; Congenital Telangiectatic Erythema See More
Categories:
Bloom syndrome is a disorder characterized by a significantly increased risk of cancer and various other features. Signs and symptoms include short stature; sun-sensitive skin changes on the face, hands and/or arms; a high-pitched voice; and distinctive facial features including a long, narrow face, small lower jaw, large nose and prominent ears. Some affected individuals may also have learning disabilities; an increased risk of diabetes; chronic obstructive pulmonary disease (COPD); and recurrent infections of the upper respiratory tract, ears, and lungs during infancy. Cancers may include any of those found in the general population, but develop much earlier in life in affected individuals. It is caused by mutations in the BLM gene and is inherited in an autosomal recessive manner.[1] Treatment is generally symptomatic and supportive.
Last updated: 9/1/2011

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Abnormality of chromosome stability 0003220
Delayed skeletal maturation
Delayed bone maturation
Delayed skeletal development
[ more ] 		0002750
Diarrhea
Watery stool
0002014
Dolichocephaly
Long, narrow head
Tall and narrow skull
[ more ] 		0000268
Erythema 0010783
Facial telangiectasia in butterfly midface distribution 0005598
Intrauterine growth retardation
Prenatal growth deficiency
Prenatal growth retardation
[ more ] 		0001511
Malar flattening
Zygomatic flattening
0000272
Narrow face
Decreased breadth of face
Decreased width of face
[ more ] 		0000275
Postnatal growth retardation
Growth delay as children
0008897
Recurrent respiratory infections
Frequent respiratory infections
Multiple respiratory infections
respiratory infections, recurrent
Susceptibility to respiratory infections
[ more ] 		0002205
Short stature
Decreased body height
Small stature
[ more ] 		0004322
Sinusitis
Sinus inflammation
0000246
Spotty hyperpigmentation
Spotty increased pigmentation
0005585
30%-79% of people have these symptoms
Cutaneous photosensitivity
Photosensitive skin
Photosensitive skin rashes
Photosensitivity
Sensitivity to sunlight
Skin photosensitivity
Sun sensitivity
[ more ] 		0000992
High pitched voice 0001620
Hypoplasia of the zygomatic bone
Cheekbone underdevelopment
Decreased size of cheekbone
Underdevelopment of cheekbone
[ more ] 		0010669
Short nose
Decreased length of nose
Shortened nose
[ more ] 		0003196
5%-29% of people have these symptoms
Acute leukemia 0002488
Azoospermia
Absent sperm in semen
0000027
Decreased circulating IgA level 0002720
Decreased circulating IgG level 0004315
Decreased circulating total IgM 0002850
Decreased fertility in females
Reduced fertility in females
0000868
Finger syndactyly 0006101
Hand polydactyly
Extra finger
0001161
Hyperhidrosis
Excessive sweating
Increased sweating
Profuse sweating
Sweating
Sweating profusely
Sweating, increased
[ more ] 		0000975
Hypopigmented skin patches
Patchy loss of skin color
0001053
Ichthyosis 0008064
Intellectual disability, mild
Mental retardation, borderline-mild
Mild and nonprogressive mental retardation
Mild mental retardation
[ more ] 		0001256
Lymphoma
Cancer of lymphatic system
0002665
Microcephaly
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference
[ more ] 		0000252
Neoplasm of the gastrointestinal tract
Gastrointestinal tract tumor
GI tract tumor
[ more ] 		0007378
Protruding ear
Prominent ear
Prominent ears
[ more ] 		0000411
Reduced number of teeth
Decreased tooth count
0009804
Sacral dimple
Spinal dimple
0000960
Squamous cell carcinoma 0002860
Percent of people who have these symptoms is not available through HPO
Agenesis of maxillary lateral incisor 0000690
Autosomal recessive inheritance 0000007
Bronchiectasis
Permanent enlargement of the airways of the lungs
0002110
Cafe-au-lait spot 0000957
Chromosome breakage 0040012
Chronic lung disease 0006528
Clinodactyly of the 5th finger
Permanent curving of the pinkie finger
0004209
Cryptorchidism
Undescended testes
Undescended testis
[ more ] 		0000028
Hypertrichosis 0000998
Leukemia 0001909
Prominent nose
Big nose
Disproportionately large nose
Increased nasal size
Increased size of nose
Large nose
Pronounced nose
[ more ] 		0000448
Specific learning disability 0001328
Spotty hypopigmentation
Patchy hypopigmentation
Spotty decreased pigmentation
[ more ] 		0005590
Syndactyly
Webbed fingers or toes
0001159
Type II diabetes mellitus
Noninsulin-dependent diabetes
Type 2 diabetes
Type II diabetes
[ more ] 		0005978
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Last updated: 7/1/2020
Bloom syndrome is diagnosed by either cytogenetic analysis or mutation testing. Cytogenetic analysis is used to detect if there is an increased amount of sister chromatid exchange in cells. Genetic testing can reveal if a person has mutations in the BLM gene, which are known to cause Bloom Syndrome.[1] If an individual has a family history of Bloom syndrome, one of these two testing methods may be used to find out if the person has also inherited the condition. An unusually low birth weight and short height throughout childhood are suggestive of Bloom syndrome in an individual with an affected sibling.[2] For more information about the diagnosis of Bloom syndrome, please visit: http://www.ncbi.nlm.nih.gov/books/NBK1398/#bloom.Diagnosis
Last updated: 4/13/2012

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.
There is currently no cure for Bloom syndrome, so treatment is generally symptomatic and supportive. Because affected individuals are hypersensitive to DNA-damaging chemicals and ionizing radiation, standard cancer treatment plans often need to be adjusted for affected individuals. Changes may include reducing both the dosage and duration of the treatment; however, the cancers in affected individuals are often unusually responsive to treatment. The wide variety of types of cancer as well as the early development of tumors in affected individuals make life-long cancer surveillance significantly important. Additionally, it is recommended that individuals avoid sun exposure to the face, particularly in infancy and early childhood. Treatment of diabetes is typically the same as for individuals in the general population.[2]
Last updated: 9/1/2011

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
The differential diagnosis of Bloom syndrome includes Fanconi anemia, Silver-Russell syndrome, Rothmund-Thomson syndrome, ataxia-telangiectasia, and Nijmegen breakage syndrome. Three other disorders also may be of interest in a differential diagnosis. RECQ-mediated genome instability 1, RECQ-mediated genome instability 2, Microcephaly, growth restriction, & increased sister-chromatid exchange 2.
Visit the Orphanet disease page for more information.

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Bloom syndrome. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

Patient Registry

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Organizations Providing General Support

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • DermNet NZ is an online resource about skin diseases developed by the New Zealand Dermatological Society Incorporated. DermNet NZ provides information about this condition.
  • Genetics Home Reference (GHR) contains information on Bloom syndrome. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Bloom syndrome. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • I have Bloom syndrome and am wondering if I'm able to become pregnant. See answer

  • Can Bloom syndrome be detected before symptoms appear? See answer

  • My nephew and niece, ages 4 and 1, have been diagnosed with Bloom syndrome very recently. We, as a family, are passing through a lot of stress and would be highly obliged if you could let us know if there is any treatment or gene therapy which can be offered now or in the near future. Any help or leads would be highly appreciated. See answer


  1. Bloom syndrome. Genetics Home Reference. November 2010; http://ghr.nlm.nih.gov/condition/bloom-syndrome. Accessed 3/31/2014.
  2. Maureen M Sanz, James German. Bloom's syndrome. GeneReviews. March 28, 2013; http://www.ncbi.nlm.nih.gov/books/NBK1398/. Accessed 3/31/2014.