TAR syndrome

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Other Names:

Thrombocytopenia absent radius syndrome; Absent radii and thrombocytopenia; Thrombocytopenia absent radii

Categories:

Blood Diseases; Congenital and Genetic Diseases; Musculoskeletal Diseases

Summary Summary

TAR syndrome is characterized by the absence of a bone called the radius in each forearm, short stature, and thrombocytopenia. The thrombocytopenia often appears first in infancy but becomes less severe or returns to normal over time. Infants and young children are particularly vulnerable to episodes of severe bleeding which may occur in the brain and other organs. Children who survive this period and do not have damaging bleeding in the brain usually have a normal life expectancy and normal intellectual development. Other signs and symptoms vary but may include heart defects, kidney defects, and other skeletal abnormalities. About half of people with TAR syndrome also have difficulty digesting cow's milk. TAR syndrome is thought be caused by a deletion of genes on chromosome 1q21.1 in concert with another genetic change that has yet to be identified. Click here to see a diagram of chromosome 1.^[1]

Last updated: 3/26/2012

Symptoms Symptoms

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 coagulation		0001928
Absent radius	Missing outer large bone of forearm	0003974
Aplasia/Hypoplasia of the ulna	Absence/underdevelopment of inner forearm bone	0006495
Thrombocytopenia	Low platelet count	0001873
30%-79% of people have these symptoms
Adducted thumb	Inward turned thumb	0001181
Anemia	Low number of red blood cells or hemoglobin	0001903
Aplasia/hypoplasia of the humerus	Absent/small long bone in upper arm Absent/underdeveloped long bone in upper arm [ more ]	0006507
Aplasia/Hypoplasia of the patella	Absent/small kneecap Absent/underdeveloped kneecap [ more ]	0006498
Broad forehead	Increased width of the forehead Wide forehead [ more ]	0000337
Broad thumb	Broad thumbs Wide/broad thumb [ more ]	0011304
Clinodactyly of the 5th finger	Permanent curving of the pinkie finger	0004209
Cow milk allergy	Milk allergy	0100327
Coxa valga		0002673
Eosinophilia	High blood eosinophil count	0001880
Genu varum	Outward bow-leggedness Outward bowing at knees [ more ]	0002970
High forehead		0000348
Hip dislocation	Dislocated hips Dislocation of hip [ more ]	0002827
Low-set, posteriorly rotated ears		0000368
Patellar aplasia	Absent kneecap	0006443
Patellar dislocation	Dislocated kneecap	0002999
Tibial torsion		0100694
5%-29% of people have these symptoms
Abnormal cardiac septum morphology		0001671
Abnormal shoulder morphology	Abnormality of the shoulder	0003043
Aplasia of the uterus	Absent uterus uterus absent [ more ]	0000151
Axial malrotation of the kidney		0004717
Carpal bone hypoplasia	Small carpal bones Small carpals [ more ]	0001498
Cavum septum pellucidum		0002389
Cerebellar hypoplasia	Small cerebellum Underdeveloped cerebellum [ more ]	0001321
Cervical ribs		0000891
Cleft palate	Cleft roof of mouth	0000175
Coarctation of aorta	Narrowing of aorta Narrowing of the aorta [ more ]	0001680
Delayed CNS myelination		0002188
Edema of the dorsum of feet		0012098
Edema of the dorsum of hands		0007514
Fibular aplasia	Absent calf bone	0002990
Finger syndactyly		0006101
Fused cervical vertebrae	Fused neck	0002949
Global developmental delay		0001263
Hepatosplenomegaly	Enlarged liver and spleen	0001433
Horseshoe kidney	Horseshoe kidneys	0000085
Lateral clavicle hook	Hook-shaped collarbone	0000895
Malar flattening	Zygomatic flattening	0000272
Micrognathia	Little lower jaw Small jaw Small lower jaw [ more ]	0000347
Nevus flammeus of the forehead	Port-wine stain on forehead	0007413
Phocomelia		0009829
Ptosis	Drooping upper eyelid	0000508
Scoliosis		0002650
Sensorineural hearing impairment		0000407
Short phalanx of finger	Short finger bones	0009803
Strabismus	Cross-eyed Squint Squint eyes [ more ]	0000486
Talipes equinovarus	Club feet Club foot Clubfeet Clubfoot [ more ]	0001762
Tetralogy of Fallot		0001636
1%-4% of people have these symptoms
Bilateral radial aplasia		0004977
Death in infancy	Infantile death Lethal in infancy [ more ]	0001522
Short stature	Decreased body height Small stature [ more ]	0004322
Ventricular septal defect	Hole in heart wall separating two lower heart chambers	0001629
Percent of people who have these symptoms is not available through HPO
Anteverted nares	Nasal tip, upturned Upturned nasal tip Upturned nose Upturned nostrils [ more ]	0000463
Atrial septal defect	An opening in the wall separating the top two chambers of the heart Hole in heart wall separating two upper heart chambers [ more ]	0001631
Autosomal recessive inheritance		0000007
Brachycephaly	Short and broad skull	0000248
Carpal synostosis		0009702
Decreased circulating antibody level		0004313
Intellectual disability	Mental deficiency Mental retardation Mental retardation, nonspecific Mental-retardation [ more ]	0001249
Meckel diverticulum		0002245
Motor delay		0001270
Pancreatic cysts		0001737
Seborrheic dermatitis		0001051
Seizure		0001250
Shoulder muscle hypoplasia	Underdeveloped shoulder muscle	0008952
Spina bifida		0002414

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Do you have more information about symptoms of this disease? We want to hear from you.

Last updated: 1/1/2021

Do you have updated information on this disease? We want to hear from you.

Diagnosis Diagnosis

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

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.
Orphanet lists international laboratories offering diagnostic testing for this condition.

Treatment Treatment

The resources below provide information about treatment options for this condition. If you have questions about which treatment is right for you, talk to your healthcare professional.

Management Guidelines

Project OrphanAnesthesia is a project whose aim is to create peer-reviewed, readily accessible guidelines for patients with rare diseases and for the anesthesiologists caring for them. The project is a collaborative effort of the German Society of Anesthesiology and Intensive Care, Orphanet, the European Society of Pediatric Anesthesia, anesthetists and rare disease experts with the aim to contribute to patient safety.

Prognosis Prognosis

The first two years of life are the most critical in TAR syndrome.^[2] During this time, children frequently develop life-threatening bleeding episodes due to extremely low platelet levels (thrombocytopenia). These episodes decrease with age, and platelet counts are usually normal by the time a child goes to school.^[2] Many individuals with TAR syndrome are allergic to cow's milk, which can also exacerbate the symptoms of thrombocytopenia.^[3] Intellectual development is usually not affected by TAR syndrome, though some individuals have intellectual disability due to complications from bleeding within the brain.^[2] People with TAR syndrome may be at increased risk of developing acute leukemia during childhood or adulthood.^[2]

Last updated: 2/19/2014

Find a Specialist Find a Specialist

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

The American College of Surgeons has a tool for learning more about various subspecialties and for locating local surgeons. Click on the link to view this search tool.
The American Society for Surgery of the Hand has a tool for locating hand surgeons. Click on the link to view this search tool.
To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.

Related Diseases Related Diseases

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 main differential diagnoses include Holt-Oram syndrome, Roberts syndrome, Fanconi anemia, thalidomide embryopathy and RAPADILINO syndrome (see these terms). Visit the Orphanet disease page for more information.

Research Research

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.

Patient Registry

A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with TAR syndrome. The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information. Learn more about registries.

Registries for TAR syndrome:
The Pediatric Myelodysplastic Syndrome (MDS) and Bone Marrow Failure (BMF) Registry
Inherited Bone Marrow Failure Syndrome Study (IBMFS)

Organizations Organizations

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

Birth Defect Research for Children, Inc.
976 Lake Baldwin Lane, Suite 104
Orlando, FL 32814
Telephone: +1-407-895-0802
E-mail: staff@birthdefects.org
Website: https://www.birthdefects.org/
Platelet Disorder Support Association
8751 Brecksville Road
Suite 150
Cleveland, OH 44141
Toll-free: 87-PLATELET (1-877-528-3538)
Telephone: 440-746-9003
Fax: 844-270-1277
E-mail: pdsa@pdsa.org
Website: http://www.pdsa.org/
TAR Syndrome Support Group
United Kingdom
E-mail: Susyedwards@hotmail.co.uk
Website: http://www.ivh.se/TAR/

Social Networking Websites

RareConnect is an online social network for patients and families to connect with one another and share their experience living with a rare disease. The project is a joint collaboration between EURORDIS (European Rare Disease Organisation) and NORD (National Organization for Rare Disorders). Click on the link above to view the community for limb differences.

Do you know of an organization? We want to hear from you.

Learn More Learn More

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

The Children’s Hospital Boston has a information page on congenital limb defects. Click on the link above to view this information page.
Genetics Home Reference (GHR) contains information on TAR syndrome. This website is maintained by the National Library of Medicine.
The National Cancer Institute provides the most current information on cancer for patients, health professionals, and the general public.

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 TAR syndrome. Click on the link to view a sample search on this topic.

GARD Answers GARD Answers

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

Has TAR syndrome been associated with white cell abnormalities in the bone marrow? What about cancer? See answer

Have a question? Contact a GARD Information Specialist.

References References

Thrombocytopenia-absent radius syndrome. Genetics Home Reference. October 2012; http://ghr.nlm.nih.gov/condition=thrombocytopeniaabsentradiussyndrome.
John K Wu. Thrombocytopenia-absent radius syndrome. Medscape Reference. April 16, 2012; http://reference.medscape.com/article/959262-overview.
Toriello, HV. Thrombocytopenia absent radius syndrome. GeneReviews. June 28, 2012; http://www.ncbi.nlm.nih.gov/books/NBK23758/.

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