Robertsonian Translocation 15;21, Ring Chromosome 21 – Definition
Robertsonian translocation 15;21 and ring chromosome 21 syndrome are very rare chromosomal aberrations that result in a greatly increased risk of developing ALL, where the ALL variant is a specific subtype that exhibits intrachromosomal amplification of a copy of chromosome 21 and is thus referred to as iAMP21-ALL. Any association with other forms of ALL or other tumor diseases is currently not known.
Synonym:
Gene:
Robertsonian translocation 15;21
Ring chromosome 21 syndrome
Gene product:
not applicable
Function:
not applicable
Pattern of inheritance:
not applicable
Prevalence:
The incidence of Robertsonian translocation 15;21 ranges between 1:100.000-1:200.000 and 1:20.000 infants.
The incidence of ring chromosome 21 syndrome is not known.
Genotype-phenotype correlation:
The only association of Robertsonian translocation 15;21 known so far is with iAMP21-ALL.
Penetrance:
Unknown
The risk of developing iAMP21-ALL is around 2700 times higher compared to the general population.
Robertsonian Translocation 15;21, Ring Chromosome 21 – Diagnosis
Genetic Diagnostics
The diagnosis of Robertsonian translocation 15;21 is confirmed by the detection of pericentric fusion of the two acrocentric chromosomes 15 and 21 in the chromosome analysis or fluorescence in situ hybridization (FISH). Evidence of ring chromosome 21 can be confirmed using this method as well.
Differential Diagnoses
- ALL with a different genetic cause
Clinical Presentation
Robertsonian translocation 15;21 can present itself clinically in the development of iAMP21-ALL. This specific form of ALL exhibits intrachromosomal amplification of a copy of chromosome 21. It occurs on average 9 years later than the other subtypes of pediatric ALL (which are detected on average between 2-5 years of age). In addition, it is also characterized by a low leukocyte count. The risk of developing iAMP21-ALL is around 2700 times higher compared to the general population.
The presence of ring chromosome 21, is also associated with an increased risk of developing iAMP21-ALL.
Special Features of Treatment
It is invariably helpful to have a discussion with the ALL principal investigator.
Diagnosis of Robertsonian Translocation 15;21, Ring Chromosome 21- What's Next?
Once diagnosed, it is recommended that a cancer predisposition specialist manage the patient. The following section explains whether cancer screening tests or other measures are necessary and how they should be performed. Some additional information, including links to support groups, is also included at the end of this page.
Diagnosis of Robertsonian Translocation 15;21, Ring Chromosome 21- What's Next?
Once diagnosed, it is recommended that a cancer predisposition specialist manage the patient. The following section explains whether cancer screening tests or other measures are necessary and how they should be performed. Some additional information, including links to support groups, is also included at the end of this page.
Recommendations for Early Detection in Your Patients
Since Robertsonian translocation 15;21 and ring chromosome 21 are very rare genetic alterations, sufficient data are not yet available to provide standardized recommendations for early detection.
As with other leukemia predisposition syndromes, the following examinations should be conducted regularly:
- Clinical examinations
- Complete blood count once a year
- Bone marrow puncture only with unstable blood values / clinically suspected leukemia
Robertsonian Translocation 15;21, Ring Chromosome 21 – Further Information
Open Clinical Trials/ Registries
Additional Resources
Unfortunately, we are currently not aware of any support groups for patients with Robertsonian Translocation 15;21, Ring Chromosome 21 syndrome. New information will be added as soon as it becomes available.
