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.
Key Data
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Synonym | |
Genes | Robertsonian translocation 15;21 Ring chromosome 21 syndrome |
Gene product | Not applicable |
Funktion | Not applicable |
Erbgang | 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. |
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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
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.
Therapeutic Considerations
It is invariably helpful to have a discussion with the ALL principal investigator.
Surveillance Recommendations
Surveillance Recommendations
Since Robertsonian translocation 15;21 and ring chromosome 21 are very rare genetic alterations, there is not yet sufficient data available to provide standardized recommendations for early detection.
As with other leukemia predisposition syndromes, the following examinations should be conducted on a regular basis:
Additional Information
Open Clinical Trials / Registries
Support Groups
Unfortunately, we are as yet unaware of any existing support groups for patients with Robertsonian translocation 15;21 or ring chromosome 21 syndrome. We will add new information as it becomes available.