Ring chromosome 15
Ring chromosome 15 | |
---|---|
Other names | Ring chromosome 15 syndrome, Ring 15 |
Supportive | |
Frequency | Rare |
Ring chromosome 15 (sometimes denoted as r15) is a condition that arises when
All chromosomes have the capacity to form ring chromosomes. The symptoms and severity largely depend on the amount and location of the genetic information lost.[2] If the ends of the chromosome fuse with no loss of genetic material, the individual retains the normal phenotype with relatively slight differences. However, evidence suggests that when there is deletion of genetic information at the distal unstable ends where the subtelomeric structures fuse, syndromes associated with that particular chromosome arise.[3]
Treatment for ring chromosome 15 predominantly targets the management of these symptoms rather than the chromosome ring itself.
Presentation
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Cafe_au_lait.jpg/220px-Cafe_au_lait.jpg)
Reported cases are few in number, and the phenotype expression for ring chromosome 15 syndrome occurs over a wide spectrum.[4][5][6] As well, the cells of patients can have different levels of mosaicism, creating even greater variation in the presence and severity of expression.[2] Thus, while a precise genotype–phenotype association hasn't been fully established,[2] common features associated with the syndrome have been determined.
An examination of 25 cases showed that
Research into ring chromosome 15 generally attempts to elucidate the causes of symptoms. For example, growth retardation may be caused by terminal deletion of the region 15q26,
Mechanism
The human body stores its genetic information in
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/Telomere.png/220px-Telomere.png)
There are two proposed mechanisms of forming the ring chromosome. One suggests that chromosome 15 undergoes distortion on both p and q arms prior to the fusion of two broken arms, resulting in great loss of genetic materials. Therefore, the patients of this type of ring chromosome 15 display severe clinical features.[12]
The other proposed mechanism suggests the direct fusion of two telomeres without losing any of the telomeric and subtelomeric sequences. Consequently, most of the genetic material is conserved and symptoms are expressed in a milder form, making diagnosis more difficult.[13]
Diagnosis
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/Diaphragm_hernia2.jpg/220px-Diaphragm_hernia2.jpg)
In most cases, postnatal diagnosis is done and up to 2011, only four cases are reported via prenatal diagnosis.[3] Congenital diaphragmatic hernia and
Postnatal diagnosis
Patients could be considered to have ring chromosome 15 if they are found with: growth deficiency,
Management
Treatment of the disease is based on alleviating symptoms,[1] commonly including physiotherapy, occupational therapy, and speech and language therapy.[14] In addition, case reports have found that recombinant human growth hormone treatment may be beneficial for improving the growth velocity of patients with short stature.[3][4][15]
Epidemiology
Ring chromosome syndromes are rare congenital disorders that are likely to occur in both males and females, and the symptoms can be observed from birth since it arises during the embryonic stage. All races and ethnicities are prone to the disorders and the risk can be higher if the parents are carriers since it is genetically inherited.[citation needed]
Any of the 23 pairs of chromosomes can be ringed, and a recent study conducted by the 'Human Ring Chromosome Registry' in China revealed that the more frequent forms of ring chromosomes reported were 13, 15, 18, and 22.[16]
History
Ring chromosome 15 is an uncommon genetic disorder first noted by Dr. Petrea Jacobsen in 1966.[17] As of 2005, less than 50 cases have been reported.[2]
References
- ^ a b "Ring chromosome 15 | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Retrieved 2019-04-11.
- ^ S2CID 24115238.
- ^ a b c d Xu, F; Zou, CC; Liang, L; Huang, XM; Shao, YN (2011). "Ring Chromosome 15 Syndrome:Case Report and Literature Review". HK J Paediatr. New Series: 175–179.
- ^ PMID 3278612.
- PMID 1849352.
- PMID 7545237.
- S2CID 35310940.
- ^ "Orphanet: Growth%20delay%20due%20to%20insulin like%20growth%20factor%20I%20resistance". www.orpha.net. Retrieved 23 April 2020.
- PMID 7789178.
- ^ Reference, Genetics Home. "What is a chromosome?". Genetics Home Reference. Retrieved 2019-04-11.
- ^ "Definition of Long arm of a chromosome". MedicineNet. Archived from the original on 2020-06-21. Retrieved 2019-04-11.
- S2CID 1596675.
- S2CID 23582495.
- ^ Morava, E. (2005). "Ring 15" (PDF). Unique. Archived from the original (PDF) on 5 December 2017.
- PMID 34747577.
- PMID 29492108.
- ISSN 0018-0661.