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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Medical Genetics

Introduction to Ring Chromosome 13 Syndrome

At a Glance

Ring Chromosome 13 Syndrome is a rare, random genetic condition where the ends of chromosome 13 break and fuse into a circle. Symptoms and life expectancy vary widely based on how much genetic material was lost during the break and how the ring chromosome behaves during cell division.

Receiving a diagnosis of Ring Chromosome 13 Syndrome for your child can feel overwhelming, but it is important to understand that this is a de novo (new) genetic accident [1]. It is not caused by anything you did or did not do before or during pregnancy. This condition occurs when the two ends of chromosome 13 break and fuse together to form a circle or “ring” [2].

How the Ring Forms

In a typical cell, chromosome 13 is a straight line. The ring shape forms through a process of breaking and repair:

  1. Breakage: Double-strand breaks occur at both ends (the “p” and “q” arms) of the chromosome [2].
  2. Loss: The small pieces of genetic material at the very tips are usually lost during this process [2][3].
  3. Fusion: The “sticky” broken ends of the remaining chromosome fuse together into a circular shape [2].

The clinical impact of the syndrome is largely determined by how much genetic material was lost when the ends broke off [3][4]. If the breaks happened near the very tips, the child might have a very mild or even typical appearance; if the breaks occurred further down the chromosome, more vital instructions (genes) are missing, leading to more significant medical challenges [5][6].

Understanding Dynamic Mosaicism

One of the unique features of ring chromosomes is their instability, often called dynamic mosaicism [7][8].

Chromosomes must copy themselves and divide perfectly every time a cell splits. Because of its circular shape, a ring chromosome can get tangled or lost during this cell division [7]. This leads to different groups of cells (cell lines) within the same child:

  • Ring Cells: Some cells contain the ring chromosome.
  • Monosomy Cells: Some cells may lose the ring entirely, leaving them with only one copy of chromosome 13 [7][8].
  • Rearranged Cells: Some cells may have rings that have doubled in size or changed shape [7].

This internal mixture of cell types is why two children with the exact same missing genes can have very different symptoms [7][9].

Prognosis and Life Expectancy

Ring Chromosome 13 is a very rare condition [10]. Because the amount of lost material and the degree of mosaicism vary so much, there is no single established life expectancy [6].

Prognosis depends heavily on whether a child has severe congenital malformations [11]. Children with milder features and fewer organ malformations can live into adulthood and experience meaningful lives, while those with severe structural differences (like complex heart defects or severe brain malformations) may face life-limiting medical complications early in life [6][12].

It is important to remember that while some presentations are severe, others are much milder [6]. Your child’s medical team will use specialized tests like microarray or FISH to map exactly which genes are involved and create a personalized care plan [13][4].

Common questions in this guide

How does a ring chromosome 13 form?
A ring chromosome forms when both ends of chromosome 13 break off and the remaining sticky ends fuse together into a circle. The genetic material at the very tips of the chromosome is usually lost during this breakage process.
Did I cause my child's Ring Chromosome 13 Syndrome?
No, Ring Chromosome 13 is a de novo genetic accident, meaning it is a new, random occurrence. It is not caused by anything you did or did not do before or during your pregnancy.
What is dynamic mosaicism?
Dynamic mosaicism refers to the instability of the ring chromosome during cell division. Because of its circular shape, the ring can get lost or tangled, resulting in a mixture of different cell types in the body. This internal mixture is why symptoms can vary so much from child to child.
What is the life expectancy for a child with Ring Chromosome 13 Syndrome?
Life expectancy varies greatly depending on how much genetic material was lost and the presence of severe structural differences. Children with milder features can live into adulthood, while those with complex heart or brain malformations may face life-limiting medical complications early in life.
Why does my child need screening for retinoblastoma?
When the chromosome breaks to form the ring, vital instructions like the RB1 gene can be lost. If this specific gene is missing, your child will need regular monitoring to check for a type of eye tumor called retinoblastoma.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What are the specific 'breakpoints' on my child's chromosome 13, and which genes were lost during the ring formation?
  2. 2.Does the deletion include the RB1 gene, and does my child need regular screening for retinoblastoma?
  3. 3.What percentage of cells in the karyotype show the ring chromosome versus other cell lines (like monosomy 13)?
  4. 4.Based on the specific genetic material lost, what are the most important developmental or medical screenings we should prioritize right now?
  5. 5.Are there secondary rearrangements or instability in the ring that we should be aware of for future health monitoring?

Questions For You

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References

References (13)
  1. 1

    13q deletion syndrome resulting from balanced chromosomal rearrangement in father: the significance of parental karyotyping.

    Dittner-Moormann S, Reschke M, Biewald E, et al.

    Molecular cytogenetics 2020; (13()):31 doi:10.1186/s13039-020-00500-7.

    PMID: 32760450
  2. 2

    Ring chromosome formation by intra-strand repairing of subtelomeric double stand breaks and clinico-cytogenomic correlations for ring chromosome 9.

    Chai H, Ji W, Wen J, et al.

    American journal of medical genetics. Part A 2020; (182(12)):3023-3028 doi:10.1002/ajmg.a.61890.

    PMID: 32978894
  3. 3

    Two Cases with Ring Chromosome 13 at either End of the Phenotypic Spectrum.

    Çakmaklı S, Çankaya T, Gürsoy S, et al.

    Cytogenetic and genome research 2017; (153(4)):175-180 doi:10.1159/000486775.

    PMID: 29518772
  4. 4

    Deletion of Chromosome 13 due to Different Rearrangements and Impact on Phenotype.

    Bellucco FT, Rodrigues de Oliveira-Júnior H, Santos Guilherme R, et al.

    Molecular syndromology 2019; (10(3)):139-146 doi:10.1159/000497402.

    PMID: 31191202
  5. 5

    [Prenatal genetic diagnosis of a case with ring chromosome 13].

    Sun L, Wen J, Chu G, et al.

    Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 2023; (40(12)):1455-1460 doi:10.3760/cma.j.cn511374-20220705-00451.

    PMID: 37994123
  6. 6

    Molecular and Cytogenetic Characterization of a Fetus with Mosaic Ring Chromosome 13: A Very Rare Case.

    Zhao XR, Han X, Wang YL, Hu WJ

    Chinese medical journal 2017; (130(24)):3007-3008 doi:10.4103/0366-6999.220308.

    PMID: 29237938
  7. 7

    Complex biology of constitutional ring chromosomes structure and (in)stability revealed by somatic cell reprogramming.

    Nikitina TV, Kashevarova AA, Gridina MM, et al.

    Scientific reports 2021; (11(1)):4325 doi:10.1038/s41598-021-83399-3.

    PMID: 33619287
  8. 8

    Human ring chromosome registry for cases in the Chinese population: re-emphasizing Cytogenomic and clinical heterogeneity and reviewing diagnostic and treatment strategies.

    Hu Q, Chai H, Shu W, Li P

    Molecular cytogenetics 2018; (11()):19 doi:10.1186/s13039-018-0367-3.

    PMID: 29492108
  9. 9

    Ring chromosome in myeloid neoplasms is associated with complex karyotype and disease progression.

    Rosenbaum MW, Pozdnyakova O, Geyer JT, et al.

    Human pathology 2017; (68()):40-46 doi:10.1016/j.humpath.2017.08.009.

    PMID: 28842184
  10. 10

    Prenatal diagnosis of a fetus with mosaic ring chromosome 13: Case report and review of the literature.

    Hu XN, Li LL, Shi QY, et al.

    Taiwanese journal of obstetrics & gynecology 2021; (60(3)):554-558 doi:10.1016/j.tjog.2021.03.031.

    PMID: 33966748
  11. 11

    A NEW OBSERVATION OF 13q DELETION SYNDROME: SEVERE UNDESCRIBED FEATURES.

    Garcia-Rodriguez E, Garcia-Garcia E, Perez-Sanchez A, Pavon-Delgado A

    Genetic counseling (Geneva, Switzerland) 2015; (26(2)):213-7.

    PMID: 26349191
  12. 12

    Mosaic Ring Chromosome 13 Presented with Isolated Male Infertility: Case Report.

    Zamanian M, Sajadi H, Tahsili M, et al.

    International journal of fertility & sterility 2023; (17(3)):215-217 doi:10.22074/ijfs.2022.548793.1262.

    PMID: 37183849
  13. 13

    13q Deletion Syndrome Involving RB1: Characterization of a New Minimal Critical Region for Psychomotor Delay.

    Privitera F, Calonaci A, Doddato G, et al.

    Genes 2021; (12(9)) doi:10.3390/genes12091318.

    PMID: 34573300

This overview of Ring Chromosome 13 Syndrome is for educational purposes only. Always consult your pediatric geneticist and medical team to interpret your child's specific microarray or karyotype results.

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