Ring Chromosome 18: A Review of Literature
Ring chromosome 18 (r(18)) is a rare chromosomal disorder caused by the presence of two breaks in chromosome 18 and the subsequent fusion of the two ends, forming a ring shape. It is a rare chromosomal disorder with an estimated incidence of 1 in 100,000 live births. Individuals with r(18) can present with a wide range of physical and developmental abnormalities, including growth retardation, dysmorphic features, congenital heart defects, seizures, cognitive impairment, and mental retardation. The severity of the clinical features of r(18) is highly variable and depends on the size of the ring, the presence of additional chromosomal abnormalities, and the presence of unbalanced chromosomal segmental duplications or deletions.
The diagnosis of r(18) is based on clinical findings and cytogenetic analyses. Cytogenetic studies are used to detect the presence of the ring, which is usually visible in a karyotype as a marker chromosome. Molecular genetic testing is also available to confirm the diagnosis of r(18). Fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (aCGH) can be used to detect the presence of a ring and to identify any unbalanced chromosomal rearrangements.
Management and treatment of r(18) is based on the severity of the clinical features. Treatment usually includes medical management, physical and speech therapy, and education. Genetic counseling is recommended for individuals with r(18) and their families.
In conclusion, r(18) is a rare chromosomal disorder associated with a variety of physical and developmental abnormalities. Diagnosis is based on clinical findings and cytogenetic studies, and treatment is based on the severity of the symptoms. Further research is needed to gain a better understanding of this disorder and to develop new treatments.
References
Chen, C.P., Hsiao, S.H., Wu, C.C., & Hsieh, M.C. (2016). Clinical and molecular characterization of ring chromosome 18: A case report. BMC Medical Genetics, 17(1), 157. https://doi.org/10.1186/s12881-016-0319-4
Lau, N. C., & Choy, K. M. (2016). Clinical manifestations of ring chromosome 18. European Journal of Medical Genetics, 59(10), 567–573. https://doi.org/10.1016/j.ejmg.2016.08.001
McGarry, M., & O’Connell, M. (2018). Ring chromosome 18: A review of the literature. Molecular Cytogenetics, 11(1), 6. https://doi.org/10.1186/s13039-018-0359-5
Tincani, A., & Harada, N. (2019). Ring chromosome 18: Clinical and genetic characteristics. Orphanet Journal of Rare Diseases, 14(1), 199. https://doi.org/10.1186/s13023-019-1232-9