Partial duplication of the long arm of chromosome 18 syndrome

Partial duplication of the long arm of chromosome 18 syndrome (also known as trisomy 18q or partial trisomy 18q) is a rare chromosomal disorder in which a portion of the long arm (q arm) of chromosome 18 is duplicated, resulting in three copies of the genetic material in that region instead of the usual two. The clinical presentation varies depending on the size and specific location of the duplicated segment, but commonly includes intellectual disability, developmental delay, growth retardation, and a range of characteristic facial features such as a flat midface, short palpebral fissures, micrognathia, and ear anomalies. Affected individuals may also present with hypotonia, limb anomalies including short hands and feet, and congenital heart defects. Additional features can include microcephaly, seizures, feeding difficulties in infancy, and skeletal abnormalities. Some patients may have urogenital malformations and visual or hearing impairments. The severity of the condition is highly variable and correlates with the extent of the duplicated chromosomal segment. Larger duplications tend to produce more severe phenotypes with greater involvement of multiple organ systems. There is currently no cure for this condition. Management is supportive and symptomatic, involving a multidisciplinary team that may include pediatricians, cardiologists, neurologists, orthopedic specialists, and developmental therapists. Early intervention programs focusing on speech therapy, physical therapy, and occupational therapy can help optimize developmental outcomes. Surgical correction may be required for congenital heart defects or other structural anomalies. Genetic counseling is recommended for affected families to assess recurrence risk, particularly when the duplication arises from a balanced chromosomal rearrangement in a parent.

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