Chromosome 5p duplication

The signs and symptoms caused by a chromosome 5p duplication vary widely from person to person. In general, when there has been a gain of chromosomal material, the associated symptoms might include a combination of physical problems, health problems, learning difficulties and/or challenging behavior. These symptoms largely depend on the location of the duplication on the p arm and the genes that are affected. There are general characteristics of chromosome abnormalities that occur in the majority of affected people to varying degrees. Most people with any loss or gain of material will have some degree of learning disability and developmental delay. This is because there are many genes located across all these chromosomes that provide instructions for normal development and function of the brain. Defects in any one of them could affect a person’s development.^[2]

There is limited information on how chromosome abnormalities like duplication 5p15.2pter impact growth and development. Since each abnormality is usually so rare, there are few cases to learn from, let alone conduct research. It is generally difficult to say what the future will hold for affected individuals, because even when the chromosome abnormalities are similar the health problems can vary widely.^[2]

In general, many affected infants and children with a 5p duplication have abnormalities that include low muscle tone (hypotonia); an unusually large head (macrocephaly), and additional abnormalities of the head and facial (craniofacial) area; long, slender fingers (arachnodactyly); developmental delay; and intellectual disability. Some affected individuals may have heart defects and seizures. It is important to understand, however, that not all individuals with a duplication of 5p will have all of the aforementioned symptoms. In fact, some individuals may only experience developmental delay and intellectual disability and may not exhibit any other physical findings.^[3]

The range and severity of associated symptoms and findings depend on the length and location of the duplicated portion of the chromosome. Characteristic physical features of 5p duplications have been reported in individuals with complete duplications of 5p as well as those with various partial duplications. Comparison of the features and the overlapping areas, allows for the definition of a critical region for various features. The critical region for heart abnormalities and seizures is the duplication of 15p13.3. Most physical features are due to a duplication of the bands 5p11 to 5p13.3.^[3]

The critical region for developmental delay and intellectual disability is thought to be the duplication of 5p14 to 5p15. Those who only have the duplication of 5p14 to 5p15 may not have any physical findings. Two boys have been reported with no intellectual disability that have duplication from 5p15.1 to 5p15.3 near the terminus (which is toward the terminus but beyond the area for reported intellectual disability).^[3]

The exact cause is unknown; but in most cases, 5p duplications appears to be caused by random (de novo) errors very early in embryonic development. In such instances, the parents of the affected child usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality. You will need to speak with a genetics professional about how a specific chromosome abnormality might be inherited in your family.^[3]