Chromosome 20p duplication

Alternate names

Duplication 20p; Trisomy 20p; 20p duplication; 20p trisomy; Partial trisomy 20p

Definition

Chromosome 20p duplication is a rare chromosome abnormality that occurs when there is an extra copy (duplication) of genetic material on the short arm (p) of chromosome 20.

Epidemiology

Very few cases of chromosome 20p duplication have been reported.

Cause

The majority of those have been partial duplications (involving only part of the p arm) and have occurred as part of a translocation (along with a deletion on another chromosome).

Inheritance

• Most cases of chromosome 20p duplication have resulted from a healthy parent having a chromosomal balanced translocation or inversion (when a piece of a chromosome is facing the wrong direction).
• When a parent has one of these, there is an increased risk to have another child with a chromosome abnormality.
• Some chromosome 20p duplications have resulted from a random genetic error (not inherited), in which both parents have normal chromosomes.
• In these cases, it is unlikely the parents would have another child with a chromosome abnormality.

Signs and symptoms

• The severity of the condition and the signs and symptoms depend on the size and location of the duplication and which genes are involved.
• In general, smaller duplications are less severe than larger duplications.
• Signs and symptoms that have been reported in people with chromosome 20p duplication include intellectual disability, developmental delay, speech delay, poor coordination, dental problems, spinal bone abnormalities, distinctive facial features, and heart problems.

Diagnosis

Chromosome disorders may be suspected in people who have developmental delays, intellectual disabilities and/or physical abnormalities.

Several types of genetic tests can identify chromosome disorders:

• Karyotype - a karyotype is a laboratory test that produces an image of a person's chromosomes. This test can be used to diagnose large deletions.
• FISH - a laboratory technique that is used to detect and locate a specific DNA sequence on a chromosome. During FISH, a chromosome is exposed to a small DNA sequence called a probe that has a fluorescent molecule attached to it. The probe sequence binds to its corresponding sequence on the chromosome. This test can be used in combination with karyotyping for deletions that are too small to be seen on karyotype, alone. However, FISH is only useful if the person ordering the test suspects there is a deletion of a specific region of 4q.
• Array CGH - a technology that detects deletions that are too small to be seen on karyotype.

Treatment

Treatment for chromosome 20p duplications depends on the signs and symptoms present in each person.

NIH genetic and rare disease info

• NIH info on Chromosome 20p duplication

Chromosome 20p duplication is a rare disease.

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