Chromosome 20p deletion

Alternate names

Deletion 20p; Monosomy 20p; 20p deletion; 20p monosomy; Partial monosomy 20p

Definition

Chromosome 20p deletion is a chromosome abnormality that occurs when there is a missing (deleted) copy of genetic material on the short arm (p) of chromosome 20.

Deletion of chromosome section

1 deletion, 2 duplication and 3 inversion.

Cause

This condition occurs when there is a missing (deleted) copy of genetic material on the short arm (p) of chromosome 20.

Inheritance

• Some 20p deletions are not inherited and occur randomly during the formation of egg or sperm cells, or very early in fetal development.
• Other 20p deletions are present because a parent has a rearrangement of genetic material on his/her chromosomes.
• This rearrangement is usually a balanced translocation, which typically does not cause any health problems.
• Occasionally, a parent has the same deletion as his/her child.
• Chromosome testing of both parents can provide information about whether the deletion was inherited.
• If a parent has the same deletion as the child and does not have signs or symptoms, a genetics doctor usually assumes that the 20p deletion is not the cause of the child’s signs and symptoms.

Signs and symptoms

• The severity and the signs and symptoms depend on the size and location of the deletion and which genes are involved.
• Extremely small deletions (microdeletions) involving the distal end of chromosome 20p are relatively common and in some cases are passed from parent to child without causing any health problems (called a familial variant).
• In other cases, a 20p deletion causes signs and symptoms such as developmental delay, growth delay, learning difficulties, distinctive facial features, birth defects, and/or various medical 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 deletion is based on the signs and symptoms in each person.

NIH genetic and rare disease info

• NIH info on Chromosome 20p deletion

Chromosome 20p deletion is a rare disease.

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