Chromosome 21q deletion

Alternate names

Deletion 21q; Monosomy 21q; 21q deletion; 21q monosomy; Partial monosomy 21q

Definition

Chromosome 21q deletion is a chromosome abnormality that occurs when there is a missing copy of the genetic material located on the long arm (q) of chromosome 21.

Deletion of chromosome section

File:Human chromosome 21 ideogram.svg

Cause

This condition occurs when there is a missing copy of the genetic material located on the long arm (q) of chromosome 21.

Inheritance

Most cases are not inherited, but people can pass the deletion on to their children.

Signs and symptoms

• The severity of the condition and the signs and symptoms depend on the size and location of the deletion and which genes are involved.
• Features that often occur in people with chromosome 21q deletion include developmental delay, intellectual disability, behavioral problems, and distinctive facial features.

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 is based on the signs and symptoms present in each person.

NIH genetic and rare disease info

• NIH info on Chromosome 21q deletion

Chromosome 21q deletion is a rare disease.