Chromosome 3p- syndrome

In most people with chromosome 3p- syndrome, the deletion occurs as a new mutation (called a de novo mutation) and is not inherited from a parent. De novo mutations are due to a random error that occurs during the formation of egg or sperm cells, or shortly after conception. In a few cases, the deletion is inherited from a parent.

There are several different specialized tests that can be used to diagnose a chromosome 3p- syndrome. These include:

• 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 duplication of a specific region of 3p.
• Array CGH - a technology that detects deletions that are too small to be seen on karyotype.

In most cases, chromosome 3p- syndrome occurs for the first time in the affected person ( de novo mutation). However, the deletion is rarely inherited from a parent. In these cases, the deletion is passed down in an autosomal dominant manner. This means that a person with chromosome 3p- syndrome has a 50% chance with each pregnancy of passing the condition on to his or her child.

In theory, it is possible for a parent to not have the deletion in their chromosomes on a blood test, but have the deletion in some of their egg or sperm cells only. This phenomenon is called germline mosaicism. In these rare cases, it would be possible to have another child with the deletion. To our knowledge, this has not been reported with chromosome 3p- syndrome.

People interested in learning more about genetic risks to themselves or family members should speak with a genetics professional.

The long-term outlook (prognosis) for people with chromosome 3p- syndrome varies from person to person. The severity of the condition and the associated signs and symptoms largely depend on the size and location of the deletion and the genes involved.

Because chromosome 3p- syndrome affects many different systems of the body, medical management is often provided by a team of doctors and other healthcare professionals. Treatment for this deletion varies based on the signs and symptoms present in each person. For example, children with delayed motor milestones (i.e. walking) and/or muscle problems may be referred for physical or occupational therapy. Severe feeding difficulties may be treated temporarily with a nasogastric tube or a gastrostomy tube to ensure that a baby or child gets enough nutrients. Certain medications may be prescribed to treat seizures. Special education services are often necessary for children with intellectual disability. Surgery may be required to treat certain physical abnormalities such as cleft palate or congenital heart defects, if present.

Please speak to your healthcare provider if you have any questions about your personal medical management plan.