What is DICER1 syndrome?
DICER1 syndrome is a rare disorder that makes a person more likely to develop certain types of tumors, both benign (non-cancerous) and malignant (cancerous). Children with this syndrome can develop one or more tumors in these areas of the body:
- Thyroid gland
- Brain (pineal and pituitary glands)
In babies and young children with DICER1 syndrome, the most common type of tumor appears in the lung, and is known as pleuropulmonary blastoma (PPB).
What causes DICER1 syndrome?
DICER1 syndrome is caused by changes in a gene known as DICER1. Genes carry important information that tells our body’s cells how to function. In ways that are not well understood, DICER1aids in preventing tumors.
Most cells of the body carry two working copies of the DICER1 gene. One is inherited from the mother and one from the father. Cells from people with DICER1 syndrome carry one working DICER1 gene copy and one copy that is altered. This alteration causes the gene to not work properly and is called a mutation.
What is the cancer risk for children with DICER1 syndrome?
- PPB, a rare type of lung tumor usually occurring before 6 years of age
- Ovarian sex-cord stromal tumors, such as Sertoli-Leydig cell tumor
- A rare and non-cancerous kidney tumor known as cystic nephroma
- An enlarged thyroid gland that contains growths known as nodules
- A type of eye tumor known as ciliary body medulloepithelioma
- A type of muscle cancer known as rhabdomyosarcoma (specifically, botryoid-type embryonal)
- A type of nose tumor known as nasal chondromesenchymal hamartoma
- Types of brain tumors known as pineoblastoma and pituitary blastoma
The exact risks for developing these tumors are not known at this time. Other tumor types have been described.
How are people with DICER1 syndrome screened for cancer?
In general, tumor screening involves undergoing certain tests to check for tumors before symptoms occur. The goal is to detect tumors at the earliest and most treatable stage. Currently, no common screening guidelines exist for people with this syndrome. The tumor screening tests should be discussed with a doctor who knows this syndrome well.
Screening test may include the following:
- Full physical exams
- Chest imaging
- Renal (kidney) ultrasound
- Thyroid exam
- Eye exam
- Brain MRI
- Pelvic ultrasound (for females)
- Gynecological exam (for females)
How do children get DICER1 syndrome?
Most people with DICER1 syndrome inherit it from a parent who also has the syndrome. But some people with DICER1 syndrome may have a new DICER1 mutation (alteration) that did not come from a parent. In these cases, the DICER1 mutation is new in these people and they are the first in their families to have DICER1 syndrome.
No matter how they acquired the mutation, all people with DICER1 syndrome have a 50% or 1 in 2 chance of passing it on to their children.
How is genetic testing for DICER1 syndrome done?
Hereditary cancer syndromes such as DICER1 syndrome may be suspected after looking at a person’s medical or family history. In most cases, a doctor or genetic counselor will ask questions about a person’s health and the health of other family members.
The genetic counselor or doctor will record which family members have developed tumors, and if so, the types of tumors and ages at which these tumors occurred. From this information, they will create a family tree. Doctors and genetic counselors will examine the family tree to find out:
- If there are more tumors than normal,
- Whether tumors occurred at younger than expected ages, or
- If the types of tumors match up with what might be observed in those with DICER1 syndrome.
Doctors or genetic counselors who suspect DICER1 syndrome in a child or other family members will likely recommend genetic testing of DICER1.
If doctors or genetic counselors suspect a person has DICER1 syndrome, diagnostic testing may take place:
- A blood sample is collected.
- DNA is isolated from the cells in the sample, and the DICER1 gene is checked for possible mutations using a variety of methods such as DNA sequencing. DNA sequencing is when a genetic specialist checks the lettering (spelling) of the two copies of a gene to that of a normal sample. If there are differences, the specialist then decides if they might cause a specific disease, such as DICER1 syndrome. Please note that other methods may also be used, especially when the results of DNA sequencing are negative or unclear. These other tests look for changes that could affect the DICER1 gene but that may not be found by DNA sequencing.
- If a DICER1 mutation is found, a genetic counselor will work with the family to find out if other family members should consider testing for the mutation. The genetic counselor will help the family understand the tumor risks of those with DICER1 syndrome. The genetic counselor can also help with decisions about prenatal genetic testing. can also help with decisions about prenatal genetic testing.
Parents may undergo prenatal testing to find out whether a pregnancy is affected with a knownDICER1 mutation in the family.
Testing may take place either before pregnancy occurs or after an embryo is formed. Those considering prenatal testing should work with a genetic counselor to review the pros and cons of the tests. The genetic counselor will also help parents consider how they wish to handle the results of the testing.
Testing that occurs before pregnancy — Testing that happens before pregnancy is called preimplantation genetic diagnosis (PGD). This special type of genetic testing is done along with in vitrofertilization (IVF). PGD offers a way to test embryos for a known DICER1 mutation before placing them into the uterus.
Testing that occurs during pregnancy — Testing can be used to determine if a pregnancy is affected with a known DICER1 mutation. A doctor gathers cells from the pregnancy in one of two ways:
- Chorionic villus sampling (CVS) — during first trimester
- Amniocentesis — during second trimester or later
Once these tissues are collected, DNA is isolated and checked for the presence of the DICER1mutation identified in the family.
Both of these tests carry minor risks and should be discussed with an experienced doctor and/or genetic counselor.
Genetic testing for DICER1 syndrome is a complex process. Those thinking about testing should take time to consider the benefits and risks. They should discuss the process with a genetic counselor before undergoing the testing. If they choose testing, they should review the test results with the doctor or genetic counselor to be sure that they understand the meaning of the results.
Sometimes, children or adults with DICER1 syndrome experience sadness, anxiety or anger. Parents who passed on an altered DICER1 gene to one or more of their children can feel guilty. It is also possible that a person who is found to have an altered DICER1 gene could have more trouble getting disability insurance or life insurance. Read more about genetic discrimination.
The St. Jude Web site is designed for educational purposes only and is not engaged in rendering medical advice or professional services. The information provided through this site should not be used for diagnosing or treating a health problem or a disease. It is not a substitute for professional care. If you have or suspect you may have a health problem, you should consult your health care provider.