What is a syndrome?


A syndrome is a medical term that describes a group of signs, symptoms, or characteristics commonly occurring together and linked to a specific condition or disease. Some syndromes are genetic (inherited from parents), while others result from environmental factors, infections, or a combination of different influences.

Familial cancer syndromes are inherited syndromes that significantly increase a person’s risk of developing certain types of cancer.

What causes a familial cancer syndrome?

Genetic mutations or changes usually cause familial cancer syndromes. These syndromes affect important genes controlling how cells grow, divide, or repair themselves. When these genes aren’t working correctly, cells can grow uncontrollably, increasing the likelihood of developing cancer.

These genetic mutations can be passed down through families from parents to children.

What is the risk of inheriting a familial cancer syndrome?

The risk of inheriting a familial cancer syndrome depends on how the syndrome is passed from parents to children. Most familial cancer syndromes follow one of two inheritance patterns:

Autosomal dominant inheritance

In autosomal dominant syndromes, you only need to inherit one copy of the altered gene from either parent to be at risk for developing the syndrome.

  • Risk of inheritance: If one parent has the gene mutation, each child has a 50% chance of inheriting and developing the syndrome. This risk is the same with each pregnancy, regardless of the results of other siblings.

  • Examples: Lynch syndrome, hereditary breast and ovarian cancer syndrome (BRCA1/BRCA2), and Li-Fraumeni syndrome.

Autosomal recessive inheritance

In autosomal recessive syndromes, you must inherit two copies of the altered gene (one from each parent) to develop the syndrome. People who inherit only one altered gene are called carriers; they usually do not develop the syndrome themselves.

  • Risk of inheritance if both parents are carriers:

    • 25% chance a child will inherit two altered genes and develop the syndrome.

    • 50% chance a child will inherit one altered gene and be a carrier.

    • 25% chance a child will inherit no altered genes and neither develop the syndrome nor be a carrier.

If only one parent is a carrier, children won’t develop the syndrome, but there’s a 50% chance they’ll become carriers.

  • Examples: MUTYH-associated polyposis (MAP).

What are some common familial cancer syndromes?

Here are some of the most common familial cancer syndromes:

Lynch syndrome (Hereditary nonpolyposis colorectal cancer)

  • Genes involved: MLH1, MSH2, MSH6, PMS2, EPCAM

  • Inheritance: Autosomal dominant

  • Cancers: Colorectal, endometrial, ovarian, stomach, urinary tract

  • Cancer risk: Up to 70% for colorectal, up to 50% for endometrial cancer

Hereditary breast and ovarian cancer syndrome (BRCA1/BRCA2)

  • Genes involved: BRCA1, BRCA2

  • Inheritance: Autosomal dominant

  • Cancers: Breast, ovarian, prostate, pancreatic

  • Cancer risk: Breast cancer 50–85%; ovarian cancer 20–40%

Familial adenomatous polyposis (FAP)

  • Gene involved: APC

  • Inheritance: Autosomal dominant

  • Cancers: Colorectal, duodenal, thyroid

  • Cancer risk: Nearly 100% risk of colorectal cancer without preventive measures

Li-Fraumeni syndrome

  • Gene involved: TP53

  • Inheritance: Autosomal dominant

  • Cancers: Breast, brain, soft tissue sarcomas, bone cancers

  • Cancer risk: Over 90% lifetime risk of cancer

Peutz-Jeghers syndrome

  • Gene involved: STK11 (LKB1)

  • Inheritance: Autosomal dominant

  • Cancers: Stomach, colon, pancreas, breast, ovarian, testicular

  • Cancer risk: 37%–93%, depending on cancer type

Cowden syndrome

  • Gene involved: PTEN

  • Inheritance: Autosomal dominant

  • Cancers: Breast, thyroid, endometrial, kidney

  • Cancer risk: Breast cancer up to 85%, thyroid cancer up to 35%

Von Hippel-Lindau syndrome

  • Gene involved: VHL

  • Inheritance: Autosomal dominant

  • Cancers: Kidney cancer, adrenal gland tumors, brain tumors

  • Cancer risk: Up to 70% for kidney cancer

Retinoblastoma syndrome

  • Gene involved: RB1

  • Inheritance: Autosomal dominant

  • Cancers: Retinoblastoma (eye cancer), bone cancers, soft tissue sarcomas

  • Cancer risk: About 90% risk of retinoblastoma in early childhood

Multiple endocrine neoplasia type 1 (MEN1)

  • Gene involved: MEN1

  • Inheritance: Autosomal dominant

  • Cancers: Parathyroid, pancreatic, pituitary tumors

  • Cancer risk: High lifetime risk for endocrine tumors

Multiple endocrine neoplasia type 2 (MEN2)

  • Gene involved: RET

  • Inheritance: Autosomal dominant

  • Cancers: Medullary thyroid cancer, adrenal gland tumors, parathyroid tumors

  • Cancer risk: Nearly 100% risk of medullary thyroid cancer if untreated

How do doctors test for familial cancer syndromes?

Doctors use genetic testing to diagnose familial cancer syndromes. Genetic testing involves examining your DNA to find specific mutations associated with these syndromes. Genetic testing may be recommended if you have a family history of cancer or if cancer appears at an unusually young age.

The process typically includes:

  1. Detailed family history: Gather information about the types of cancers in your family and the ages at which they were diagnosed.

  2. Genetic counseling: Meeting with a genetic counselor who explains the testing process, potential outcomes, and implications of results.

  3. DNA testing: A simple blood or saliva sample is tested for genetic mutations.

  4. Interpreting results:

    • A positive result indicates the presence of a known mutation linked to increased cancer risk.

    • A negative result means no known mutations were found, but it does not eliminate inherited risk.

How can knowing your risk help?

Understanding your genetic risk can help you and your doctor develop tailored cancer screening and prevention strategies. It may lead to earlier detection, more effective treatments, and improved health outcomes for you and your family.

Questions to ask your doctor or genetic counselor

If you’re considering genetic testing or have a known familial cancer syndrome, you might ask:

  • Should I get genetic testing based on my family history?

  • What will the test results mean for my health and my family’s health?

  • How might a positive result change my medical care?

  • What preventive measures can I take if I’m at increased risk?

Learning about familial cancer syndromes helps you make informed decisions to protect your health and your family’s well-being.

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