- Carries a changed copy of PRNP
- Does not carry it
- 50%chance for each child
Each child of a parent with the change has a 50 percent chance of inheriting it. The drawing shows two of four children for simplicity; each chance is separate, so a real family can differ. Whether someone who inherits it becomes ill depends on the change. A genetic counsellor can explain what applies in a family. Each adult decides for themselves whether to find out.
Learning that a prion disease in the family is inherited raises questions that reach into the future. There is no deadline on any of them. Nothing on this page needs to be decided today.
What does inherited mean here?
A small share of prion disease, around one in ten cases, is caused by a change in the gene that makes the prion protein. The change is passed from parent to child. Because it is dominant, a parent who carries it has a one in two chance of passing it on with each child. These forms include genetic CJD, Gerstmann-Straussler-Scheinker disease and fatal familial insomnia, and they often begin younger and progress more slowly than sporadic CJD.
Relatives of someone with sporadic CJD, the most common form, are in a different position: there is no evidence that they have an increased likelihood of the illness. If you do not yet know which form your relative had, ask about that first. Inherited prion disease explained goes further.
The next three steps
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Gather the facts about your own family. The UK support network’s advice is to have all the necessary factual information before any decision, and to talk with everyone who may be affected. That can mean finding out whether a gene change was identified in a relative, and which one.
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Ask for a referral to a genetic counsellor with experience of prion disease. Counselling comes first, before any test, and it is a conversation about options, timing and what a result would and would not mean for you and the people around you. In the UK, ask the GP or the National Prion Clinic. In the United States, the CJD Foundation helpline on 1-800-659-1991 can suggest how to find a genetic counselling professional. Counselling first explains what to expect.
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Talk to people who have been here. The CJD Support Network supports people at increased risk as well as those who are ill, on 0800 774 7317. The CJD Foundation runs peer sessions for people at risk of genetic prion disease. Someone I love has been diagnosed covers the care side if a relative is ill now.
Do I have to be tested?
No. Testing is available, and a decision to test, to wait or never to test are all reasonable choices. Some people want to know; some prefer not to, and The right not to know is about them. For people thinking about children, the UK support network notes that there are techniques which may allow a child to be born without the family’s gene change, and a genetic counsellor can explain them.
If your concern is about something other than inheritance, I am worried about exposure is the page for that. The Start here page lists every route.
What any of this means for one person is a question for a genetic counsellor or doctor who knows the family history. No page can answer it.