The Generative Brain

Inherited prion disease explained

More detail

Inherited prion disease is prion disease caused by a change in PRNP, the gene for prion protein. It accounts for roughly 10 to 15 in every 100 cases. The change can pass from parent to child, and the conditions it causes include familial CJD, fatal familial insomnia and Gerstmann-Straussler-Scheinker syndrome.

How a gene change passes through a family
  • 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.

Everyone carries two copies of PRNP, the gene with the instructions for making prion protein. In a family with inherited prion disease, one of those copies carries a change that makes the protein more likely to misfold.

Which conditions are the inherited ones?

Three names come up most often. Familial Creutzfeldt-Jakob disease, usually shortened to familial CJD. Fatal familial insomnia, in which trouble sleeping is an early and prominent feature. Gerstmann-Straussler-Scheinker syndrome, which often begins with unsteadiness and tends to run a slower course.

Those names were given to patterns that doctors saw before the gene was known. Specialists now often use the single term genetic prion disease, because people in the same family, and even people with the same gene change, can have quite different illnesses.

How does it pass down a family?

One altered copy of the gene is enough for the illness to be possible, so it does not skip generations in the way some other conditions do. Each child of a person who carries the change may inherit it, and relatives are usually told that the chance for each child is one in two. A few people have a new change that neither parent carried.

Carrying the change does not work like a timetable. For some gene changes nearly everyone who carries them becomes ill eventually, while others are carried by many more people than ever develop symptoms. A 2022 review describes these conditions as having variable penetrance, which is the term for that difference. Your family’s own picture is a question for a genetic counsellor, who has the current figures for a particular change.

Does inherited prion disease look different from the other forms?

It usually begins younger than sporadic CJD, and some inherited forms last longer, closer to two years rather than months. The symptoms themselves overlap with the other forms: memory and thinking changes, unsteadiness, changes in mood or personality, and later difficulty with speech, swallowing and movement. Symptoms describes them in order.

Care is the same in kind as for any prion disease, and a palliative care team can be involved early. Care and support covers that.

Can other people in the family catch it?

No. There is no evidence that CJD passes from person to person through ordinary social contact or ordinary nursing at home.

Two practical things do follow a family history. People with prion disease, and relatives at increased risk because of family or medical history, cannot give blood or organs. It also helps to tell a care team about the family history before surgery or dental work.

What do I do with this information?

If a gene change has been found in your family, or you think one may run in it, the next step is a genetic counsellor rather than a test. They can tell you what is actually known about your family, which this page cannot. Genetic counselling comes first explains those appointments, and testing is voluntary. Choosing not to find out is a valid choice.

For the research literature and the detail behind this page, see more detail. Insurance and work covers the practical worries, and family planning options is for people thinking about children. Genetics and family risk is the hub for this section.

Nothing here can tell you what is happening in one family. The treating neurologist and a genetic counsellor are the people who can.

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