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Prion disease
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Prion disease

Prion diseases are a group of rare, progressive, and fatal conditions that damage the nervous system by causing abnormal protein accumulation in the brain.

Overview

Prion disease represents a group of conditions that affect the nervous system in humans and animals. These conditions impair brain function, causing changes in memory, personality, and behavior; a decline in intellectual function (dementia); and abnormal movements, particularly difficulty with coordinating movements (ataxia). Symptoms typically begin in adulthood and worsen over time, leading to death within a few months to several years.

Causes

Prion diseases are caused by the accumulation of an abnormal protein in the brain. The PRNP gene provides instructions for making a normal prion protein (PrPC). In prion disease, this protein is transformed into an abnormal form (PrPSc). The abnormal protein builds up in the brain, forming clumps that destroy neurons and create microscopic sponge-like holes (vacuoles).

Classification of Cases

  • Familial (10–15%): Caused by mutations in the PRNP gene. These include familial Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), and fatal familial insomnia (FFI).
  • Sporadic (85–90%): Occurs when PrPC spontaneously transforms into PrPSc for unknown reasons. These include sporadic Creutzfeldt-Jakob disease (sCJD), sporadic fatal insomnia (sFI), and variably protease-sensitive prionopathy (VPSPr).
  • Acquired: Results from exposure to PrPSc from an outside source, such as eating contaminated beef products (variant CJD) or ritualistic cannibalism (kuru).
  • Iatrogenic (1–2%): Transmitted by accidental exposure to PrPSc-contaminated tissues during a medical procedure.

Frequency

These disorders are very rare, affecting about one person per million worldwide each year. Approximately 350 new cases are reported annually in the United States.

Inheritance

Familial forms of prion disease are inherited in an autosomal dominant pattern, meaning one copy of the altered PRNP gene is sufficient to cause the disorder. While many affected individuals inherit the gene from a parent, some cases are caused by a de novo mutation that occurs during the formation of reproductive cells or in early embryonic development. Sporadic, acquired, and iatrogenic forms of prion disease are not inherited.

Frequently Asked Questions

Early symptoms of prion disease often start subtly with memory lapses, personality changes, or difficulty with coordination. If you notice progressive confusion, rapid forgetfulness, or new problems with balance and gait that worsen over weeks to months, it is important to see a neurologist promptly. A thorough neurological exam, brain MRI, EEG, and cerebrospinal fluid (CSF) analysis for 14‑3‑3 protein or RT‑QuIC can help differentiate prion disease from other causes of dementia or ataxia.
The only known food‑borne form is variant CJD, linked to consumption of infected bovine products. In most countries, beef is rigorously tested, and the risk is extremely low. Iatrogenic transmission can occur through contaminated surgical instruments or transplanted tissues; modern sterilization protocols and screening of donors greatly reduce this risk. If you are a healthcare worker, follow standard infection‑control guidelines and use dedicated instruments for patients with suspected prion disease.
Sequencing of the PRNP gene can identify pathogenic mutations associated with familial CJD, GSS, or FFI. A positive result confirms a hereditary form and indicates a 50 % chance of passing the mutation to offspring. Genetic counseling is essential to discuss reproductive options, surveillance strategies, and the implications for family members.
Currently there is no proven cure or disease‑modifying therapy for prion disease. Management focuses on supportive care—pain control, physical therapy, speech therapy, and nutritional support—to maintain quality of life. Experimental treatments, such as antisense oligonucleotides or small‑molecule inhibitors, are under investigation in clinical trials, but participation requires careful evaluation by a specialist.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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