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Acute necrotizing encephalopathy type 1
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Acute necrotizing encephalopathy type 1

Acute necrotizing encephalopathy type 1 is a rare brain disease triggered by viral infections that can lead to severe neurological decline and permanent brain damage.

Overview

Acute necrotizing encephalopathy type 1 (also known as IIAE3) is a rare brain disease (encephalopathy) that occurs following a viral infection, such as the flu. It typically appears in infancy or early childhood, though it can manifest in adolescence or adulthood.

Symptoms

Affected individuals usually show typical infection symptoms—such as fever, cough, congestion, vomiting, and diarrhea—for a few days. These are followed by neurological problems, including:

  • Seizures
  • Hallucinations
  • Difficulty coordinating movements (ataxia)
  • Abnormal muscle tone
  • Coma, which may last for several weeks

The condition causes lesions in specific brain regions, leading to swelling (edema), bleeding (hemorrhage), and tissue death (necrosis). While some survivors recover completely, others experience permanent impairments in walking, speech, and basic functions. Approximately half of affected individuals are susceptible to recurrent episodes, with neurological function worsening after each event.

Causes

Variants in the RANBP2 gene increase the risk of developing this condition. The RANBP2 protein helps regulate the transport of molecules through the nuclear pore of cells and plays roles in cell division. While the exact mechanism is unclear, researchers suspect that an abnormal immune response to a viral infection—rather than the virus itself—causes the neurological damage. Common triggers include influenza, human herpesvirus 6, coxsackie virus, and enteroviruses.

Inheritance

This condition is inherited in an autosomal dominant pattern. Having one copy of the altered gene is sufficient to increase the risk of the disorder following an infection. It is characterized by reduced penetrance; not everyone with the mutation will develop the condition, and it is estimated that carriers have a 40 percent chance of developing the disorder during their lifetime.

Frequently Asked Questions

If a child develops seizures, sudden loss of consciousness, severe headache, vomiting that does not improve, or any change in level of alertness within days of a flu‑like illness, seek emergency care immediately. These can signal the rapid onset of brain swelling or bleeding that requires urgent imaging and treatment.
MRI of the brain is the preferred imaging modality and should be obtained as soon as possible, ideally within 24 hours of symptom onset. Blood tests for inflammatory markers, liver enzymes, and lactate levels are also useful and should be drawn concurrently to help differentiate acute necrotizing encephalopathy from other causes of encephalopathy.
High‑dose intravenous steroids and intravenous immunoglobulin (IVIG) are commonly used to dampen the immune response. In some cases, plasma exchange or targeted antiviral therapy may be considered if a specific virus is identified. Early initiation of these therapies, ideally within the first 48–72 hours, is associated with better neurological outcomes.
bout 50% of patients experience recurrent episodes. Regular neurological evaluations every 3–6 months, along with brain MRI at least annually, are recommended. Parents should be educated to recognize early infection symptoms and seek prompt medical care to reduce the risk of a second episode.
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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