Fatal familial insomnia

What it is

From: Orphanet

A rare inherited human prion disease characterized by adult onset of progressive disturbance and loss of circadian rhythms, dysautonomia with increased sympathetic activity, and cognitive impairment with fluctuating vigilance, impaired long-term memory, disorientation, and oneiric states. Motor disturbances include myoclonus, cerebellar ataxia, and pyramidal signs. The disease rapidly leads to a somnolent or comatose state and is typically fatal after 9 or 30 months on average (bimodal course). Neuropathologic examination shows marked neuronal loss and gliosis predominantly in thalamic nuclei and inferior olives, while deposition of abnormal prion protein may be relatively sparse.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal autonomic nervous system physiology · Very frequent (99-80%)

A functional abnormality of the autonomic nervous system.

Dementia · Very frequent (99-80%)

A loss of global cognitive ability of sufficient amount to interfere with normal social or occupational function. Dementia represents a loss of previously present cognitive abilities, generally in adults, and can affect memory, thinking, language, judgment, and behavior.

Insomnia · Very frequent (99-80%)

Persistent difficulty in starting or maintaining sleep, or waking up earlier than desired, despite having adequate opportunities and conditions for sleep.

Myoclonus · Very frequent (99-80%)

Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements.

Abnormality of extrapyramidal motor function · Frequent (79-30%)

A neurological condition related to lesions of the basal ganglia leading to typical abnormalities including akinesia (inability to initiate changes in activity and perform volitional movements rapidly and easily), muscular rigidity (continuous contraction of muscles with constant resistance to passive movement), chorea (widespread arrhythmic movements of a forcible, rapid, jerky, and restless nature), athetosis (inability to sustain the muscles of the fingers, toes, or other group of muscles in a fixed position), and akathisia (inability to remain motionless).

Anxiety · Frequent (79-30%)

Intense feelings of nervousness, tension, or panic often arise in response to interpersonal stresses. There is worry about the negative effects of past unpleasant experiences and future negative possibilities. Individuals may feel fearful, apprehensive, or threatened by uncertainty, and they may also have fears of falling apart or losing control.

Ataxia · Frequent (79-30%)

Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

Bradyphrenia · Frequent (79-30%)

An inner sense from the self that thoughts are abnormally slow and the individual feels that they are unable to increase their rate of thinking. The primary pathology is the decreased rate and other qualities of thinking (e.g. naming of objects) are intact, just slowed. This may be associated with slowed speech, but may be internal and masked by speech that is limited to brief (yes or no) answers.

Cognitive impairment · Frequent (79-30%)

Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering.

Depression · Frequent (79-30%)

Frequently experiencing feelings of being down, miserable, and/or hopeless; struggling to recover from these moods; having a pessimistic outlook on the future; feeling a pervasive sense of shame; having a low self-worth; experiencing thoughts of suicide and engaging in suicidal behavior.

Dysarthria · Frequent (79-30%)

Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.

Dysphagia · Frequent (79-30%)

Difficulty in swallowing.

Emotional lability · Frequent (79-30%)

Unstable emotional experiences and frequent mood changes; emotions that are easily aroused, intense, and/or disproportionate to events and circumstances.

Epiphora · Frequent (79-30%)

Abnormally increased lacrimation, that is, excessive tearing (watering eye).

Other findings in the same source

From: Orphanet

Additional reported features include Hallucinations (Frequent (79-30%)); Hyperhidrosis (Frequent (79-30%)); Hypertension (Frequent (79-30%)); Laryngeal stridor (Frequent (79-30%)); Reduced attention regulation (Frequent (79-30%)); Short term memory impairment (Frequent (79-30%)); Sleep apnea (Frequent (79-30%)); Sleep-wake cycle disturbance (Frequent (79-30%)); Tachycardia (Frequent (79-30%)); Thalamic hypometabolism in FDG PET (Frequent (79-30%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adult

Inheritance in the source

From: Orphanet

Autosomal dominant

Frequency and the population described

From: Orphanet

Reported case(s): 27.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal dominant pattern means that one altered copy of a relevant gene can be sufficient for the condition. Some affected people inherit the change; others have a new change without an affected parent. The precise finding, family history and condition determine what this means for relatives.

Which doctor should you see?

The suggested department for discussing Fatal familial insomnia is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Fatal familial insomnia. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.