Spinocerebellar ataxia type 3

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Spinocerebellar ataxia type 3 (SCA3) is a condition characterized by progressive problems with movement. People with this condition initially experience problems with coordination and balance (ataxia). Other early signs and symptoms of SCA3 include speech difficulties, uncontrolled muscle tensing (dystonia), muscle stiffness (spasticity), rigidity, tremors, bulging eyes, and double vision. People with this condition may experience sleep disorders such as restless leg syndrome or REM sleep behavior disorder. Restless leg syndrome is a condition characterized by numbness or tingling in the legs accompanied by an urge to move the legs to stop the sensations. REM sleep behavior disorder is a condition in which the muscles are active during the dream (REM) stage of sleep, so an affected person often acts out his or her dreams. These sleep disorders tend to leave affected individuals feeling tired during the day.

Over time, individuals with SCA3 may develop loss of sensation and weakness in the limbs (peripheral neuropathy), muscle cramps, muscle twitches (fasciculations), and swallowing difficulties. Individuals with SCA3 may have problems with memory, planning, and problem solving.

Signs and symptoms of the disorder typically begin in mid-adulthood but can appear anytime from childhood to late adulthood. People with SCA3 eventually require wheelchair assistance. They usually survive 10 to 20 years after symptoms first appear.

ORPHANET DEFINITION Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common subtype of type 1 autosomal dominant cerebellar ataxia (ADCA type 1), a neurodegenerative disorder, and is characterized by ataxia, external progressive ophthalmoplegia, and other neurological manifestations.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Point prevalence: 1-9 / 100 000; Worldwide; Value and class. Point prevalence: 1-9 / 100 000; Portugal; Value and class. Point prevalence: 1-9 / 100 000; Japan; Value and class.

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 pyramidal sign · Very frequent (99-80%)

Functional neurological abnormalities related to dysfunction of the pyramidal tract.

Abnormality of extrapyramidal motor function · Very frequent (99-80%)

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).

Clumsiness · Very frequent (99-80%)

Lack of physical coordination resulting in an abnormal tendency to drop items or bump into objects.

Delayed speech and language development · Very frequent (99-80%)

A degree of language development that is significantly below the norm for a child of a specified age.

Diplopia · Very frequent (99-80%)

Diplopia is a condition in which a single object is perceived as two images, it is also known as double vision.

Dysarthria · Very frequent (99-80%)

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.

Dystonia · Very frequent (99-80%)

An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.

Hyperreflexia · Very frequent (99-80%)

Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.

Nystagmus · Very frequent (99-80%)

Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.

Progressive external ophthalmoplegia · Very frequent (99-80%)

Initial bilateral ptosis followed by limitation of eye movements in all directions and slowing of saccades.

Proptosis · Very frequent (99-80%)

An eye that is protruding anterior to the plane of the face to a greater extent than is typical.

Skeletal muscle atrophy · Very frequent (99-80%)

The presence of skeletal muscular atrophy (which is also known as amyotrophy).

Progressive cerebellar ataxia · Very frequent (99-80%)

Abnormal vestibular function · Occasional (29-5%)

An abnormality of the functioning of the vestibular apparatus.

Other findings in the same source

From: Orphanet

Additional reported features include Abnormality of temperature regulation (Occasional (29-5%)); Vocal cord paralysis (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Adult; Childhood

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal dominant

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Point prevalence: 1-9 / 100 000; Worldwide; Value and class. Point prevalence: 1-9 / 100 000; Portugal; Value and class. Point prevalence: 1-9 / 100 000; Japan; Value and class.

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 Spinocerebellar ataxia type 3 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 Spinocerebellar ataxia type 3. 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.