Huntington's disease
Enable an agent to recognise Huntington's disease, distinguish inherited susceptibility from clinical manifestation, assess progression, and identify evidence-supported assessment and care actions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise Huntington's disease, distinguish inherited susceptibility from clinical manifestation, assess progression, and identify evidence-supported assessment and care actions.
Huntington's disease is an autosomal dominant, progressive neurodegenerative disorder caused by a pathogenic CAG-repeat expansion in the HTT gene, with variable combinations of motor, cognitive and psychiatric manifestations.
It can be Organise genetic and clinical evidence into a reviewable disease-status assessment.; Flag discordant findings and missing evidence for specialist review.; Compare serial assessments when instruments and examination conditions permit.; Identify disease-specific support priorities from swallowing, mobility, cognition, behaviour and functional findings.; Route predictive-testing and family-risk questions to a documented genetic-counselling process.; Attach verified terminology mappings and population estimates without losing their revision or context..
Distinguishing features
Identify evidence of a disease-associated HTT CAG expansion; chorea alone does not establish Huntington's disease. Reference: [GeneReviews](https://www.ncbi.nlm.nih.gov/books/NBK1305/).
Separate a positive predictive genetic result from evidence establishing current clinical manifestation.
Assess progressive motor, cognitive and psychiatric changes together rather than equating the disease with involuntary movement. Reference: [NINDS](https://www.ninds.nih.gov/sites/default/files/2025-05/huntingtons-disease-hope-through-research.pdf).
Allow juvenile presentations with prominent rigidity or bradykinesia rather than requiring adult-pattern chorea. Reference: [GeneReviews](https://www.ncbi.nlm.nih.gov/books/NBK1305/).
Require a documented differential assessment when the phenotype resembles Huntington's disease but HTT evidence is absent, inconclusive or discordant.
Scope
+ HTT repeat-expansion evidence and its interpretation
+ Distinction between familial risk, molecular status and clinically manifest disease
+ Motor, cognitive, psychiatric and functional manifestations
+ Adult and juvenile presentations and longitudinal progression
+ Disease-specific assessment, care priorities and evidence provenance
+ Versioned terminology mappings and population-specific epidemiology
- The patient's complete identity, biography and medical record
- The HTT gene and huntingtin protein as independently modelled biological entities
- Laboratory operations and sequencing-platform specifications
- Visits, referrals and episodes of care as operational records
- Drug products, prescribing protocols and clinical trials as independent entities
- Relatives' individual diagnoses and reproductive decisions
Characteristics
- HTT repeat measurement
- CAG repeat count for each reported allele, with assay, uncertainty and report date Preserves the measured evidence separately from its clinical interpretation.
- Allele interpretation
- Normal, intermediate, reduced penetrance, full penetrance or unresolved, with interpretation authority and revision Conventional ranges are ≤26, 27-35, 36-39 and ≥40 repeats respectively; repeat structure and assay limitations require attention near boundaries. Reference: [GeneReviews](https://www.ncbi.nlm.nih.gov/books/NBK1305/).
- Disease ascertainment status
- Familial risk only, molecularly established expansion without established clinical manifestation, clinically manifest, suspected or unresolved Prevents risk, genetic status and clinical diagnosis from being collapsed.
- Onset evidence
- Age in years or interval, separately for motor, cognitive and psychiatric onset, with informant and certainty Separates recalled first symptoms from formal diagnosis and supports assessment of juvenile presentation.
- Motor assessment
- UHDRS motor scores or another named instrument, with version, date, examiner and examination conditions Makes serial motor observations interpretable without treating every change as progression.
- Cognitive and psychiatric profile
- Domain-specific findings, severity, instrument, informant, date and attribution certainty Captures clinically consequential changes that a motor-only model misses.
- Functional capacity
- Named functional instrument and score, plus assistance required for specific activities Connects observed impairment to support needs.
- Stage assignment
- Framework name, version, assigned stage, supporting evidence and assignment date Prevents clinical functional stages and research classifications from being treated as interchangeable.
- Terminology mapping
- Verified ICD-10, ICD-11 or SNOMED CT identifier, edition, jurisdiction, label and mapping scope Keeps disease codes separate from genetic susceptibility, symptoms and encounter codes.
- Population burden estimate
- Prevalence or incidence with denominator, geography, population definition, observation period and ascertainment method Prevents a local or historically measured estimate from becoming a universal disease property.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 29 questions.
Genetic identity Establish what HTT evidence supports and where its interpretation remains uncertain.
Huntington's disease requires a model of expansion evidence that does not mistake inherited risk for observed clinical state.
Repeat evidence
Retain the original measurement and laboratory interpretation.
Reported HTT expansion
Record allele measurements, assay limitations and repeat-structure information where available.
- What repeat counts were reported for each allele, by which laboratory and assay, and with what measurement uncertainty? measurement
- Which interpretation standard was applied, and could repeat interruptions or assay limitations affect this result? provenance
Inheritance and penetrance
Separate family evidence, transmission and individual expression.
Family evidence limits
Keep pedigree reports distinct from verified genetic findings and avoid deterministic onset predictions.
- Which reported affected relatives have verified diagnoses or molecular results, and which remain family recollections? provenance
- What can this allele interpretation establish about susceptibility, and what remains unknown about whether and when symptoms will occur? boundary
Diagnosis and boundaries Distinguish disease status from a test result, symptom label or encounter.
A molecular finding, a clinical diagnosis and a care episode answer different questions.
Clinical ascertainment
Document the basis and authority for a diagnostic assertion.
Manifestation assertion
Require explicit criteria and supporting observations for the assigned clinical status.
- Which diagnostic criteria, issuing body and revision support the recorded status, and who applied them? provenance
- Does the assertion concern familial risk, an identified expansion, prodromal features or clinically manifest disease? definition
Phenocopies and coding
Resolve competing explanations and terminology boundaries.
Differential and code fit
Record unresolved Huntington-like presentations and verify that coding matches the assertion actually supported.
- If HTT evidence is negative or inconclusive, what assessment is documented for alternatives such as JPH3-related disease, other repeat disorders or acquired chorea? boundary
- Which verified code, release and jurisdiction describe the supported disease assertion rather than a symptom, susceptibility state or visit? provenance
Phenotype and progression Describe domain-specific manifestations and their trajectory.
The clinically relevant state cannot be represented by chorea severity or a single onset date.
Multidomain presentation
Characterise motor, cognitive and psychiatric changes, including juvenile presentations.
Presentation profile
Record observed features, their timing and competing explanations.
- Which choreic, rigid, bradykinetic, dystonic or oculomotor findings are documented, and by what examination? measurement
- Which cognitive or psychiatric changes preceded or followed motor findings, and how were medication effects or comorbid conditions considered? boundary
Longitudinal staging
Connect repeated assessments to a named staging framework.
Supported stage and change
Separate measured change, inferred progression and framework-specific stage.
- Which dated motor, cognitive and functional assessments support the trajectory, and are their instruments and conditions comparable? measurement
- Which staging framework and revision were used, and does the assignment serve clinical care or research classification? boundary
Care priorities and testing Translate disease findings into reviewable support and testing decisions.
Functional consequences and predictive genetic information create distinct action requirements.
Complications and support
Identify current disease-related needs and responsible clinical follow-up.
Priority needs
Record actionable concerns involving swallowing, nutrition, falls, communication, mental health and daily functioning.
- Which current findings indicate a need for swallowing, nutrition, mobility, communication or mental-health assessment? action
- What symptom or functional goal is each intervention intended to address, and what response or adverse effect will be reviewed? action
Predictive testing context
Preserve the purpose, consent context and disclosure boundaries of testing.
Testing purpose and authority
Distinguish diagnostic testing from predictive and reproductive uses of genetic information.
- Is testing diagnostic, predictive or reproductive, and which counselling and consent process applies? boundary
- What consent and professional guidance govern testing or disclosure, particularly for asymptomatic minors and relatives? action
Population and evidence context Keep epidemiological and practice claims attached to their applicable evidence.
Population estimates and clinical recommendations lose meaning when detached from ascertainment, date and scope.
Population ascertainment
Define who was counted and how disease status was established.
Interpretable burden
Separate clinically ascertained disease prevalence from expansion frequency and familial risk.
- What population, geography, year, denominator and diagnostic method support the estimate? measurement
- Does the estimate count clinically manifest cases, expansion carriers or people with family history, and how might underdiagnosis affect it? boundary
Claim maintenance
Track source support and revision-sensitive conclusions.
Evidence and unsettled claims
Attach evidence to diagnostic, prognostic and intervention claims while retaining unresolved disagreement.
- Which directly reviewed source supports each claim, and what publication date, population and limitations constrain it? provenance
- Which claims require renewed verification before use, especially diagnostic revisions, biomarkers and treatment availability? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This is recalled knowledge, not source-verified research; guideline editions and instrument details should be checked before publication.
- Adult, juvenile and late-onset categories describe age at onset rather than separate genetic diseases; late-onset thresholds vary.
- No prevalence estimate or ICD-11/SNOMED CT identifier is supplied because these require verification of population, edition or terminology release.
- Which of these check these first hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Adult-onset Huntington's disease
- Juvenile-onset Huntington's disease
- Late-onset Huntington's disease
- Which of these kinds and varieties hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- WHO ICD-10 - G10 - Huntington's disease; record the coding revision and any national modification.
- OMIM - 143100 - Huntington disease phenotype entry.
- HGNC gene symbol - HTT - Identifies the associated gene, not the disease or an individual expanded allele.
- Which of these identifiers and schemes hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- European Molecular Genetics Quality Network and Clinical Molecular Genetics Society: best-practice guidelines for molecular genetic testing of Huntington disease.
- Huntington Study Group: Unified Huntington's Disease Rating Scale (UHDRS), a standardized clinical assessment instrument.
- World Health Organization: ICD classification for disease coding; the revision must accompany the code.
- Which of these standards and regulation hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Diagnostic evaluation combining clinical assessment, family history and molecular testing.
- Predictive testing of at-risk individuals within genetic counselling pathways.
- Longitudinal assessment of motor function, cognition, psychiatric symptoms and functional capacity.
- Clinical-trial classification and outcome measurement.
- Care planning for mobility, communication, swallowing, nutrition and increasing support needs.
- Which of these real-world use hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- HTT CAG-repeat length - 27-35 is the intermediate range, generally not disease-causing in the carrier but potentially unstable in transmission; 36-39 has reduced penetrance; 40 or more is conventionally classified as fully penetrant over a normal lifespan. - CAG repeats
- Age at clinical onset - Commonly 30-50, with substantial variation; juvenile onset is before 20. - years
- UHDRS Total Motor Score - Instrument range 0-124; higher scores indicate greater motor impairment. - points
- UHDRS Total Functional Capacity - Instrument range 0-13; lower scores indicate greater functional impairment. - points
- Which of these typical measurements hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Progressive swallowing impairment can cause aspiration and malnutrition; motor impairment increases falls risk.
- Depression, behavioural changes and suicide risk require attention throughout the disease course.
- Equating an expanded allele with currently manifest disease confuses genetic status with clinical diagnosis.
- Repeat length cannot precisely predict an individual's onset age, symptom pattern or rate of progression.
- Predictive genetic results have implications for relatives, reproductive decisions, privacy and potential discrimination.
- Which of these failure modes and hazards hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Reported prevalence differs substantially by ancestry and geography; comparisons require a specified population, year and ascertainment method.
- Access to molecular testing, genetic counselling and multidisciplinary care varies between health systems.
- Predictive-testing practices and protections concerning genetic information differ by jurisdiction.
- Which of these regional variation hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Huntington disease-like 2 - A clinically overlapping inherited disorder associated with a JPH3 repeat expansion rather than the pathogenic HTT expansion.
- Wilson disease - An ATP7B-related copper-metabolism disorder distinguished through copper studies, clinical findings and molecular testing.
- Chorea - A movement phenotype with many causes, rather than a specific inherited neurodegenerative disease; chorea alone does not establish Huntington's disease.
- Premanifest HTT expansion-carrier status - Describes an individual carrying a disease-associated expansion before manifest clinical disease; classification depends on the clinical or research framework used.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of Huntington's disease this model covers, and on what evidence? provenance
What the second pass must settle
- Which diagnostic and staging authorities should govern this publication, and how should differences between clinical manifestation criteria and research classifications be represented?
- What are the verified ICD-10, ICD-11 and SNOMED CT mappings in the intended jurisdictions and releases, including separate handling of predictive genetic findings?
- Which laboratory guidance best resolves borderline repeat measurements, repeat interruptions and discordant genotype-phenotype findings?
- Which contemporary population studies provide defensible prevalence and incidence estimates, with explicit ascertainment and representation of juvenile disease?
- Which current guidelines support symptom management, predictive testing in minors and emerging interventions, and what remains investigational?