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Huntington's Disease

DIAGNOSIS: Huntington's Disease ICD-10: G10 (Huntington disease); F02.80 (Dementia in HD without behavioral disturbance); F02.81 (Dementia in HD with behavioral disturbance)

CPT CODES: 81401 (Huntington gene test (HTT CAG repeat)), 85025 (CBC), 80048 (BMP), 80076 (Hepatic panel (LFTs)), 84443 (TSH), 82607 (Vitamin B12), 82306 (Vitamin D, 25-hydroxy), 83540 (Iron studies), 82390 (Ceruloplasmin), 81479 (ACTN3 gene test), 85060 (Acanthocyte screen (peripheral smear)), 80061 (Lipid panel), 84134 (Prealbumin), 83519 (CSF biomarkers (neurofilament light chain)), 82542 (Kynurenine pathway metabolites), 70551 (MRI Brain without contrast), 70553 (MRI Brain volumetric), 93000 (ECG), 95810 (Polysomnography), 78816 (PET imaging (FDG or specific tracers)), 96132 (Neuropsychological testing battery) SYNONYMS: Huntington's chorea, Huntington chorea, HD, hereditary chorea, chronic progressive chorea, Huntington disease, HTT-related disorder SCOPE: Diagnosis confirmation via genetic testing, chorea management, psychiatric symptom treatment, cognitive decline management, dysphagia assessment, genetic counseling, and end-of-life planning. Focuses primarily on outpatient management. Excludes Huntington disease-like syndromes (HDL1-4) and other chorea etiologies.

VERSION: 1.1 CREATED: January 27, 2026 REVISED: January 30, 2026 STATUS: Approved

PRIORITY KEY: STAT = Immediate | URGENT = Within hours | ROUTINE = Standard | EXT = Extended/atypical cases | - = Not applicable to this setting

SECTION A: ACTION ITEMS

1. LABORATORY WORKUP

1A. Essential/Core Labs

Test ED HOSP OPD ICU Rationale Target Finding
Huntington gene test (HTT CAG repeat) (CPT 81401) - ROUTINE ROUTINE - Definitive diagnosis; CAG repeat expansion ≥36 CAG repeats diagnostic (40+ fully penetrant)
CBC (CPT 85025) STAT ROUTINE ROUTINE - Baseline; anemia contributes to fatigue; infection screen Normal
BMP (CPT 80048) STAT ROUTINE ROUTINE - Electrolytes; renal function for medication dosing Normal
Hepatic panel (LFTs) (CPT 80076) - ROUTINE ROUTINE - Baseline before tetrabenazine/deutetrabenazine; valproate if used Normal
TSH (CPT 84443) - ROUTINE ROUTINE - Hypothyroidism can mimic apathy and cognitive slowing Normal
Vitamin B12 (CPT 82607) - ROUTINE ROUTINE - Deficiency can worsen cognitive and psychiatric symptoms >300 pg/mL
Vitamin D, 25-hydroxy (CPT 82306) - ROUTINE ROUTINE - Deficiency common; contributes to falls and bone health >30 ng/mL

1B. Extended Workup (Second-line)

Test ED HOSP OPD ICU Rationale Target Finding
Iron studies (CPT 83540), ferritin (CPT 82728) - ROUTINE ROUTINE - Neurodegeneration with brain iron accumulation if HD-negative Normal
Ceruloplasmin (CPT 82390), serum copper (CPT 82525) - EXT ROUTINE - Wilson's disease if younger onset, HD gene-negative Normal
ACTN3 gene test (CPT 81479) - - EXT - Research; may modify age of onset Research use
Acanthocyte screen (peripheral smear) (CPT 85060) - EXT EXT - Chorea-acanthocytosis if HD gene-negative No acanthocytes
Lipid panel (CPT 80061) - ROUTINE ROUTINE - Cardiovascular risk; weight loss monitoring Normal
Prealbumin (CPT 84134), albumin (CPT 82040) - ROUTINE ROUTINE - Nutritional status assessment in advanced disease Normal

1C. Rare/Specialized (Refractory or Atypical)

Test ED HOSP OPD ICU Rationale Target Finding
Genetic testing for HDL syndromes (PRNP, JPH3, TBP, ATN1) (CPT 81479) - - EXT - HD-like phenotype with negative HTT test Identifies HD-like syndrome
CSF biomarkers (neurofilament light chain) (CPT 83519) - - EXT - Disease progression monitoring; research Elevated in active disease
Kynurenine pathway metabolites (CPT 82542) - - EXT - Research; therapeutic target assessment Research use

2. DIAGNOSTIC IMAGING & STUDIES

2A. Essential/First-line

Study ED HOSP OPD ICU Timing Target Finding Contraindications
MRI Brain without contrast (CPT 70551) URGENT ROUTINE ROUTINE - At diagnosis Caudate atrophy; lateral ventricle enlargement ("boxcar" ventricles) MRI-incompatible devices

2B. Extended

Study ED HOSP OPD ICU Timing Target Finding Contraindications
MRI Brain volumetric (CPT 70553) - - ROUTINE - Baseline and annually for progression Quantify caudate and striatal volume loss MRI contraindications
Swallowing evaluation (VFSS or FEES) (CPT 74230/92612) - ROUTINE ROUTINE - At diagnosis and with dysphagia symptoms Identify aspiration risk; guide diet modification None
ECG (CPT 93000) - ROUTINE ROUTINE - Baseline before tetrabenazine/deutetrabenazine QTc <450 ms None
Polysomnography (CPT 95810) - - ROUTINE - Sleep disturbance evaluation Rule out sleep apnea; assess sleep architecture None

2C. Rare/Specialized

Study ED HOSP OPD ICU Timing Target Finding Contraindications
PET imaging (FDG or specific tracers) (CPT 78816) - - EXT - Research; atypical presentation Striatal hypometabolism None
Neuropsychological testing battery (CPT 96132) - - ROUTINE - At diagnosis and annually Baseline cognitive profile; monitor decline None
Genetic modifier testing (research) (CPT 81479) - - EXT - Prognosis; clinical trials Identifies modifiers of age of onset None

3. TREATMENT

3A. Acute/Emergent

Treatment Route Indication Dosing Contraindications Monitoring ED HOSP OPD ICU
Lorazepam IV/PO Severe chorea causing injury or exhaustion 0.5 mg :: IV/PO :: PRN :: 0.5-2 mg IV/PO q4-6h PRN; short-term use only Respiratory depression; acute narrow-angle glaucoma Respiratory status, sedation STAT STAT - STAT
Haloperidol IV/IM Severe psychosis with agitation; acute behavioral emergency 2 mg :: IM :: PRN :: 2-5 mg IM; may repeat q4-6h; max 20 mg/day; transition to oral QTc prolongation; history of NMS; worsens dystonia ECG, EPS, sedation STAT STAT - STAT
Olanzapine IM/PO Acute agitation with psychosis; alternative to haloperidol 5 mg :: IM :: PRN :: 5-10 mg IM; may repeat in 2 hours; max 30 mg/day Concurrent benzodiazepines (caution); diabetes Glucose, sedation, EPS STAT STAT - STAT
IV fluids IV Dehydration from dysphagia or decreased oral intake NS at 75 mL/hr :: IV :: continuous :: NS at 75-125 mL/hr; correct dehydration; transition to oral when safe Fluid overload I/O, electrolytes STAT STAT - STAT
Thiamine IV Nutritional deficiency; altered mental status 100 mg :: IV :: daily :: 100 mg IV daily x 3-5 days; then oral None None STAT STAT - STAT

3B. Symptomatic Treatments - Chorea

Treatment Route Indication Dosing Contraindications Monitoring ED HOSP OPD ICU
Tetrabenazine (Xenazine) PO FDA-approved for HD chorea; first-line 12.5 mg :: PO :: daily :: Start 12.5 mg daily; increase by 12.5 mg q1wk; max 100 mg/day (25 mg per dose); CYP2D6 testing recommended Active suicidality; untreated depression; concurrent MAOIs; hepatic impairment Depression (PHQ-9 monthly), akathisia, parkinsonism, QTc - ROUTINE ROUTINE -
Deutetrabenazine (Austedo) PO FDA-approved for HD chorea; better tolerability than tetrabenazine 6 mg :: PO :: daily :: Start 6 mg daily; increase by 6 mg/wk; max 48 mg/day (24 mg per dose) Active suicidality; untreated depression; concurrent MAOIs; hepatic impairment Depression (PHQ-9 monthly), akathisia, parkinsonism, QTc - ROUTINE ROUTINE -
Valbenazine (Ingrezza) PO Off-label for HD chorea; once daily dosing 40 mg :: PO :: daily :: Start 40 mg daily; may increase to 80 mg after 1 week Severe hepatic impairment; concurrent MAOIs; congenital long QT Depression, akathisia, QTc prolongation - ROUTINE ROUTINE -
Risperidone PO Chorea with psychosis; antipsychotic with motor benefit 0.5 mg :: PO :: daily :: Start 0.5 mg daily; titrate by 0.5 mg q1wk; max 6 mg/day QTc prolongation; history of NMS EPS, metabolic panel, prolactin - ROUTINE ROUTINE -
Olanzapine PO Chorea with weight loss; promotes weight gain 2.5 mg :: PO :: daily :: Start 2.5-5 mg qHS; titrate to effect; typical 5-15 mg/day Diabetes; significant metabolic risk Weight, glucose, lipids - ROUTINE ROUTINE -
Clonazepam PO Adjunct for chorea; also helps myoclonus and anxiety 0.25 mg :: PO :: BID :: Start 0.25 mg BID; titrate slowly; max 4 mg/day Severe respiratory disease; falls risk Sedation, falls, cognitive effects - ROUTINE ROUTINE -
Amantadine PO Mild chorea; may help fatigue 100 mg :: PO :: daily :: Start 100 mg daily; titrate to 100 mg TID; max 400 mg/day End-stage renal disease; seizure history Livedo reticularis, hallucinations, edema - ROUTINE ROUTINE -

3C. Symptomatic Treatments - Psychiatric

Treatment Route Indication Dosing Contraindications Monitoring ED HOSP OPD ICU
Sertraline PO Depression; anxiety; irritability 25 mg :: PO :: daily :: Start 25 mg daily; titrate by 25-50 mg q1-2wk; max 200 mg/day MAOIs within 14 days Suicidality, serotonin syndrome - ROUTINE ROUTINE -
Citalopram PO Depression; anxiety; good tolerability 10 mg :: PO :: daily :: Start 10 mg daily; max 20 mg/day due to QTc risk QTc >500 ms; concurrent QT-prolonging drugs QTc if risk factors - ROUTINE ROUTINE -
Escitalopram PO Depression; anxiety; similar to citalopram 5 mg :: PO :: daily :: Start 5-10 mg daily; max 20 mg/day QTc >500 ms; concurrent QT-prolonging drugs QTc if risk factors - ROUTINE ROUTINE -
Venlafaxine XR PO Depression with fatigue; dual mechanism 37.5 mg :: PO :: daily :: Start 37.5 mg daily; titrate q1wk; max 225 mg/day Uncontrolled hypertension BP at higher doses - ROUTINE ROUTINE -
Mirtazapine PO Depression with insomnia and weight loss; promotes appetite 7.5 mg :: PO :: qHS :: Start 7.5-15 mg qHS; titrate q1-2wk; max 45 mg None significant Weight, sedation - ROUTINE ROUTINE -
Quetiapine PO Psychosis; irritability; insomnia; less EPS than other antipsychotics 25 mg :: PO :: qHS :: Start 25 mg qHS; titrate by 25-50 mg q3d; typical 150-400 mg/day Uncontrolled diabetes Glucose, lipids, QTc - ROUTINE ROUTINE -
Aripiprazole PO Psychosis; irritability; weight-neutral 2 mg :: PO :: daily :: Start 2-5 mg daily; titrate by 5 mg q1wk; max 30 mg/day None significant Akathisia, EPS - ROUTINE ROUTINE -
Lamotrigine PO Mood stabilization; irritability 25 mg :: PO :: daily :: Start 25 mg daily x 2wk; then 50 mg daily x 2wk; titrate by 50 mg q2wk; max 400 mg/day History of severe rash with lamotrigine Rash (SJS risk); slow titration mandatory - ROUTINE ROUTINE -
Valproic acid PO Irritability; aggression; mood stabilization 250 mg :: PO :: BID :: Start 250 mg BID; titrate to level 50-100 mcg/mL Hepatic disease; pregnancy (teratogenic); mitochondrial disease LFTs, ammonia, level, weight - ROUTINE ROUTINE -
Carbamazepine PO Irritability; aggression; alternative mood stabilizer 100 mg :: PO :: BID :: Start 100 mg BID; titrate by 200 mg/wk; target level 4-12 mcg/mL AV block; blood dyscrasias; concurrent MAOIs CBC, LFTs, level, HLA-B*1502 in Asians - ROUTINE ROUTINE -
Buspirone PO Anxiety without sedation; adjunct for irritability 5 mg :: PO :: TID :: Start 5 mg TID; titrate by 5 mg q2-3d; max 60 mg/day Concurrent MAOIs None significant - ROUTINE ROUTINE -

3D. Symptomatic Treatments - Cognitive and Other

Treatment Route Indication Dosing Contraindications Monitoring ED HOSP OPD ICU
Donepezil PO Cognitive impairment; limited evidence in HD 5 mg :: PO :: qHS :: Start 5 mg qHS; may increase to 10 mg after 4-6 weeks GI bleeding; sick sinus syndrome Nausea, bradycardia, diarrhea - ROUTINE ROUTINE -
Rivastigmine PO/Patch Cognitive impairment; alternative to donepezil 1.5 mg :: PO/Patch :: BID :: Start 1.5 mg BID or 4.6 mg patch; titrate monthly Severe hepatic impairment Nausea, weight loss - ROUTINE ROUTINE -
Memantine PO Moderate-severe cognitive impairment; neuroprotective theory 5 mg :: PO :: daily :: Start 5 mg daily; titrate by 5 mg/wk; target 10 mg BID Severe renal impairment (dose adjust) Confusion, constipation - ROUTINE ROUTINE -
Modafinil PO Apathy; excessive daytime sleepiness 100 mg :: PO :: AM :: Start 100 mg each morning; may increase to 200 mg; avoid afternoon dosing Arrhythmias; severe anxiety Insomnia, anxiety, BP - ROUTINE ROUTINE -
Methylphenidate PO Apathy; bradyphrenia; fatigue 5 mg :: PO :: BID :: Start 5 mg at breakfast and lunch; titrate by 5-10 mg q1wk; max 60 mg/day Severe anxiety; psychosis; cardiac arrhythmia HR, BP, appetite, insomnia - ROUTINE ROUTINE -
Trazodone PO Insomnia; irritability; mild sedation 25 mg :: PO :: qHS :: Start 25-50 mg qHS; titrate by 25-50 mg; max 200 mg for sleep Concurrent MAOIs; priapism history Orthostatic hypotension, priapism - ROUTINE ROUTINE -
Melatonin PO Insomnia; circadian rhythm disturbance 3 mg :: PO :: qHS :: Start 3 mg 30 min before bed; may increase to 9 mg None Generally well-tolerated - ROUTINE ROUTINE -
Botulinum toxin (onabotulinumtoxinA) IM Focal dystonia; bruxism; sialorrhea Variable per muscle :: IM :: q12wk :: Dose depends on target muscles; repeat q12 weeks Infection at site; myasthenia gravis Weakness, dysphagia - - ROUTINE -
Glycopyrrolate PO Sialorrhea (drooling) 1 mg :: PO :: BID :: Start 1 mg BID; titrate to effect; max 2 mg TID Glaucoma; urinary retention; GI obstruction Dry mouth, constipation, urinary retention - ROUTINE ROUTINE -
Polyethylene glycol (MiraLAX) PO Constipation (common with reduced mobility and anticholinergics) 17 g :: PO :: daily :: 17 g in 8 oz liquid daily; may increase to BID Bowel obstruction Diarrhea if excessive - ROUTINE ROUTINE -
High-calorie nutritional supplements PO Weight loss; increased metabolic demands 1 can :: PO :: daily :: 1-3 cans (Ensure Plus, Boost Plus) daily between meals None Weight, nutritional markers - ROUTINE ROUTINE -

4. OTHER RECOMMENDATIONS

4A. Referrals & Consults

Recommendation ED HOSP OPD ICU
Huntington Disease Society of America (HDSA) Center of Excellence for comprehensive multidisciplinary care - ROUTINE ROUTINE -
Genetic counselor for pre-test counseling, results disclosure, and family testing discussion - ROUTINE ROUTINE -
Psychiatry for depression, suicidality assessment, irritability, and psychosis management URGENT ROUTINE ROUTINE -
Neuropsychology for baseline and serial cognitive assessment to guide care planning - - ROUTINE -
Speech-language pathology for swallowing evaluation and communication strategies - ROUTINE ROUTINE -
Physical therapy for gait training, fall prevention, and adaptive exercise program - ROUTINE ROUTINE -
Occupational therapy for ADL adaptation, home safety evaluation, and energy conservation - ROUTINE ROUTINE -
Dietitian/nutritionist for weight maintenance strategies and caloric supplementation - ROUTINE ROUTINE -
Social work for caregiver support, disability planning, and community resources - ROUTINE ROUTINE -
Palliative care for symptom management, advance care planning, and goals of care discussions - ROUTINE ROUTINE -
Pulmonology for respiratory assessment in advanced disease and ventilation decisions - ROUTINE ROUTINE -
Gastroenterology for PEG tube placement consideration in advanced dysphagia - ROUTINE ROUTINE -

4B. Patient Instructions

Recommendation ED HOSP OPD
CRITICAL: Report suicidal thoughts immediately as depression is common and treatable in HD STAT STAT ROUTINE
Do not drive if experiencing significant chorea, cognitive impairment, or sedating medication effects URGENT ROUTINE ROUTINE
Maintain high caloric intake (3000-4000 kcal/day may be needed) due to hypermetabolic state - ROUTINE ROUTINE
Eat slowly, take small bites, and remain upright 30 minutes after meals to reduce aspiration risk - ROUTINE ROUTINE
Complete advance directive and healthcare power of attorney while capacity is preserved - ROUTINE ROUTINE
Inform all healthcare providers about HD as many common medications can worsen symptoms - ROUTINE ROUTINE
First-degree relatives have 50% risk; genetic counseling available but genetic testing is a personal choice - ROUTINE ROUTINE
Avoid alcohol which worsens balance, cognition, and interacts with medications - ROUTINE ROUTINE

4C. Lifestyle & Prevention

Recommendation ED HOSP OPD
Regular aerobic exercise (walking, swimming, stationary bike) improves motor function and mood - ROUTINE ROUTINE
Fall prevention: remove home hazards, adequate lighting, grab bars, non-slip surfaces - ROUTINE ROUTINE
Maintain social engagement and meaningful activities to reduce depression and apathy - ROUTINE ROUTINE
Cognitive engagement through puzzles, reading, and structured activities may help maintain function - ROUTINE ROUTINE
Structure daily routine with consistent timing for medications, meals, and activities - ROUTINE ROUTINE
Caregiver respite and support groups essential to prevent caregiver burnout - ROUTINE ROUTINE
Smoking cessation to reduce aspiration pneumonia risk and cardiovascular disease - ROUTINE ROUTINE
Limit caffeine if insomnia or anxiety are problematic - ROUTINE ROUTINE

SECTION B: REFERENCE

5. DIFFERENTIAL DIAGNOSIS

Alternative Diagnosis Key Distinguishing Features Tests to Differentiate
Huntington disease-like 1 (HDL1) Prion protein gene mutation; similar phenotype PRNP gene testing
Huntington disease-like 2 (HDL2) African ancestry; JPH3 gene mutation JPH3 gene testing
Spinocerebellar ataxia 17 (HDL4) Prominent ataxia; TBP gene expansion TBP gene testing
Chorea-acanthocytosis Orolingual dystonia; self-mutilation; acanthocytes Peripheral smear; VPS13A gene testing
McLeod syndrome X-linked; cardiomyopathy; elevated CK Kell antigen typing; XK gene testing
Sydenham chorea Post-streptococcal; younger patients; self-limited ASO titer; anti-DNAse B
Benign hereditary chorea Childhood onset; non-progressive; NKX2-1 mutation NKX2-1 gene testing; family history
Wilson's disease Younger onset; Kayser-Fleischer rings; hepatic disease Ceruloplasmin; 24-hr urine copper; slit lamp
Neuroacanthocytosis Peripheral neuropathy; seizures; elevated CK Peripheral smear; genetic testing
Tardive dyskinesia Antipsychotic exposure; orobuccal predominant Medication history; AIMS scale
Anti-NMDA receptor encephalitis Psychiatric symptoms; seizures; dyskinesias NMDA receptor antibodies; CSF analysis

6. MONITORING PARAMETERS

Parameter Frequency Target/Threshold Action if Abnormal ED HOSP OPD ICU
UHDRS (Unified Huntington's Disease Rating Scale) Every 6-12 months Document trend; track motor progression Adjust medications; update care plan - - ROUTINE -
Depression screening (PHQ-9) Every visit; monthly if on VMAT2 inhibitor PHQ-9 <5 Intensify antidepressant; psychiatry referral if PHQ-9 >15 URGENT ROUTINE ROUTINE -
Suicidality assessment Every visit No active suicidal ideation Immediate psychiatric evaluation; safety planning STAT STAT ROUTINE -
Cognitive assessment (MoCA or MMSE) Every 6-12 months Document trend Update care planning; capacity assessment - - ROUTINE -
Weight Every visit Stable or increasing Increase caloric intake; dietitian referral - ROUTINE ROUTINE -
Swallowing function Annually or if symptoms No aspiration Modify diet texture; speech therapy; PEG consideration - ROUTINE ROUTINE -
ECG (if on VMAT2 inhibitor) Baseline and with dose changes QTc <500 ms Hold medication if QTc >500 ms; reduce dose - ROUTINE ROUTINE -
Functional independence (TFC) Every 6-12 months Document functional stage Adjust level of care; advance care planning - - ROUTINE -
Caregiver burden assessment Annually Sustainable caregiving Respite care; support resources - ROUTINE ROUTINE -
Falls frequency Each visit Zero falls PT referral; home safety; medication review - ROUTINE ROUTINE -

7. DISPOSITION CRITERIA

Disposition Criteria
Discharge home Stable psychiatric status; adequate oral intake; safe swallowing; caregiver available; outpatient follow-up arranged
Admit to floor Severe psychiatric symptoms requiring stabilization; aspiration pneumonia; significant weight loss requiring evaluation; severe chorea causing exhaustion or injury
Admit to ICU Aspiration with respiratory failure; severe rhabdomyolysis from chorea; neuroleptic malignant syndrome; suicidal attempt requiring medical stabilization
Skilled nursing facility Advanced disease; 24-hour care needs; dysphagia requiring supervision; frequent falls; caregiver unable to provide required care
Hospice referral End-stage disease (TFC stage 5); recurrent aspiration; patient/family goals favor comfort care

8. EVIDENCE & REFERENCES

Recommendation Evidence Level Source
Tetrabenazine reduces chorea in HD Class I, Level A Huntington Study Group. Neurology 2006
Deutetrabenazine reduces chorea with improved tolerability Class I, Level A Huntington Study Group. JAMA 2016
CAG repeat length inversely correlates with age of onset Class II, Level B Andrew et al. Nat Genet 1993
AAN practice parameter for HD treatment Guideline Armstrong & Miyasaki. Neurology 2012
High suicide rate in HD requires screening Class II, Level B Paulsen et al. J Neuropsychiatry Clin Neurosci 2005
UHDRS reliable for tracking disease progression Class II, Level A Huntington Study Group. Mov Disord 1996
CYP2D6 genotype affects tetrabenazine metabolism Class II, Level B Xenazine FDA prescribing information 2008
Genetic counseling improves outcomes in at-risk individuals Class II, Level B Tibben. Handb Clin Neurol 2007
Dysphagia common and associated with aspiration risk Class II, Level C Heemskerk & Roos. Dysphagia 2011
Multidisciplinary care improves outcomes Class III, Level C Veenhuizen & Bherer. J Huntingtons Dis 2017
Exercise benefits motor and cognitive function Class II, Level B Quinn et al. Cochrane Database Syst Rev 2022
Valbenazine effective for hyperkinetic movements Class I, Level A Hauser et al. JAMA Neurol 2017

CHANGE LOG

v1.1 (January 30, 2026) - Reformatted lab tables (1A/1B/1C) to standard column order: Test | ED | HOSP | OPD | ICU | Rationale | Target Finding - Reformatted imaging tables (2A/2B/2C) to standard column order: Study | ED | HOSP | OPD | ICU | Timing | Target Finding | Contraindications - Added inline CPT codes to all lab tests and imaging studies - Fixed structured dosing format: starting dose only in first field across all treatment sections - Expanded cross-references ("Same as tetrabenazine", "Same as citalopram") with actual content - Added clinical synonyms for searchability - Expanded ICD-10 codes (added F02.80, F02.81) - Added VERSION/CREATED/REVISED header block

v1.0 (January 27, 2026) - Initial template creation - Comprehensive coverage of chorea management with VMAT2 inhibitors - Psychiatric symptom management with multiple drug classes - Genetic testing and counseling guidance - Dysphagia and nutritional support - End-of-life and palliative care considerations - Structured dosing format for order sentence generation

APPENDIX A: Huntington's Disease Staging

Stage TFC Score Functional Status Care Needs
Stage 1 (Early) 11-13 Engaged in occupation; handles finances; performs all ADLs Independent; outpatient monitoring
Stage 2 (Early-Intermediate) 7-10 Reduced work capacity; handles daily affairs with minimal assistance Minimal assistance; may need supervision for complex tasks
Stage 3 (Intermediate) 3-6 Unable to work; requires help with finances; still manages basic ADLs Moderate assistance; partial supervision
Stage 4 (Late-Intermediate) 1-2 Requires assistance with most ADLs; can live at home with care Substantial assistance; may need skilled care
Stage 5 (Advanced) 0 Total dependence; requires full care Total care; nursing facility or hospice

APPENDIX B: Genetic Counseling Considerations

Pre-Test Counseling Essentials

  1. Implications of positive result: Progressive, fatal disease with no cure; 50% risk to offspring
  2. Implications of negative result: No increased risk, but survivor guilt possible
  3. Intermediate alleles (27-35 repeats): Not affected, but may expand in offspring
  4. Reduced penetrance (36-39 repeats): May or may not develop HD; difficult counseling
  5. Full penetrance (40+ repeats): Will develop HD if lives long enough
  6. Insurance and discrimination: GINA protects health insurance and employment; does NOT cover life, disability, or long-term care insurance
  7. Timeline: Results typically 2-4 weeks; follow-up support essential

Testing of At-Risk Individuals

  • Minimum age 18 for predictive testing (legal adult)
  • Do not test minors unless symptomatic
  • Recommended: 2+ counseling sessions before testing
  • Wait period between disclosure and decision
  • Support system should be in place before results

Prenatal Testing Options

  1. Prenatal diagnosis: CVS at 10-12 weeks or amniocentesis at 15-20 weeks
  2. Preimplantation genetic testing (PGT): IVF with embryo selection
  3. Non-disclosure testing: Pregnancy terminated if affected without revealing parent's status
  4. Exclusion testing: Determines if fetus inherited grandparent's chromosome without revealing parent's status

APPENDIX C: End-of-Life Planning

Advance Directive Considerations Specific to HD

Issue Considerations
Feeding tubes PEG may prolong survival but not necessarily quality of life; discuss before capacity lost
Mechanical ventilation Usually not consistent with comfort goals in end-stage HD
Antibiotic use Consider limiting to comfort measures in advanced disease
Hospitalization May prefer comfort care at home or hospice facility
Autopsy/brain donation Important for research; discuss while patient can consent

Hospice Eligibility Criteria (General Guidance)

  • TFC Stage 5 (Total Functional Capacity score 0)
  • Unable to ambulate without substantial assistance
  • Unable to communicate intelligibly
  • Recurrent aspiration pneumonia
  • PPS (Palliative Performance Scale) ≤50%
  • Significant weight loss despite nutritional support