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derm.herpes-zoster.core.v1

Herpes zoster (shingles) — acute reactivation, complications & PHN

dermatologyacuteadultgeriatricacuteoutpatient
Start encounter →Print handoutPRODUCTION

Dermatology-framed acute zoster engine (shard-06 Phase C gap-fill 2026-05-17). Owns rash recognition → 72-h antiviral timing → complication red-flags → PHN ladder → RZV handoff. Deliberately distinct from id.varicella-zoster.v1 (untouched), which is the lifespan/vaccine-prevention VZV engine; this engine is the skin-first acute companion and cross-references the ID engine for disseminated/visceral disease. Cross-dossier routing: HZO → ophtho.uveitis.core.v1 / ophtho.acute-red-eye.core.v1 (authored this shard); Ramsay Hunt → neuro.bell-palsy.v1 (exists); disseminated/visceral/CNS → id.sepsis.core.v1 / immunocompromised pathway. RxCUIs validated via public RxNav 2026-05-17 (CUI→name): acyclovir 281, valacyclovir 73645, famciclovir 68099, gabapentin 25480, pregabalin 187832, amitriptyline 704, nortriptyline 7531, lidocaine 5% patch 1745091, prednisone 8640, RZV/Shingrix gE antigen 1986820. Initial valacyclovir/famciclovir/lidocaine-patch CUIs were corrected after RxNav lookup. Registry wiring (src/lib/dossiers/_registry.ts, panel router/index) is shared state owned by the orchestrator and intentionally NOT edited here per shard contract; the dossier file is contract-valid for INTEGRATED and will pass dossier:audit/contract test once collated. Co-located authority docs: derm.herpes-zoster.core.v1._design-brief.md + derm.herpes-zoster.core.v1._research-bundle.md (≥14 PMIDs, ≥6 effect-sizes, Bayesian LR table, sibling differentiation, special-pop branches).

Entry points (4)

  • symptom
    Unilateral grouped vesicles on erythematous base in a single dermatome, not crossing midline (Cohen NEJM 2013 — pathognomonic; Dworkin CID 2007)
    unilateral_dermatomal_vesicular_rash
  • symptom
    Burning/lancinating dermatomal pain or dysaesthesia preceding rash by 1–5 days (Cohen NEJM 2013 — preherpetic neuralgia)
    dermatomal_prodromal_pain
  • symptom
    V1 (ophthalmic) rash, eyelid involvement, or vesicle on nasal tip/side (Hutchinson sign) (Liesegang Ophthalmology 2008 — HZO emergency)
    periorbital_v1_rash_or_nasal_tip
  • symptom
    Vesicles in the ear canal/auricle/oral mucosa + peripheral facial palsy ± vertigo/hearing loss (Ramsay Hunt) (Sweeney JNNP 2001)
    ear_vesicles_with_facial_weakness

Required inputs (14)

  • rash_distributionrequired
    symptom • used at ENTRY
    Single-dermatome vs multidermatomal/disseminated drives immunocompromise workup and IV-vs-PO decision (Cohen NEJM 2013; Dworkin CID 2007)
  • rash_onset_hoursrequired
    symptom • used at ENTRY
    Antiviral benefit is greatest within 72 h of rash onset; ongoing new-vesicle formation extends the treatment window (Dworkin CID 2007 — T_treat anchor)
  • v1_dermatome_or_hutchinsonrequired
    symptom • used at RED_FLAGS
    Trigeminal V1 / nasociliary (Hutchinson) involvement = ocular-threatening → emergent ophthalmology (Liesegang Ophthalmology 2008; AAO HZO PPP)
  • ocular_pain_redness_vision_changerequired
    symptom • used at RED_FLAGS
    Keratitis/uveitis/acute retinal necrosis risk in HZO — vision-threatening (AAO HZO PPP; Liesegang 2008)
  • facial_palsy_or_otalgiarequired
    symptom • used at RED_FLAGS
    Ramsay Hunt: peripheral CN VII palsy + ear vesicles; worse recovery than Bell palsy without prompt antiviral+steroid (Sweeney JNNP 2001)
  • cns_featuresrequired
    symptom • used at RED_FLAGS
    Headache, confusion, focal deficit, meningismus → VZV encephalitis/meningitis/vasculopathy → LP + IV acyclovir (Gershon 2015)
  • immunocompromiserequired
    history • used at CONTEXT
    HIV/transplant/chemo/high-dose steroid/biologic → disseminated & visceral risk; lower threshold for IV acyclovir + admission (Cohen NEJM 2013; Dworkin CID 2007)
  • agerequired
    demographic • used at CONTEXT
    Age ≥50 (esp. ≥60) is the dominant PHN risk factor and RZV-eligibility driver (Lal NEJM 2015; Dooling MMWR 2018)
  • pregnancy_status
    demographic • used at CONTEXT
    Acyclovir/valacyclovir preferred antivirals in pregnancy; avoid gabapentinoid/TCA first-line; RZV deferred (CDC; ACOG)
  • pain_severity_nrsrequired
    symptom • used at CONTEXT
    Baseline 0–10 pain score anchors acute analgesia ladder and PHN trajectory monitoring (Dworkin CID 2007)
  • pain_duration_post_rash
    symptom • used at FOLLOWUP
    Pain persisting ≥90 days after rash onset defines PHN and triggers the neuropathic ladder (Dworkin CID 2007)
  • vzv_pcr
    lab • used at INITIAL_WORKUP
    Lesion-swab VZV PCR confirms atypical/disseminated/immunocompromised or HZO/Ramsay Hunt cases (Cohen NEJM 2013 — highest-yield test)
  • creatininerequired
    lab • used at TREATMENT
    Acyclovir/valacyclovir/famciclovir + gabapentinoid renal dose adjustment; IV acyclovir crystal nephropathy risk (Dworkin CID 2007)
  • hiv_status_unknown
    history • used at BRANCHING_WORKUP
    Zoster in a younger adult or multidermatomal disease is an HIV-indicator condition — offer HIV testing (CDC)

12-phase flow (12)

  1. 1FRAME
    Acute zoster reactivation, skin-first: confirm dermatomal vesicular rash, decide antiviral timing, screen complications, and pre-set the PHN-prevention + RZV-handoff arc (Cohen NEJM 2013; Dworkin CID 2007). Disseminated/visceral routes to id.sepsis.core.v1 / immunocompromised pathway; ocular to ophtho.*; oticus to neuro.bell-palsy.v1
    advance: scope confirmed; lifespan-VZV/vaccine overlap delegated to id.varicella-zoster.v1
  2. 2ENTRY
    Recognise unilateral grouped vesicles in a single dermatome (not crossing midline) ± prodromal neuritic pain; capture rash-onset hours for the 72-h window (Cohen NEJM 2013 — clinical diagnosis; Dworkin CID 2007)
    inputs: rash_distribution, rash_onset_hours
    advance: dermatomal pattern + onset time established
  3. 3CONTEXT
    Host & risk drivers — age (PHN/RZV), immunocompromise (dissemination), pregnancy (antiviral selection), baseline pain NRS (Cohen NEJM 2013; Dworkin CID 2007; Lal NEJM 2015)
    inputs: immunocompromise, age, pregnancy_status, pain_severity_nrs
    advance: host risk profile assigned
  4. 4RED_FLAGS
    Emergent screens: V1/Hutchinson + ocular symptoms → ophthalmology now; ear vesicles + facial palsy → Ramsay Hunt; >2 non-contiguous dermatomes / visceral / CNS → disseminated VZV (Liesegang 2008; Sweeney 2001; Gershon 2015)
    inputs: v1_dermatome_or_hutchinson, ocular_pain_redness_vision_change, facial_palsy_or_otalgia, cns_features
    actions: workup.acute_vision_loss, workup.bells_palsy, calc.news2
    advance: complication red flags screened and routed
  5. 5INITIAL_WORKUP
    Zoster is a clinical diagnosis in classic cases; lesion-swab VZV PCR (DFA backup) for atypical/disseminated/immunocompromised/HZO/Ramsay Hunt; CBC + renal for antiviral dosing & host assessment (Cohen NEJM 2013; Dworkin CID 2007)
    inputs: vzv_pcr, creatinine
    actions: panel.cbc, panel.renal
    advance: diagnosis confirmed clinically or by PCR; renal function known for dosing
  6. 6BRANCHING_WORKUP
    PHN-risk neuropathic-pain branch; HIV testing if young/atypical/multidermatomal; LP if CNS features; ophthalmology slit-lamp if HZO; audiometry/ENT if Ramsay Hunt (CDC; Gershon 2015; AAO HZO PPP)
    inputs: hiv_status_unknown
    actions: workup.peripheral_neuropathy, workup.chronic_pruritus
    advance: targeted complication workup launched per phenotype
  7. 7DIFFERENTIAL
    Zosteriform HSV (recurrent, smaller cluster, PCR-typed), contact/allergic dermatitis (pruritic, exposure-patterned, non-dermatomal), early cellulitis/erysipelas (no vesicles, warmth, systemic), bullous impetigo, insect bites, dermatomal pain mimics (MI/biliary/renal colic before rash) (Cohen NEJM 2013)
    advance: mimics excluded; zoster confirmed
  8. 8RISK_STRATIFICATION
    Stratify: immunocompetent localized (PO antiviral, outpatient) vs ocular/oticus/CNS (specialist + admit consider) vs disseminated/immunocompromised (IV acyclovir, admit); PHN risk by age + acute pain severity + ophthalmic site (Dworkin CID 2007; Cohen NEJM 2013)
    inputs: age, immunocompromise, pain_severity_nrs
    actions: calc.news2
    advance: severity tier + disposition pre-set
  9. 9TREATMENT
    Antiviral within 72 h (or while new vesicles forming): valacyclovir 1 g PO TID ×7 d (preferred) / famciclovir 500 mg PO TID / acyclovir 800 mg PO 5×/day; IV acyclovir 10 mg/kg q8h for disseminated/visceral/CNS/severe-immunocompromised/sight-threatening HZO; acute pain control; adjunctive prednisone only in selected immunocompetent (e.g., Ramsay Hunt, severe pain) — NOT for PHN prevention; eye care via ophthalmology for HZO (Dworkin CID 2007; Wood NEJM 1994; Beutner AAC 1995; Tyring 2000)
    inputs: creatinine
    advance: antiviral started with correct renal dose, analgesia titrated, specialist co-management arranged
  10. 10DISPOSITION
    Outpatient: immunocompetent localized non-ophthalmic, reliable, oral-tolerant. Admit/transfer: sight-threatening HZO, disseminated/visceral, CNS, severe immunocompromise, intractable pain, unable to take PO (Cohen NEJM 2013; Liesegang 2008; Gershon 2015)
    inputs: immunocompromise
    advance: disposition documented with specialist routing
  11. 11MONITORING
    Reassess rash crusting (~7–10 d), pain trajectory, antiviral tolerance/renal function; HZO → serial ophthalmology; Ramsay Hunt → House-Brackmann grading + audiometry; watch for dissemination if immunocompromised (Dworkin CID 2007; AAO HZO PPP)
    inputs: pain_severity_nrs, creatinine
    actions: panel.renal
    advance: rash healing and pain trend established; complications co-managed
  12. 12FOLLOWUP
    PHN screen at ≥90 d (gabapentin/pregabalin → TCA (nortriptyline) → lidocaine 5% patch → capsaicin/opioid escalation); secondary prevention: 2-dose RZV (Shingrix) ≥50 routine and ≥19 immunocompromised — administer after acute episode resolves (Dworkin CID 2007; Rice Pain 2001; Dworkin Pain 2003; Dooling MMWR 2018; Anderson MMWR 2022)
    inputs: pain_duration_post_rash
    actions: workup.peripheral_neuropathy
    advance: PHN plan + RZV handoff documented