Clinical Commander

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rheum.gca.chronic.v1

Giant cell arteritis (GCA / temporal arteritis)

rheumatologyacutechronicadultgeriatricacuteoutpatient
Start encounter →Print handoutPRODUCTION

Manifest is a Batch-23 scaffold — atoms / phenotypes / regimen drug list not yet authored. Regimen axis intentionally empty — prednisone / tocilizumab / methotrexate / aspirin require manifest backing. Large-vessel GCA phenotype + steroid taper protocols need dedicated phenotype axes when manifest splits them.

Entry points (6)

  • symptom
    New-onset headache in patient ≥50 (ACR 2021 classification criterion)
    new_onset_headache_age_50plus
  • symptom
    Jaw claudication (highest LR+ for GCA — ACR 2021)
    jaw_claudication
  • symptom
    Amaurosis fugax / acute visual loss (ACR 2021 / EULAR 2023 — IV pulse indication)
    transient_or_persistent_visual_loss
  • symptom
    Scalp tenderness or temporal artery abnormality (ACR 2021)
    scalp_tenderness
  • lab_abnormality
    Markedly elevated ESR or CRP in elderly patient (ACR 2021 / BSR 2020)
    esr_crp_marked_elevation
  • problem_list
    Polymyalgia rheumatica with cranial features (ACR 2021 — GCA coexists in 15-20% of PMR)
    pmr_with_cranial_features

Required inputs (12)

  • agerequired
    demographic • used at CONTEXT
    GCA essentially restricted to age ≥50 (ACR 2021 classification criterion); rare under 60
  • visual_symptomsrequired
    symptom • used at RED_FLAGS
    Visual loss is irreversible — STAT high-dose steroids before biopsy (ACR 2021 / EULAR 2023 strong recommendation)
  • jaw_claudication_qualityrequired
    symptom • used at CONTEXT
    Strongest LR+ for GCA among presenting features (Smetana JAMA 2002 meta-analysis)
  • pmr_features
    symptom • used at CONTEXT
    PMR present in 40-50% of GCA (BSR 2020); informs treatment + prognosis
  • esrrequired
    lab • used at INITIAL_WORKUP
    Often >50 mm/h (ACR 2021); trend on therapy
  • crprequired
    lab • used at INITIAL_WORKUP
    More sensitive than ESR (BSR 2020); key trend marker — CRP suppressed by tocilizumab independent of disease (GiACTA Stone 2017)
  • cbcrequired
    lab • used at INITIAL_WORKUP
    Normocytic anemia + thrombocytosis common (BSR 2020)
  • lft
    lab • used at INITIAL_WORKUP
    Mild AST/ALK-P elevation common (BSR 2020); baseline for steroid + tocilizumab hepatotoxicity monitoring
  • a1c
    lab • used at TREATMENT
    Steroid-induced diabetes baseline (ACR 2017 GIO guideline)
  • temporal_artery_biopsyrequired
    imaging • used at INITIAL_WORKUP
    Gold standard — perform within 14 days of starting steroids (ACR 2021); segmental skip lesions → 1-2 cm sample (BSR 2020)
  • temporal_artery_us_or_mri
    imaging • used at INITIAL_WORKUP
    Halo sign on color Doppler / MRI vessel-wall enhancement; EULAR 2018/2023 fast-track imaging path
  • aortic_imaging
    imaging • used at BRANCHING_WORKUP
    Large-vessel GCA (PET-CT / MRA / CTA aorta) — up to 50% have aortic involvement (ACR 2021 / EULAR 2018)

12-phase flow (12)

  1. 1FRAME
    Adult GCA (cranial + large-vessel phenotypes per ACR 2021). PMR-only without cranial / vascular features routed separately
    inputs: age
    advance: scope confirmed
  2. 2ENTRY
    Recognise cranial features in age ≥50 (ACR 2021); PMR with new headache; sudden visual symptoms
    advance: entry trigger present
  3. 3CONTEXT
    Risk factors (PMR coexistence 40-50% — BSR 2020; female, northern European, age ≥50), comorbidities for steroid-related risk, fall risk, osteoporosis
    inputs: jaw_claudication_quality, pmr_features
    advance: risk profile captured
  4. 4RED_FLAGS
    Visual loss (transient or persistent), CRAO, diplopia, stroke-like symptoms, severe constitutional decline → STAT IV pulse methylprednisolone before biopsy (ACR 2021 / EULAR 2023 strong)
    inputs: visual_symptoms
    advance: red flags addressed; ophthalmology / neuro engaged
  5. 5INITIAL_WORKUP
    ESR + CRP + CBC + LFT + creatinine immediately; temporal artery US or MRI (EULAR 2018 fast-track); biopsy within 14 days (ACR 2021); do NOT delay steroids waiting for biopsy (ACR 2021 / BSR 2020)
    inputs: esr, crp, cbc, temporal_artery_biopsy
    actions: panel.inflammation, panel.cbc
    advance: workup ordered + steroids started
  6. 6BRANCHING_WORKUP
    Aortic + large-vessel imaging if persistent symptoms / atypical biopsy / suspected LV-GCA (EULAR 2018 — PET-CT / MRA / CTA); bone densitometry baseline (ACR 2017 GIO); PMR overlap workup
    inputs: aortic_imaging
    advance: extracranial mapping complete
  7. 7DIFFERENTIAL
    CRAO non-arteritic AION, migraine, tension headache, sinusitis, infection, malignancy, ANCA vasculitis, Takayasu (younger — ACR 2021), atherosclerotic disease
    advance: mimics excluded
  8. 8RISK_STRATIFICATION
    Cranial-only vs LV-GCA phenotype (ACR 2021); relapse risk (GiACTA Stone 2017 — ~50% relapse on taper); steroid-toxicity risk profile
    advance: phenotype + relapse risk assigned
  9. 9TREATMENT
    Without visual symptoms: prednisone 40-60 mg PO daily (ACR 2021 / EULAR 2023) until symptoms + CRP normalize. With visual symptoms / amaurosis fugax: IV methylprednisolone 500-1000 mg × 3 d → high-dose oral (ACR 2021 strong). Tocilizumab 162 mg SC weekly (or q2wk) for steroid-sparing — Class I (GiACTA Stone NEJM 2017; ACR 2021 + EULAR 2023 strong). Methotrexate alternative steroid-sparer when tocilizumab unavailable (EULAR 2023 conditional). Aspirin 81 mg daily (EULAR 2018 — cardiovascular + ophthalmic protection). Calcium + vitamin D + bisphosphonate for steroid-induced osteoporosis (ACR 2017 GIO). PJP prophylaxis if pred ≥20 mg ≥4 weeks. Slow taper over 18-24 months (BSR 2020 / EULAR 2023)
    inputs: a1c, lft
    advance: induction regimen + adjuncts started
  10. 10DISPOSITION
    Outpatient unless visual symptoms, stroke-like features, or unable to tolerate oral steroids (ACR 2021)
    inputs: visual_symptoms
    advance: level of care set
  11. 11MONITORING
    Symptom + ESR/CRP at 2-4 weeks, then monthly during taper (BSR 2020). Watch for tocilizumab-blunted CRP — rely on symptoms + ESR (GiACTA Stone 2017). DEXA at baseline + annually (ACR 2017 GIO). Glucose monitoring weekly during high-dose steroids
    inputs: esr, crp, a1c
    actions: panel.inflammation
    advance: response confirmed
  12. 12FOLLOWUP
    Slow steroid taper to ≤5 mg by 12 months when feasible (BSR 2020 / EULAR 2023); aortic surveillance imaging q1-2 years if LV-GCA (EULAR 2018); relapse education + return-precaution counseling
    advance: long-term management plan documented