A 62-year-old woman with a 2-month history of progressive headache, jaw claudication, visual blurring, and polymyalgia rheumatica (elevated ESR 95 mm/h, CRP 12 mg/dL) is suspected of having giant cell arteritis (GCA). Temporal artery ultrasound shows a hypoechoic halo sign. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis This patient has **giant cell arteritis (GCA)** with high pretest probability: - Age >60 years - Classic symptoms: headache, jaw claudication, visual symptoms - Polymyalgia rheumatica (present in ~50% of GCA) - Markedly elevated inflammatory markers (ESR 95, CRP 12) - **Temporal artery ultrasound: halo sign** (hypoechoic wall edema—highly specific for GCA) **Key Point:** The halo sign on ultrasound has ~97% specificity for GCA. Combined with clinical features and elevated ESR/CRP, this is sufficient for diagnosis without waiting for biopsy. ## Rationale for Correct Answer **High-Yield:** GCA with visual symptoms (blurring) carries imminent risk of **arteritic anterior ischemic optic neuropathy (AAION)** and permanent blindness. This is a **medical emergency**. 1. **Start high-dose prednisolone 1 mg/kg (60–80 mg/day)** immediately to prevent irreversible vision loss. 2. **Temporal artery biopsy should be arranged within 1–2 weeks** (not before starting therapy) to confirm diagnosis and assess for giant cells and intimal proliferation. 3. **Corticosteroids do not significantly impair biopsy interpretation** if performed within 2 weeks of initiation. **Clinical Pearl:** The risk of vision loss in untreated GCA is ~50% within weeks. Delaying corticosteroids to obtain biopsy first is **contraindicated** when clinical suspicion is high and ultrasound is supportive. ## Why Each Distractor Is Wrong | Option | Reason | |--------|--------| | Biopsy first, then corticosteroids | This **delays critical therapy** and risks permanent blindness. In a patient with visual symptoms and high pretest probability (clinical + ultrasound), starting corticosteroids immediately is standard. Biopsy can follow within 1–2 weeks without compromising diagnostic yield. | | Low-dose prednisolone 20 mg + observation | 20 mg/day is **insufficient** for GCA with visual symptoms. Standard induction is 1 mg/kg (60–80 mg). Underdosing increases risk of AAION and other ischemic complications. | | PET-CT before corticosteroids | PET-CT is useful for assessing **large-vessel involvement** (aorta, subclavian arteries) in GCA, but it is **not a substitute for immediate therapy**. Visual symptoms mandate urgent high-dose corticosteroids regardless of PET findings. Delaying therapy increases blindness risk. | ## Management Algorithm ```mermaid flowchart TD A[Suspected GCA: age >60, headache, jaw claudication, elevated ESR/CRP]:::outcome --> B{Clinical suspicion + imaging findings?}:::decision B -->|High: halo sign on ultrasound OR biopsy-proven| C[Start prednisolone 1 mg/kg immediately]:::action B -->|Moderate: clinical only, no imaging| D[Urgent temporal artery biopsy + start corticosteroids]:::action C --> E[Arrange TAB within 1-2 weeks]:::action D --> E E --> F[Confirm GCA histology]:::outcome F --> G[Taper corticosteroids over 12-24 months]:::action A -->|Visual symptoms present?| H{AAION risk}:::decision H -->|Yes| I[High-dose IV methylprednisolone 500-1000 mg daily x 3 days, then oral prednisolone]:::urgent ``` [cite:Harrison 21e Ch 319]