What is the likely diagnosis and treatment for a 91-year-old male with a severe headache, markedly elevated erythrocyte sedimentation rate (ESR), and hypoxia, despite a negative head computed tomography (CT) scan?

Giant Cell Arteritis (GCA) with Pulmonary Involvement

This 91-year-old male with severe headache, markedly elevated ESR, and hypoxia despite negative head CT most likely has giant cell arteritis (GCA), and you must initiate high-dose glucocorticoid therapy immediately without waiting for temporal artery biopsy results. 1

Diagnosis

Why GCA is the Primary Diagnosis

• Age and presentation are classic: A 91-year-old with severe headache and markedly elevated ESR has GCA until proven otherwise 2
• ESR >100 mm/h has 92.2% specificity for GCA with a positive likelihood ratio of 3.11 2
• Negative head CT does not exclude GCA: CT is used to rule out subarachnoid hemorrhage or mass lesions, not to diagnose vasculitis 1
• Hypoxia suggests large vessel involvement: GCA can affect the aorta and its branches, potentially causing pulmonary complications through thoracic aortic involvement 1

Critical Clinical Features to Assess Immediately

• New-onset localized headache (typically temporal) 2
• Jaw claudication (pain with chewing) - highly specific for GCA 2, 3
• Visual symptoms (blurred vision, diplopia, amaurosis fugax) - indicates impending vision loss 4
• Scalp tenderness over temporal arteries 4
• Constitutional symptoms (fever, weight loss, malaise) 2
• Temporal artery abnormalities on palpation (tenderness, decreased pulse, nodularity) 1

Diagnostic Workup

• C-reactive protein (CRP): Should be obtained immediately as it typically correlates with ESR in GCA 2, 5
• Complete blood count: Look for anemia and thrombocytosis, common in GCA 2
• Temporal artery biopsy should be performed but must not delay treatment 1
• Chest imaging: Given the hypoxia, obtain chest X-ray or CT to evaluate for pulmonary pathology and assess for thoracic aortic involvement 1

Immediate Treatment Protocol

High-Dose Glucocorticoid Therapy

Start prednisone 60 mg daily (or equivalent IV methylprednisolone if unable to take oral) immediately 1, 6, 4

• Do not wait for temporal artery biopsy results - biopsy can be performed within 1-2 weeks of starting steroids without affecting diagnostic yield 1
• Symptoms typically improve dramatically within 24-48 hours if GCA is present 6
• Failure to improve should prompt reconsideration of diagnosis 6

Low-Dose Aspirin

Add aspirin 75-150 mg daily to reduce risk of cardiovascular and cerebrovascular events 1

• Consider gastroduodenal protection (proton pump inhibitor) when starting aspirin 1

Temporal Artery Biopsy

• Perform within 1-2 weeks of starting steroids 1
• Contralateral biopsy is not routinely indicated 1
• Negative biopsy does not rule out GCA when clinical suspicion is high with elevated inflammatory markers 4, 3

Critical Pitfalls to Avoid

Do Not Delay Treatment

• Vision loss from GCA is irreversible - arteritic anterior ischemic optic neuropathy (AAION) can occur suddenly 4
• Risk of second eye involvement is high without treatment 4
• Stroke can be an atypical presentation of GCA, particularly in posterior circulation 5

Do Not Rely Solely on ESR Criteria

• GCA can occur with ESR <50 mm/h in 4-15% of cases 6, 3
• GCA with normal ESR and CRP occurs in approximately 0.8% of cases 3
• Clinical suspicion should drive treatment decisions, not laboratory values alone 6, 4, 3

Alternative Diagnoses to Consider

Given the combination of severe headache, elevated ESR, and hypoxia, also consider:

• Intracranial infection (sphenoid sinus abscess with intracranial extension, cerebral venous thrombosis) - can present with headache and elevated ESR 7
• Infective endocarditis - obtain blood cultures if fever is present 2
• Malignancy - can cause elevated ESR and constitutional symptoms 2

However, the age, presentation, and markedly elevated ESR make GCA the most likely diagnosis requiring immediate treatment 2, 5

Monitoring and Follow-up

• Clinical response should occur within 24-48 hours 6
• Monitor ESR and CRP to assess treatment response, though clinical improvement is more important 1
• Relapse is usually associated with rising ESR 1
• Slow steroid taper over months once disease is controlled 6
• Consider adjunctive immunosuppression (methotrexate, azathioprine) to facilitate steroid reduction 1