What is the best course of action for a 46-year-old female patient with recurrent fever, joint pain, hyperthyroidism (previously treated with Methimazole), chronic acid reflux (on Omeprazole), and a history of pneumonia, who is allergic to most painkillers except Paracetamol (acetaminophen)?

Diagnostic Workup and Management

Immediate Diagnostic Priorities

This patient requires urgent evaluation for subacute thyroiditis, which can present with recurrent fever, joint pain, and throat symptoms following viral illness, particularly given her history of hyperthyroidism. 1, 2, 3

Essential Laboratory Tests

• Thyroid function panel: TSH, free T4, and free T3 to assess for thyrotoxic phase of subacute thyroiditis 2, 3
• Inflammatory markers: ESR and CRP (typically markedly elevated in subacute thyroiditis) 4, 5, 2
• Complete blood count: To evaluate for infectious versus inflammatory etiology 5
• Rheumatoid factor and anti-CCP antibodies: To exclude rheumatoid arthritis given the polyarticular joint involvement 6, 4, 5
• Blood cultures: Given the recurrent fever pattern 5

Critical Physical Examination Findings to Assess

• Thyroid palpation: Assess for tenderness, enlargement, or nodularity (anterior neck pain with thyroid tenderness is pathognomonic for subacute thyroiditis) 2, 3
• Joint examination: Document specific joints with swelling versus tenderness only, range of motion, and presence of morning stiffness duration 6, 5
• Pharyngeal examination: Already noted swollen non-erythematous tonsils, but assess for exudates or other infectious signs 5

Most Likely Diagnosis: Subacute Thyroiditis

The clinical presentation strongly suggests subacute thyroiditis masquerading as fever of unknown origin, particularly given the temporal relationship to her previous hyperthyroidism treatment and the constellation of fever, joint pain, and throat symptoms. 1, 2, 3

Supporting Evidence

• Fever pattern: Subacute thyroiditis commonly presents with prolonged fever (37.8-37.9°C matches typical low-grade to moderate fever) 3
• Joint involvement: Migratory polyarthralgias are well-documented in subacute thyroiditis 2
• Post-viral timing: Typically occurs 2-8 weeks after upper respiratory infection; her pneumonia history with persistent productive cough suggests ongoing or recent respiratory pathology 1, 2
• Throat symptoms: Swollen tonsils and anterior neck involvement are characteristic 2, 3

Treatment Algorithm

If Subacute Thyroiditis Confirmed (TSH suppressed, elevated free T4, elevated ESR/CRP)

Initiate high-dose NSAIDs as first-line therapy for mild to moderate cases, with corticosteroids reserved for severe or refractory cases. 2

Mild to Moderate Disease

• Naproxen 500 mg twice daily (patient tolerates paracetamol, so likely tolerates NSAIDs) 6, 2
• Alternative: Aspirin 650 mg every 4-6 hours if naproxen not tolerated 2
• Symptomatic management: Continue paracetamol 500 mg as needed for fever (maximum 4000 mg/24 hours) 7

Severe or Refractory Disease (if no improvement after 48-72 hours)

• Prednisone 40 mg daily for 1-2 weeks, then taper over 4-6 weeks 2
• Monitor: Thyroid function every 4-6 weeks as patients typically transition through hyperthyroid → euthyroid → hypothyroid phases 2

If Inflammatory Arthritis Confirmed (elevated RF/anti-CCP, synovitis on examination)

Initiate acetaminophen and NSAIDs for Grade 1 symptoms, escalating to prednisone 10-20 mg daily for Grade 2 symptoms if inadequately controlled. 6, 5

• Grade 1 (current presentation): Paracetamol 500-1000 mg every 6 hours plus naproxen 500 mg twice daily 6, 5
• If inadequate response after 4-6 weeks: Prednisone 10-20 mg daily with slow taper 6, 5
• Rheumatology referral: If symptoms persist beyond 4 weeks or if synovitis develops 6, 5

Critical Management Considerations

Acid Reflux Management

• Continue omeprazole but monitor closely if NSAIDs initiated, as combination increases GI bleeding risk 6
• Consider: Increasing omeprazole to 40 mg daily if NSAIDs required 6

Methimazole History

• Important caveat: Antithyroid arthritis syndrome (AAS) from methimazole can present with fever, rash, myalgia, and migratory polyarthralgia, though typically occurs during active treatment 8
• Timeline argues against AAS: Patient was "declared cleared" from hyperthyroidism, suggesting methimazole discontinued months ago 8

Persistent Productive Cough

• Chest X-ray indicated: Green-gray and yellow sputum since pneumonia suggests possible chronic bronchitis or incomplete resolution 6
• Consider: Sputum culture if cough worsens or fever persists despite treatment 6

Monitoring Schedule

• Week 1: Reassess symptoms, repeat inflammatory markers if subacute thyroiditis suspected 2
• Week 4-6: Repeat thyroid function tests and inflammatory markers 6, 4, 5, 2
• Ongoing: Serial rheumatologic examinations every 4-6 weeks if inflammatory arthritis confirmed 6, 5

Red Flags Requiring Immediate Escalation

• Severe anterior neck pain with dysphagia: May indicate suppurative thyroiditis requiring antibiotics 2
• Persistent fever >39°C: Suggests alternative infectious etiology 3
• Development of true muscle weakness (not just pain): Consider inflammatory myositis requiring higher-dose corticosteroids 6
• Joint swelling with synovitis: Requires rheumatology consultation within 1-2 weeks 6, 5