In a 60‑year‑old woman presenting with diffuse musculoskeletal pain, markedly elevated erythrocyte sedimentation rate, chronic anemia, leukocytosis, and a urinary tract infection (UTI) with normal cardiac troponin, what is the most likely diagnosis and how should it be initially managed?

Giant Cell Arteritis (Temporal Arteritis) with Concurrent UTI

In this 60-year-old woman with diffuse pain, markedly elevated ESR (85 mm/hr), chronic anemia, and leukocytosis in the setting of UTI, giant cell arteritis (GCA) is the most likely diagnosis requiring urgent evaluation and treatment, while the UTI should be treated concurrently but does not explain the constellation of findings. 1

Diagnostic Reasoning

Why GCA is the Primary Diagnosis

• ESR of 85 mm/hr has high diagnostic value for GCA: An ESR >80 mm/hr yields a positive likelihood ratio of 2.79 and specificity of 81.8% for GCA in patients over 50 years old with appropriate symptoms 1
• Diffuse musculoskeletal pain in a 60-year-old woman with markedly elevated inflammatory markers is classic for GCA-associated polymyalgia rheumatica (PMR): PMR occurs in approximately 40-60% of GCA patients and presents with bilateral shoulder and hip girdle pain and stiffness 1
• Chronic anemia is expected in GCA: Anemia occurs commonly in GCA as part of the systemic inflammatory response, is normochromic and normocytic, and resolves with resolution of inflammation 1

Why the UTI Does Not Explain the Clinical Picture

• Leukocytosis from UTI alone does not produce ESR elevation of this magnitude: While febrile UTI can cause leukocytosis (seen in 90.2% of cases), the ESR elevation is typically modest, and the combination of ESR 85 mm/hr with chronic anemia points to a chronic inflammatory process rather than acute infection 2
• The presence of chronic anemia indicates a process predating the acute UTI: Anemia of chronic disease develops over weeks to months in conditions like GCA, autoimmune diseases, and chronic infections, not from an acute UTI 3

Immediate Diagnostic Workup

Essential Tests to Perform Urgently

• Temporal artery examination: Palpate for thickening, tenderness, or loss of pulse—temporal artery abnormalities have a positive likelihood ratio of 3.14 and specificity of 83.6% for GCA 1
• Ophthalmologic evaluation within 24 hours: Anterior ischemic optic neuropathy occurs in 23.9% of GCA cases and represents a medical emergency; visual loss can be permanent if treatment is delayed 1
• C-reactive protein (CRP) measurement: CRP elevation has a positive likelihood ratio of 1.73 and sensitivity of 79.2% for GCA; it complements ESR and normalizes more quickly with treatment 1
• Complete blood count with differential: Document the degree of anemia and confirm neutrophilic leukocytosis pattern 1

Tests to Exclude Alternative Diagnoses

• Creatine kinase (CK) level: Normal CK with diffuse pain strongly argues against inflammatory myositis, as muscle weakness (not pain) is the hallmark of myositis, and CK is elevated in most myositis cases 4, 1
• Rheumatoid factor and anti-CCP antibodies: To exclude elderly-onset rheumatoid arthritis, though the absence of joint swelling makes this unlikely 1
• Serum ferritin: Very high ferritin levels (>4000 ng/mL) would suggest Adult-Onset Still's Disease, though the age and clinical presentation make this less likely 1

Immediate Management Algorithm

Step 1: Initiate Corticosteroids Urgently (Do Not Wait for Biopsy)

• Start prednisone 40-60 mg daily (or 0.7-1 mg/kg/day) immediately if GCA is suspected based on clinical features and ESR >50 mm/hr: Delaying treatment to await temporal artery biopsy risks irreversible vision loss 1
• If visual symptoms are present or imminent, give intravenous methylprednisolone 500-1000 mg daily for 3 days before transitioning to oral prednisone: This provides more rapid and complete suppression of inflammation 1

Step 2: Arrange Temporal Artery Biopsy Within 1-2 Weeks

• Temporal artery biopsy remains the gold standard for diagnosis: Characteristic findings include granulomatous inflammation with giant cells, though skip lesions occur in 28% of cases 1
• Biopsy can be performed up to 2 weeks after starting corticosteroids without significantly affecting diagnostic yield: Do not delay treatment to arrange biopsy 1

Step 3: Treat the Concurrent UTI

• Initiate trimethoprim-sulfamethoxazole (one double-strength tablet twice daily) or an alternative antibiotic based on local resistance patterns: The UTI requires treatment but is not the primary diagnosis 5
• Recheck leukocyte count after 48-72 hours of antibiotic therapy: If leukocytosis persists despite UTI treatment and clinical improvement, this supports GCA as the primary inflammatory process 2

Monitoring Treatment Response

Clinical and Laboratory Parameters

• Assess symptom improvement within 24-72 hours: Dramatic improvement in pain and stiffness with corticosteroids is characteristic of GCA/PMR and supports the diagnosis 1
• Recheck CRP at 1 week: CRP normalizes more quickly than ESR during resolution of inflammation and is more useful for monitoring treatment response after corticosteroid initiation 1
• Monitor hemoglobin over 4-6 weeks: Anemia should improve as inflammation resolves with adequate corticosteroid therapy 1

Corticosteroid Tapering Strategy

• Maintain initial prednisone dose for 2-4 weeks until complete symptom resolution and CRP normalization: Premature tapering risks disease relapse 1
• Taper by 10 mg every 2 weeks down to 20 mg, then by 2.5 mg every 2-4 weeks: Total treatment duration is typically 12-24 months 1
• If symptoms recur during taper, increase prednisone back to the last effective dose: Approximately 50% of patients experience relapse during tapering 1

Critical Pitfalls to Avoid

Do Not Misattribute Findings to the UTI Alone

• Leukocytosis with UTI does not explain ESR 85 mm/hr or chronic anemia: These findings indicate a chronic systemic inflammatory process requiring separate evaluation 2, 3
• Do not assume normal troponin excludes all serious pathology: While troponin elevation would suggest myocarditis (requiring different management), normal troponin does not rule out GCA 6, 1

Do Not Delay Treatment Pending Confirmatory Testing

• GCA is a medical emergency due to risk of irreversible blindness: Anterior ischemic optic neuropathy occurs in nearly 1 in 4 patients, and treatment delay increases this risk 1
• Starting corticosteroids before biopsy does not preclude diagnosis: Histologic changes persist for up to 2 weeks after treatment initiation 1

Do Not Confuse with Fibromyalgia or Polymyalgia-Like Syndrome

• Fibromyalgia does not cause elevated ESR or CRP: If inflammatory markers are elevated in a patient with diffuse pain, consider GCA/PMR, not fibromyalgia 7
• Obesity can elevate CRP modestly but does not explain ESR 85 mm/hr: This degree of ESR elevation indicates true inflammatory disease, not obesity-related inflammation 7