To investigate the source of fever in a patient with bilateral epididymo-orchitis and negative cultures.
Approach:
Clinical Presentation: A 56-year-old man presented with bilateral epididymo-orchitis, high fever, headache, and lower-limb myalgia despite antibiotic treatment.
Diagnostic Imaging: Whole-body ^18F-FDG PET/CT was performed, revealing bilateral irregular uptake suggestive of polyarteritis nodosa.
Treatment: Intermediate-dose prednisone was administered, followed by azathioprine as a steroid-sparing agent, leading to clinical improvement.
Biopsy: A quadriceps biopsy was conducted targeting a PET-positive area but showed no vasculitis.
Key Findings:
Negative results for multiple infectious and autoimmune tests.
The PET/CT pattern described as 'ant-farm-like' supports the diagnosis of polyarteritis nodosa, as noted by Yamamoto et al.
Clinical and biochemical response was achieved two weeks after initiating treatment.
Interpretation:
The 'ant-farm-like' pattern on PET may indicate a specific phenotype of polyarteritis nodosa characterized by high inflammatory burden, as proposed in the literature.
Limitations:
The specificity of the 'ant-farm-like' PET finding remains under evaluation.
The biopsy was performed after corticosteroid initiation, potentially affecting results.
Conclusion:
The case illustrates the utility of FDG-PET/CT in diagnosing polyarteritis nodosa in a patient with fever of unknown origin.
The approval was based on reduced proteinuria, and an ongoing trial is required to determine whether atacicept slows long-term kidney function decline.
