F¹⁸-FDG PET-CT Findings in Juvenile-Onset Polyarteritis Nodosa: A First Series and Literature Review

Objectives: To investigate the findings associated with juvenile polyarteritis nodosa (PAN) on F18-FluoroDeoxyglucose (FDG), positron emission tomography combined with computed tomography (PET-CT). Methods: Patients diagnosed with juvenile PAN (onset <18 years) who underwent a PET-CT at diagnosis (before therapy) were enrolled. PET-CT images were systematically analyzed to identify abnormal findings associated with PAN. In addition, a systematic literature review was performed to identify previously published cases. Results: Six patients with biopsy-confirmed PAN were identified (age at onset 10-17 years). PET-CT was abnormal in all patients. Patchy muscular and subcutaneous FDG uptake with a symmetric distribution in the lower limbs was present in 4/6 patients. Increased FDG uptake in large arteries was found in 1/6 patients. FDG-avid bone lesions were identified in 2/6; additional MRI and bone biopsy results were consistent with chronic non-infectious osteomyelitis (CNO). Unspecific inflammatory findings (medullar and lymphoid organs hypermetabolism) were present in 6/6; these were the only abnormalities present in 2/6 patients. We found this pattern of PET-CT muscular involvement to differ from juvenile dermatomyositis and septic emboli (n = 7 and 2 patients, respectively). In addition, we identified four previously published cases of juvenile PAN investigated with PET-CT: one with FDG-avid muscular and subcutaneous foci, one with increased uptake in large arteries, and two with nonspecific signs (lymphoid organs hypermetabolism). Conclusions: This is the first series of juvenile PAN investigated with PET-CT. Diffuse, patchy hypermetabolic foci in the muscular and subcutaneous tissue of the lower limbs were the most common findings. These features should lead to suspicion of PAN. Further research is needed to assess the diagnostic value of PET-CT in PAN.