Active Shingles Infection as Detected on (18)F-FDG PET/CT

Area of Science:

• Nuclear Medicine
• Oncology
• Dermatology

Background:

• Follicular lymphoma patients undergoing chemotherapy may present with various complications.
• Varicella zoster infection can manifest with cutaneous and sometimes systemic symptoms.
• 18F-FDG PET-CT is a crucial imaging modality for lymphoma staging and monitoring treatment response.

Purpose of the Study:

• To report a case of increased metabolic activity on 18F-FDG PET-CT secondary to Varicella zoster infection in a lymphoma patient.
• To emphasize the importance of distinguishing post-herpetic 18F-FDG uptake from malignant metastasis.
• To highlight the transient nature of this imaging finding.

Main Methods:

• A 56-year-old male with recurrent follicular lymphoma was evaluated with serial 18F-FDG PET-CT scans.
• The patient developed a rash diagnosed as Varicella zoster infection.
• Imaging findings were correlated with clinical presentation and follow-up scans.

Main Results:

• Initial 18F-FDG PET-CT demonstrated a dermatomal band of increased metabolic activity in the upper back, corresponding to the site of Varicella zoster eruption.
• This abnormal uptake resolved on subsequent 18F-FDG PET-CT scans performed 4 months later.
• The finding was successfully differentiated from tumor recurrence or metastasis.

Conclusions:

• Varicella zoster infection can cause focal, transient 18F-FDG uptake on PET-CT scans.
• Radiologists and clinicians must consider post-infectious inflammatory changes to avoid misinterpreting them as malignancy in patients with a history of cancer.
• Awareness of this imaging pitfall is crucial for accurate patient management.