Subcutaneous Infection With Snow Leopard Sign on 18F-FDG PET/CT Mimicking Subcutaneous Panniculitis-Like T-Cell Lymphoma

A 37-year-old man presented with a 2-month history of fever of unknown origin and erythema rashes on the trunk and limbs. 18F-FDG PET/CT revealed increased 18F-FDG uptake in subcutaneous panniculitis, forming a snow leopard sign, along with enlarged lymph nodes, which suggested subcutaneous panniculitis-like T-cell lymphoma. However, skin biopsy indicated subcutaneous infection, and bone marrow biopsy revealed no abnormal lymphocytes. After anti-infection treatment, symptoms improved, leading to a final diagnosis of systemic infection. This case demonstrates how extensive subcutaneous infections on PET/CT could be misinterpreted as subcutaneous panniculitis-like T-cell lymphoma.