A 66-year-old woman with locally advanced lung adenocarcinoma underwent FDG-PET/CT, which revealed superior vena cava invasion and thrombosis of the brachiocephalic veins. Tracer injection on the side of thrombosis demonstrated hypermetabolism in the dorsal spine, likely due to collateral venous drainage. Following chemoradiotherapy and early discontinuation of immunotherapy for toxicity, she developed cervicobrachial neuralgia 18 months later. MRI showed marrow replacement lesions and FDG-PET/CT identified bone recurrence at D1, correlating with previously nonspecific fixation abnormalities. This case raises the question of whether vertebral venous stasis may favor metastatic grafting and highlights the potential need for contralateral FDG injection.

A 50-year-old woman presented a dry syndrome, joint pain, inflammatory syndrome, polyclonal hypergammaglobulinemia, and tubulointerstitial nephritis. Imaging studies (including FDG PET/CT) revealed infrarenal retroperitoneal fibrosis with periaortitis and hypermetabolic osteosclerotic lesions. Bone scintigraphy demonstrated intense uptake in the femoral, tibial, and radial regions, suggestive of non-Langerhans histiocytosis, specifically Erdheim-Chester disease. A bone biopsy confirmed the presence of IgG4-positive plasma cells but no histiocytes. The patient received corticosteroid therapy followed by rituximab, resulting in a complete response. This case suggests an atypical manifestation of bone lesions in IgG4-related disease, emphasizing the diagnostic challenge between IgG4-related disease and Erdheim-Chester disease.

ABSTRACT VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is an adult-onset autoinflammatory disease caused by somatic UBA1 mutations first described in 2020. Most of these patients met clinical criteria for an inflammatory syndrome (relapsing polychondritis, Sweet syndrome, polyarteritis nodosa, or giant-cell arteritis) or a hematologic condition (myelodysplastic syndrome or multiple myeloma) or both. We described here an FDG PET/CT "leopard man" appearance, with abnormal marrow recruitment the findings, in a 70-year-old man diagnosed with a VEXAS syndrome.

Objective F-18-fluorodeoxyglucose PET/CT (FDG-PET/CT) is widely used in patients with large vessel vasculitis. The benefits of FDG-PET/CT in PAN has only ever been assessed in three case reports. Our aim was to describe FDG-PET/CT findings in 10 patients with newly diagnosed PAN. Methods This was a retrospective study of patients with PAN who underwent FDG-PET/CT at diagnosis between 2017 and 2020. The FDG-PET/CT data were analysed retrospectively. Results Ten patients were included: nine men and one woman with a median age of 67 years (range 43-78). PAN was diagnosed according to ACR criteria in nine patients and histologically in one. All patients had high CRP levels (median 223 mg/l). The main FDG-PET/CT abnormality was increased tracer uptake in the muscles, particularly in the connective tissue (perimysium, epimysium) (n = 7), and in linear (n = 5) or focal (n = 2) patterns. Increased FDG uptake in large-diameter vessels was observed in four patients, in the humeral (n = 4), femoral (n = 1) and common interosseous arteries (n = 1). Nine patients had bone marrow FDG uptake and six had splenic FDG uptake. Three had synovitis and three had lymph node uptake. One patient had subcutaneous FDG uptake with a 'leopard skin' appearance. Conclusions FDG-PET/CT seems to be a useful non-invasive imaging technique for diagnosing PAN, particularly in patients with non-specific systemic features. Tracer uptake in muscular connective tissue seems to be a recurrent sign in patients with PAN and may be pathognomonic.