Here, we present the first 18F-FDG PET images for the initial evaluation and treatment monitoring of TEMPI in a 51-year-old woman, who exhibited polycythemia (EPO:5,448 mIU/ml) without JAK2 mutation, telangiectasias, monoclonal IgG lambda gammopathy (13.9) g/L and 7% dysmorphic plasma cells (CD38 + CD138+), occasionally clustered, in favor of tumoral plasmacytomas. The gene discussed is SDC1; the disease is polycythemia.