18F-FDG PET/CT in the follow-up of large-vessel vasculitis: A study of 37 consecutive patients

Objective 18F-FDG PET/CT has proved to be of potential value for early diagnosis of large-vessel vasculitis (LVV), which frequently involves the aorta. However, its role in the follow-up of these patients has not been well established. Our aim was to evaluate the contribution of 18F-FDG PET/CT in this clinical situation. Methods This study included 37 consecutive patients (28 women, 66.5 ± 9.9 years) with an initial 18F-FDG PET/CT positive for LVV and a mean ± standard deviation follow-up PET/CT of 7.5 ± 2.9 months after the initial scan. A semiquantitative analysis of aortic wall uptake was performed calculating the target-to-background ratio (TBR: aortic wall uptake divided by blood pool uptake). The initial and follow-up TBR as well as the clinical and laboratory outcome were compared. Results Overall, the mean TBR decreased from 1.7 ± 0.5 at the initial scan to 1.5 ± 0.3 at the time of follow-up (p = 0.0001). In the 21 patients who experienced clinical improvement following therapy the TBR also decreased from 1.8 ± 0.6 to 1.5 ± 0.3 (p = 0.0002). However, in the other 16 patients, in whom the treating physician considered that there was no clinical improvement following therapy, no statistically significant differences in TBR were found when data from the first and the follow-up PET/CT scans were compared (1.6 ± 0.3 versus 1.5 ± 0.3, p = 0.1416). Patients who experienced clinical improvement following therapy showed a nonstatistically significant higher TBR at the time of disease diagnosis (1.8 ± 0.6 versus 1.6 ± 0.3; p = 0.12). Conclusions The results obtained in the present study highlight the impact of 18F-FDG PET/CT on the management of patients with LVV.Professor Gonzalez-Gay´s research was supported by “Fondo de Investigación Sanitaria” (grant PI12/00060 and PI15/00525) from “Instituto de Salud Carlos III” (ISCIII, Health Ministry, Spain). His work is also partially supported by RETICS Programs RD12/0009 (RIER) from ISCIII (Spain) (RD16/0012/0009)

Erdheim-Chester disease due to a novel internal duplication of NRAS: response to targeted therapy with cobimetinib

Histiocytoses encompass a group of exceptionally rare disorders characterized by the abnormal infiltration of tissues by histocytes. Among these, Erdheim-Chester disease (ECD) stands out as a multisystem histiocytosis that typically affects bones and various other tissues. Historically, the treatment of ECD has been challenging. However, recent breakthroughs in our understanding, particularly the discovery of somatic mutations in the RAS-MAPK pathway, have opened new opportunities for targeted therapy in a significant subset of patients with ECD and other histiocytoses. In this report, we present the case of a patient with ECD harboring a previously unidentified microduplication in the NRAS gene in a small fraction of skin cells. This discovery played a pivotal role in tailoring an effective therapeutic approach involving kinase inhibitors downstream of NRAS. This case underscores the crucial role of deep sequencing of tissue samples in ECD, enabling the delivery of personalized targeted therapy to patients.Funding: This work was supported by National Institutes of Health/National Cancer Institute grant P30 CA008748, and National Cancer Institute grant R37CA259260 (E.L.D. and K.S.P.). This work was also supported by the Frame Family Fund (E.L.D.), the Joy Family West Foundation (E.L.D.), the Applebaum Foundation (E.L.D.), and the Erdheim-Chester Disease Global Alliance (E.L.D.). Acknowledgments: The grammar and style of this manuscript were checked with ChatGPT (GPT-3.5), available at https://chat.openai.com/, accessed on 8 September 2023