Work

Taming the tiger: insights into sarcoid myositis through 18F-FDG PET/MRI imaging

Year: 2024

Type: article

Abstract: Myositis, characterized by inflammation of the skeletal muscles, represents a significant manifestation of sarcoidosis, a systemic granulomatous disease. While sarcoidosis traditionally affects the lungs and lymph nodes, its involvement of the musculoskeletal system, termed sarcoid myositis, presents unique diagnostic and therapeutic challenges.1 In this context, MRI and 18F-fluorodeoxyglucose (18F-FDG) PET play a pivotal role in unraveling the complexities of sarcoidosis myositis, assessing the extent and severity of the disease, its progression, and treatment response.2,3 To enhance diagnostic accuracy, the integration of anatomical and functional imaging is often achieved through “hybrid” modalities such as PET/CT and, more recently but less clinically available, PET/MRI. Herein, we present the case of an adult patient with cough, myalgia and recent history of uveitis and epididimitis, addressed for further investigation of multiple enlarged mediastinal lymph nodes and increased serum angiotensin-converting-enzyme. Sarcoidosis was suspected and patient underwent 18F-FDG PET/MRI whole-body imaging revealing intense radiotracer uptake in thoracic nodes without visceral involvement, particularly heart. However, intense 18F-FDG uptake with a characteristic “striped” or “tiger-like” pattern4 was observed in upper and lower leg muscles corresponding to both high signal intensity on water-sensitive T2-weighted MRI, and restricted water diffusion on diffusion-weighted MRI (DWI-MRI) (Figure 1a). These findings reflected the muscle edema related to inflammatory involvement of skeletal muscles. The diagnosis of sarcoid myositis was confirmed by muscular biopsy and patient started treatment with prednisone (30 mg/day degressive for 4 months) and methotrexate (25 mg/week for three months, then 20 mg/week for one month). Patient's symptoms greatly improved and follow-up 18F-FDG PET/MRI, performed after four months of treatment, showed complete resolution of both 18F-FDG uptake abnormalities and MRI signs of muscular edema (Figure 1b). Accordingly, the treatment was modified by progressively tapering the doses of prednisone and methotrexate. 18F-FDG PET/MRI results in a patient with sarcoid myositis at diagnosis (a) and after four months of treatment with prednisone and methotrexate (b). Prednisone and methotrexate are effective in managing muscular sarcoidosis. Prednisone is often used as a first-line treatment to provide rapid relief of symptoms, while methotrexate may be added to the treatment regimen for long-term management or to reduce the dose of prednisone needed, thus minimizing potential side effects associated with prolonged corticosteroid use. Regular monitoring and follow-up are essential to ensure the effectiveness of treatment and to manage any potential side effects or complications. By providing both functional and anatomical information within a single imaging modality, 18F-FDG PET/MRI offers a comprehensive approach for evaluating sarcoid myositis, facilitating early diagnosis and tailored therapeutic interventions. One of the key advantages of 18F-FDG PET/MRI imaging is its ability to provide whole-body assessment, allowing for the detection of multifocal muscle involvement and concurrent extramuscular manifestations of sarcoidosis. Ultimately, we advocate for the use of 18F-FDG PET/MRI in assessing sarcoid myositis, providing insights into disease activity, the extent of muscle involvement, and treatment response. As research in this field continues to evolve, 18F-FDG PET/MRI is poised to remain a cornerstone in the management of sarcoidosis-related myositis, contributing to improved patient care and outcomes. Ashjan Kaseb (Data curation [equal], Formal analysis [equal], Writing—original draft [equal]), Margherita Giannini (Data curation [equal], Investigation [equal]), Boubacar Dramé (Data curation [equal], Formal analysis [equal]), Thibault Willaume (Data curation [equal], Formal analysis [equal], Investigation [equal]), Alain Meyer (Formal analysis [equal], Funding acquisition [equal], Investigation [equal]), and Alessio Imperiale (Conceptualization [equal], Data curation [equal], Formal analysis [equal], Investigation [equal], Supervision [equal], Validation [equal], Writing—original draft [equal], Writing—review & editing [equal]) None declared.

Source: QJM

DOI: 10.1093/qjmed/hcae075

Authors: A Kaseb, M Giannini, B Dramé, T Willaume, A Meyer, A Imperiale