18F-FDG PET/CT in patients with polymyositis/dermatomyositis: correlation with serum muscle enzymes

Abstract

Background Muscle enzymes are the major noninvasive diagnostic parameters useful in polymyositis/dermatomyositis (PM/DM). Few studies have yet correlated findings on 18 F-FDG PET with disease activity in patients with PM/DM. Purpose We evaluated 18 F-FDG muscle uptake in patients with PM/DM compared with non-muscular diseases and correlated the results with serum muscle enzymes. Methods A total of 28 patients with untreated PM/DM and 28 control patients with non-muscular diseases were examined with 18 F-FDG PET/CT. 18 F-FDG uptake was evaluated in 9 proximal skeletal muscle regions bilaterally. The uptake was scored as follows: 0 = less than that of the mediastinal blood vessels, 1 = greater than or equal to that of the mediastinal blood vessels, and 2 = greater than or equal to that of the liver. A score 1 or 2 was considered positive. The mean and maximum standardized uptake values (SUV) were calculated in each muscle and were averaged for all muscle regions. PET findings were correlated with serum muscle enzymes. Results 18 F-FDG uptake was observed in 82% of patients with PM/DM and 7% of control patients. The number of positive regions, total score, mean SUVmean, and mean SUVmax in patients with PM/DM were significantly higher than those in the control patients (all P < 0.001). The total score of 2 was the best cut-off value that could discriminate patients with PM/DM from control patients. The total score, mean SUVmean, and mean SUVmax showed significant correlations with creatine kinase ( P = 0.047, 0.002, 0.010, respectively) and aldolase ( P = 0.036, 0.005, 0.038, respectively). Conclusion 18 F-FDG PET/CT using visual and SUV methods demonstrated its usefulness by discriminating PM/DM from non-muscular diseases and correlating with serum muscle enzymes in patients with PM/DM.

F-18-FDG PET/CT findings of paraneoplastic dermatoses

“…While lung and gastrointestinal neoplasms are the mostly reported in DM patients, different malignancies including nasopharynx, ovarian, breast, prostate, kidney cancers, and different types of hematological malignancies are also reported. In Japan, gastric cancer is found in up to 25% of patients [ 37 ]. The etiopathogenesis of DM is still unclear, but recent studies have suggested that DM might arise as an autoimmune response against cancer which cross-reacts with regenerating muscle cells, as myositis-specific autoantigens are expressed in both tumor cells and undifferentiated myoblasts [ 34 – 42 ].…”

“…The etiopathogenesis of DM is still unclear, but recent studies have suggested that DM might arise as an autoimmune response against cancer which cross-reacts with regenerating muscle cells, as myositis-specific autoantigens are expressed in both tumor cells and undifferentiated myoblasts [ 34 – 42 ]. An association between autoantibody (anti-155/140 or transcriptional intermediary factor 1) IgG and paraneoplastic DM also has been described [ 35 , 37 ].…”

“…Whole-body FDGPET/CT often shows symmetrical muscle hyper-metabolism representing the inflammatory nature of DM, with correlation with serum muscle enzymes in DM patients [ 37 ]. Proximal muscles of shoulders, buttocks and thigh are the most frequent FDG-positive regions.…”

The Role of Quantitative and Semi-quantitative [18F]FDG-PET/CT Indices for Evaluating Disease Activity and Management of Patients With Dermatomyositis and Polymyositis

“…The database search identified 252 records found and 236 records were excluded after title/abstract screening and full-text content because those did not provide any relevant information on the topic of this review (Figure 1). Sixteen articles were eligible for a more detailed description in this review (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31).…”

“…Two studies compared [ 18 F]FDG muscle uptake to mediastinal bloodpool activity with an uptake equal or higher than mediastinal blood pool being considered positive (20,28). Tateyama et al (20) used a 2-point grading scale (0 = uptake < mediastinal blood pool and 1 = ≥ mediastinal blood pool) which was evaluated in 16 regions resulting in a composite score ranging from 0 to 16.…”