Session Information
Session Type: ACR Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose: Radiological studies to distinguish between dermatomyositis (DM) and polymyositis (PM) are few. We predicted that the magnetic resonance imaging (MRI) findings of skeletal muscle would differ between DM and PM because of the differences in the histopathological findings associated with the disorders. Our objective was to establish distinctive MRI characteristics of skeletal muscle in patients with DM or PM.
Methods: The MRI findings (short-tau inversion recovery [STIR] and gadolinium-enhanced fat-suppressed T1-weighted imaging [Gd-T1WI]) of proximal limb skeletal muscles in patients with DM (n = 53) or PM (n = 32) were evaluated. Differences in the percentage appearances of the following findings in the axial plane between DM and PM patients and between autoantibody-positive and autoantibody-negative PM patients were analyzed: structures with high signal intensity (HSI) (subcutaneous adipose tissue, fascia, muscle); distributions of HSI areas in muscle (diffuse, patchy, peripheral); patterns of HSI in muscle (honeycomb, foggy, strong high signal intensity [SHSI] ).
Results: Among the 79 patients with abnormal MRI findings, 48 were diagnosed with DM and 31 were diagnosed with PM. Of these, Gd-T1WI was performed in 45 patients with DM and 27 patients with PM. Table 1 shows the differences in the percentage appearances of MRI findings between DM and PM patients. On STIR and Gd-T1WI images, the percentage appearances of the following characteristics were higher in DM patients than in PM patients: subcutaneous HSI, fascial HSI, peripheral distribution in muscle, honeycomb pattern in muscle. Patchy distribution and foggy pattern in muscle were higher in PM patients than in DM patients. There were no significant differences between the groups for diffuse distribution and SHSI pattern in muscle. Table 2 shows the differences in the percentage appearances of MRI findings between the autoantibody-positive and autoantibody-negative PM groups. The percentage appearances of subcutaneous and fascial HSI on STIR and Gd-T1WI images were higher in autoantibody-positive PM patients than in autoantibody-negative PM patients. Patchy distribution in muscle on Gd-T1WI was higher in autoantibody-negative PM patients than in autoantibody-positive PM patients.
Conclusion: Subcutaneous and fascial HSI, peripheral distribution in muscle, and honeycomb pattern in muscle are characteristic MRI findings in patients with DM, whereas patchy distribution and foggy pattern in muscle are characteristic MRI findings in patients with PM. MRI could be a useful tool for diagnosing DM and PM.
| Table 1: Percentage appearances of characteristic findings on MRI in patients with DM or PM* | |||
| STIR | DM ( n = 48 ) | PM ( n = 31 ) | p-value† |
| subcutaneous HSI | 34 (70.8) | 9 (29.0) | <0.001 |
| fascial HSI | 41 (85.4) | 13 (41.9) | <0.001 |
| peripheral distribution | 43 (89.6) | 14 (45.2) | <0.001 |
| diffuse distribution | 23 (47.9) | 14 (45.2) | 0.81 |
| patchy distribution | 12 (22.9) | 15 (48.4) | <0.05 |
| honeycomb pattern | 34 (70.8) | 11 (35.5) | <0.01 |
| foggy pattern | 3 (6.3) | 17 (54.8) | <0.001 |
| SHSI pattern | 9 (18.8) | 2 (6.5) | 0.12 |
| Gd-T1WI | DM ( n = 45 ) | PM ( n = 27 ) | p-value† |
| subcutaneous HSI | 31 (68.9) | 8 (29.6) | <0.01 |
| fascial HSI | 37 (82.2) | 10 (37.0) | <0.001 |
| peripheral distribution | 40 (88.9) | 12 (44.4) | <0.001 |
| diffuse distribution | 20 (44.4) | 9 (33.3) | 0.35 |
| patchy distribution | 10 (22.2) | 16 (59.3) | <0.01 |
| honeycomb pattern | 34 (75.6) | 7 (25.9) | <0.001 |
| foggy pattern | 3 (6.7) | 13 (48.1) | <0.001 |
| SHSI pattern | 6 (13.3) | 2 (7.4) | 0.44 |
|
* Values are the number (%). † Statistical analysis was performed by Pearson’s chi-square test. |
|||
| Table 2: Percentage appearances of characteristic findings on MRI in autoantibody-positive and autoantibody-negative PM groups* | |||
| STIR | AA (+) ( n = 18 ) | AA (-) ( n = 13 ) | p-value† |
| subcutaneous HSI | 8 (44.4) | 1 (7.7) | <0.05 |
| fascial HSI | 13 (72.2) | 0 (0.0) | <0.001 |
| peripheral distribution | 8 (44.4) | 5 (38.5) | 1.00 |
| diffuse distribution | 8 (44.4) | 6 (46.2) | 1.00 |
| patchy distribution | 6 (33.3) | 9 (69.2) | 0.073 |
| honeycomb pattern | 9 (50.0) | 2 (15.4) | 0.066 |
| foggy pattern | 7 (38.9) | 10 (76.9) | 0.067 |
| SHSI pattern | 1 (5.6) | 1 (7.7) | 1.00 |
| Gd-T1WI | AA (+) ( n = 15 ) | AA (-) ( n = 12 ) | p-value† |
| subcutaneous HSI | 7 (46.7) | 1 (8.3) | <0.05 |
| fascial HSI | 10 (66.7) | 0 (0.0) | <0.001 |
| peripheral distribution | 7 (46.7) | 5 (41.7) | 1.00 |
| diffuse distribution | 6 (40.0) | 3 (25.0) | 0.68 |
| patchy distribution | 6 (40.0) | 10 (83.3) | <0.05 |
| honeycomb pattern | 6 (40.0) | 1 (8.3) | 0.091 |
| foggy pattern | 5 (33.3) | 8 (66.7) | 0.13 |
| SHSI pattern | 1 (6.7) | 1 (8.3) | 1.00 |
|
* Values are the number (%). AA (+) = an autoantibody-positive PM group, containing patients with myositis-specific autoantibodies, myositis-associated autoantibodies, and/or other connective tissue disease-specific autoantibodies; AA (-) = an autoantibody-negative PM group, containing patients without these autoantibodies. † Statistical analysis was performed by Fisher’s exact test. |
|||
To cite this abstract in AMA style:
Ukichi T, Yoshida K, Matsushima S, Kawakami G, Noda K, Furuya K, Kurosaka D. Magnetic Resonance Imaging of Skeletal Muscles in Patients with Dermatomyositis and Polymyositis: Novel and Distinctive Characteristic Findings [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/magnetic-resonance-imaging-of-skeletal-muscles-in-patients-with-dermatomyositis-and-polymyositis-novel-and-distinctive-characteristic-findings/. Accessed .« Back to 2017 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/magnetic-resonance-imaging-of-skeletal-muscles-in-patients-with-dermatomyositis-and-polymyositis-novel-and-distinctive-characteristic-findings/