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TOPLINE:

Commercial autoantibody testing showed no significant differences in the prevalence of myositis-specific and myositis-associated autoantibodies between patients with classic dermatomyositis and those with clinically amyopathic dermatomyositis. However, antinuclear antibodies were more common in patients with classic dermatomyositis than in those with the clinically amyopathic form.

METHODOLOGY:

• Researchers conducted a cross-sectional study to compare the positivity rates of commonly tested myositis-specific autoantibodies, myositis-associated autoantibodies, and antinuclear antibodies between patients with classic dermatomyositis and those with clinically amyopathic dermatomyositis.
• They identified 320 adult patients with dermatomyositis (mean age, 53 years; 86% women) who had undergone myositis autoantibody testing between 2016 and 2024; of these, 62% had classic dermatomyositis with clinically evident muscle disease, and 38% had clinically amyopathic dermatomyositis without muscle involvement.
• Autoantibody testing was performed using 16 panel types across five commercial laboratories, with each patient undergoing a mean of 1.2 panels.

TAKEAWAY:

• The positivity rates for myositis-specific autoantibodies showed no significant difference between patients with classic dermatomyositis (47%) and those with clinically amyopathic dermatomyositis (40%; P = .20); anti-transcription intermediary factor-1 gamma emerged as the most common myositis-specific autoantibody in the two subtypes.
• Similarly, the positivity rate for myositis-associated antibodies was comparable between patients with classic dermatomyositis (29%) and those with the clinically amyopathic form (26%; P = .65); anti-Sjögren syndrome-related antigen A was the most prevalent myositis-associated antibody in both subtypes.
• Antinuclear antibody positivity was significantly higher in patients with classic dermatomyositis vs clinically amyopathic dermatomyositis (63% vs 49%; P = .045), suggesting a potential association between antinuclear antibody positivity and muscle involvement.
• Furthermore, antinuclear antibody positivity was noted in more than one third of patients with negative results for myositis-specific and myositis-associated autoantibodies.

IN PRACTICE:

“Although DM [dermatomyositis] autoantibody profile may be a helpful tool in prognosis when positive, its utility is limited by the variability in detection methods and tested antibodies,” the authors wrote.

SOURCE:

The study was led by Xiwei Yang, Department of Dermatology, University of Pennsylvania Perelman School of Medicine, Philadelphia. It was published online on September 10, 2025, in JAMA Dermatology.

LIMITATIONS:

There may have been variations in the detection methods and tested antibodies used across different commercial panels.

DISCLOSURES:

This study was funded by grants from the US National Institutes of Health and the US Department of Veterans Affairs. One author reported receiving personal fees and grants from, serving on medical advisory boards of, and having other ties with various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.