Myositis autoantibodies, particularly anti-p155/140, are associated with a chronic disease course in those with juvenile idiopathic inflammatory myopathies (JIIM), according to data published in the journal Arthritis & Rheumatology.
Several factors present at the time of diagnosis of JIIM have been associated with a chronic course, although research on the magnitude of these associations is limited. The current study sought to identify a number of early factors associated with disease course in patients with JIIM.
The study included 365 participants from a large JIIM registry. Researchers performed univariable and multivariable multinomial logistic regression analyses, which included demographic characteristics, early clinical features, serum muscle enzyme levels, myositis autoantibody levels, environmental exposures, and presence of immunogenic polymorphisms.
Multivariate analysis revealed that the presence of myositis-specific autoantibodies was independently associated with a chronic or polycyclic disease course. The presence of any myositis-associated autoantibodies (multinomial odds ratio [OR]: 4.8; 95% confidence interval [CI]: 1.8-12.9 and 3.5; 95% CI: 1.1-11.1) and documented infection within 6 months of illness onset (multinomial OR: 2.5; 95% CI: 1.0-5.8 and 4.7; 95% CI: 1.9-11.9) were associated with a polycyclic disease course.
Higher overall clinical symptom score was associated with chronic disease course compared with polycyclic course (multinomial OR: 146; 95% CI: 8-2526 per 0.01 unit increase in score).
Severe illness at disease onset was associated with a chronic course compared with a monocyclic course (multinomial OR: 2.1; 95%CI: 1.2-3.8 and 2.6; 95% CI: 1.4-4.9), and the presence of anti-p155/140 autoantibodies was associated with a chronic or polycyclic course compared with a monocyclic course (multinomial OR: 3.9; 95% CI: 2.0-7.7 and 2.3; 95% CI: 1.1-5.0).
Photosensitivity (OR: 2.9; 95% CI: 1.5-5.8), V-sign or shawl sign rashes (OR: 2.2; 95% CI: 1.0-4.9), and cuticular overgrowth (OR: 3.2; 95% CI: 1.4-7.5) were found on univariable analysis to be associated with a chronic course compared with a monocyclic course. The mean ultraviolet index and highest ultraviolet index in the month before diagnosis were associated with a chronic disease course in boys (OR: 1.5; 95% CI: 1.1-2.1 and 1.3; 95% CI 1.1-1.7).
“These findings suggest that early factors, which are associated with poorer outcomes in JIIM, can be identified,” the authors noted. “Future studies are needed to confirm these associated factors and to identify their value in prognosis.”
Summary and Clinical Applicability
Previous studies have identified several factors that characterize a chronic disease course in JIIM, including tumor necrosis 308A allele, extensive myopathic and severe arteropathic changes in muscle tissue, longer duration of untreated disease, and higher baseline skin activity. The current study found that myositis-specific autoantibodies, specifically anti-p155/140, and several clinical features and environmental exposures found at the time of diagnosis were also associated with chronic disease course in JIIM.
These findings were limited by several aspects of the study design, including measurement of myositis autoantibodies at the time of study enrollment (at a median of 2.1 years after diagnosis) instead of at the time of initial diagnosis.
The results of the study suggest that early factors associated with poor outcomes in JIIM can be identified at illness onset. The authors suggest further research should be conducted to confirm the factors associated with chronic disease course and to determine their clinical value in prognosis. Because treatment regimens were not available for this study, future studies should also explore whether treatment has any effect on disease course and levels of autoantibody titers.
Habers GE, Huber AM, Mamyrova G, et al. Association of myositis autoantibodies, clinical features, and environmental exposures at illness onset with disease course in juvenile myositis. Arthritis Rheumatol. 2016;68(3):761-768. doi: 10.1002/art.39466.