Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.


Ethnic but not Gender Differences in Disease Manifestations in Dermatomyositis Patients.

Tjarnlund1,  Anna, Rider2,  Lisa G., Miller2,  Frederick W., Werth3,  Victoria P., Pilkington4,  Clarissa A., de Visser5,  Marianne, Forslund1,  Elin

Karolinska Institutet, Stockholm, Sweden
University of California, Los Angeles, Los Angeles, CA
Department of Neurology, Catharina-ziekenhuis, Eindhoven, Netherlands
Brigham & Womens Hospital, Boston, MA
University of Alabama and VA Medical Center, Birmingham, AL
National Institute of Environmental Health Sciences, National Institutes of Health, Bethesda, MD
Perelman School of Medicine at the University of Pennsylvania and Philadelphia V.A. Medical Center, Philadelphia, PA
Department of Rheumatology, Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom
Department of Neurology, Academic Medical Centre, Amsterdam, Netherlands
Brigham and Women's Hospital and Harvard Medical School, Boston, MA
Department of Neurology, University of Kansas Medical Center, Kansas City, MO
Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
Department of Neurology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA

Background/Purpose:

Dermatomyositis (DM) is a subset of idiopathic inflammatory myopathies (IIM), which are heterogeneous rheumatic disorders characterized by inflammation of skeletal muscle and progressive weakness. New and improved treatment is needed but a significant and fundamental problem for conducting clinical trials is the inadequate classification criteria for IIM. To address this, the International Myositis Classification Criteria Project (IMCCP) was established with the aim to develop and validate new classification criteria for IIM and major subgroups of IIM. Clinical and laboratory data from 1600 IIM and comparator cases have been collected. Dissimilarities in disease manifestations among different patient groups have to be considered as classification criteria must be uniformly valid. Little, however, is known about these differences in relation to clinical phenotype for IIM. The aim of this study was to investigate ethnic or gender differences in clinical manifestations in adult DM, juvenile DM (JDM) and amyopathic DM (ADM).

Methods:

We extracted data on serology, 23 muscle variables (e.g., pattern of muscle weakness) and 14 skin manifestations from the IMCCP database and assessed their prevalence among 238 DM, 233 JDM and 45 ADM patients. Comparisons were made between genders and patients of Caucasian and Asian origin. Correction for multiple testing was performed yielding a p<0.0009 for statistical significance.

Results:

Comparisons between the two ethnic groups revealed significant differences in clinical phenotypes. For adult DM cases, several muscle variables were more prevalent among Caucasians compared to Asians and two, neck flexor weakness and muscle tenderness, remained statistically significant after correction for multiple testing. Moreover, the pattern of skin manifestations differed greatly between adult DM patients, and photodistributed violaceous erythema was found to be significantly more prevalent among Caucasians (p<0.0001). Fewer ethnic differences for JDM cases were found and none remained statistically significant after correction for multiple testing. As expected, the ADM patients displayed virtually no muscle manifestations and no significant differences were found. Comparison between prevalence of skin manifestations for Caucasian and Asian ADM patients showed a higher prevalence for most skin variables in Caucasians, where periungual erythema remained statistically significant after correction for multiple testing (p<0.00001). Autoantibody analyses revealed a difference only among JDM cases where rheumatoid factor (RF) was more prevalent in Asians than in Caucasians, but only with a p<0.05.

Gender analyses for serology, muscle variables and skin manifestations revealed fewer differences compared to ethnic differences, and none remained statistically significant after correction for multiple testing.

Conclusion:

We found significant ethnic differences in clinical phenotypes for DM patients. Comparable analyses showed no significant gender differences. Results from this study are of importance for the continued work in defining diagnostic and classification criteria as well as defining inclusion criteria in clinical trials.

To cite this abstract, please use the following information:
Tjarnlund, Anna, Rider, Lisa G., Miller, Frederick W., Werth, Victoria P., Pilkington, Clarissa A., de Visser, Marianne, et al; Ethnic but not Gender Differences in Disease Manifestations in Dermatomyositis Patients. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :235
DOI:

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