Myositis-Associated Autoantibodies in Juvenile Dermatomyositis

Background: Juvenile Dermatomyositis (jDM) is a rare inflammatory disease in children characterized by muscle weakness and skin involvement. Clinical symptoms and response to therapy are variable, and its prognosis is often difficult to predict. Myositis–associated autoantibodies can be found in patients with jDM, but their significance is not well known.

Methods: We analyzed clinical data, laboratory findings and muscle pathology in in a smaller group of patients with jDM, ranging in age from 4 to 14 years, and related the results with autoantibody findings.

Results: A total of nine patients had proximal muscle weakness; six of the nine patients had muscle pain, and six of the nine had signs of skin involvement. In six patients, determination of myositis-associated autoantibodies showed positive Anti-Jo1 (n = 1), Ro-52 (n = 1), NXP2 (n = 1), nRNP/Sm 9,2 (n = 1), nRNP/Sm-Ak 8,9 (n = 1) and PL-7, and Ro52 (n = 1). A good response to steroids was observed in the patients with NXP2 and nRNP/Sm-Ak 8,9 AB antibodies, whereas the patient with Anti-Jo1 AB did not respond. Muscle biopsies taken from eight patients revealed highly variable findings. Two of the eight patients displayed only a perifascicular atrophy. Deposits of membrane attack complex C5b-9 on endomysial capillaries were seen in four of the eight patients and MHC1 overexpression on myofibers were present in all the eight patients.

Conclusion: The data show that myositis associated autoantibodies can be frequently detected in patients with jDM, but different autoantibodies are found, Determination of myositis-associated autoantibodies seems to be meaningful in patients with jDM, but analysis of a larger cohort of patients is necessary to evaluate the impact of autoantibodies on muscle pathology and disease progression.