Autoantibody Profile of Children with Juvenile Dermatomyositis.

Objective: To study autoantibody profile in juvenile dermatomyositis (JDM) and to look for phenotypic associations of these autoantibodies, if any.

Methods: Thirty-four children with JDM with a minimum follow-up duration of 24 mo were enrolled. Clinical findings and investigations at the time of diagnosis were noted from the clinic records. At inclusion, they were clinically evaluated for residual disease, disease activity and complications. All the enrolled patients were tested for antinuclear antibodies (ANA), muscle specific antibodies (MSA) and myositis associated autoantibodies (MAA).

Results: ANA positivity was seen in 14/34 children. At least one MSA or MAA was present in 8/34 children. Anti-SRP, anti-MDA-5, and anti-Mi-2 antibodies were present in 4, 3, and 1 patient, respectively. Anti-SSA/Ro52 antibody was positive in 1 child. All four children with anti-SRP antibody were girls, who had polycyclic course. Two of them developed calcinosis. Prominent skin involvement with less severe muscle involvement and monocyclic course were seen in patients with anti-MDA-5 antibody. Two of them had arthritis/arthralgia at initial presentation. The only patient with anti-Mi-2 had normal muscle strength at enrollment. None of the patients had anti-synthetase antibodies (anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ), anti-Ku, anti-Scl-70, anti-NXP-2 or anti-HMG CoA.

Conclusion: Eight patients tested positive for at least one MSA or MAA. The prevalence of autoantibodies was low. Positivity for anti-SRP, anti-MDA-5, anti-Mi-2 and anti-SSA/Ro52 antibodies was seen in 4, 3, 1 and 1 patients, respectively. Ethnic differences and testing for autoantibodies during/after therapy could be responsible for the low positivity rate for autoantibodies.