[Juvenile dermatomyositis and new autoantibodies: Cases and review]

Juvenile dermatomyositis (JDM) is the most common inflammatory myopathy in children. Its diagnosis is usually made on a clinical basis following the criteria of Bohan and Peter (1975). Recently, the presence of myositis-specific autoantibodies (MSAs) have started to be associated with specific outcome in adult patients; the diagnosis and prognosis value of these autoantibodies remains to be identified in children. We report four cases of JDM with MSAs focusing on clinical, biological, and radiological manifestations, and then we describe associated treatment. The cohort comprises four girls with an average age of 8.5 years. The time to diagnosis was 1 week to 4 months. For these patients, the immunologic study found one patient positive for the MDA5 antibody (or CADM 140), one positive for the TIF1γ antibody (or p155/140), and two patients positive for the NXP2 antibody (or p140/MJ). Each patient showed specific and characteristic cutaneous manifestations. For example, the girl positive for the TIF1γ antibody presented the most severe skin disease with urticaria, face edema, and vascularity of the neck and shoulders. However, regarding muscular features, proximal weakness was present in most of the cohort, except for the child positive for the MDA5 antibody, who presented no sign of muscular disease at the beginning with low CK levels. Importantly, acute pancreatitis also affected this patient. Concerning radiological indications, muscular MRI evidenced hyperinflammation, a sign of diffuse myositis, in all these patients. Treatments consisted in corticosteroids together with methotrexate or mycofenolate mofetil associated or not with intravenous immunoglobulin therapy. This report highlights the importance of systematic detection and analysis of MSA in diagnosis and characterization of JDM, and describes a new approach that would allow more focused treatments and be a useful predictor of clinical complications and prognosis in JDM-affected subjects.