024. Anti-KU antibodies in two paediatric cases with juvenile dermatomyositis-scleroderma overlap: why is it important to know?

Abstract

Background: Juvenile dermatomyositis (JDM) is a heterogeneous autoimmune-mediated disease characterized by proximal muscle weakness, elevated levels of muscle enzymes, and rashes typically heliotrope rash and Gottron's papules. Serologic investigation has been explored in JDM in order to define subgroups that can help us predict clinical course, treatment and prognosis. Autoantibodies directed against the Ku autoantigen are one of myositis associated antibodies found in adult patients with systemic sclerosis (SSc) and have been associated with myositis overlap and interstitial lung disease (ILD). However, there is a paucity of data on the clinical correlates of anti-Ku antibodies in the paediatric autoimmune conditions. Aims: The aim of this study was to review clinical phenotype, prognosis and treatment of anti-Ku antibodies in two paediatric cases with juvenile dermatomyositis-scleroderma overlap. Methods: 552 of the patients enrolled in the Juvenile Dermatomyositis Cohort and Biomarker Study (JDCBS) were tested for autoantibodies and we found only two cases who have anti-Ku positivity. The review of patient medical notes was performed with the comparison between disease characteristics of anti-Ku antibodies in our patients and other case studies. Results: We report a 10 year old male with anti-Ku associated myositis/scleroderma overlap characterized by destructive myopathy, sclerodermatous rashes, joint restriction, oesophageal dysmotility, interstitial lung disease (ILD) and possible cardiac involvement. The patient initially presented at the age of 8 as a hyperpigmented lesion over the chest and abdomen which developed into a widespread tightening and thickening of the skin. He was started on high dose intravenous steroid, subcutaneous methotrexate injection and courses of Rituximab and cyclophosphamide infusion. His clinical progression has gradually been improving after six doses of cyclophosphamide. The second case is a 10 year old girl with a three year history of gradual tightening of her fingers, progressing to her elbows, shoulders, hips, knees and back. She also complained of Raynaud phenomenon with progressive muscle weakness. After seven years of treatment with steroid and methotrexate, she still suffered from active muscle and skin disease with new vasculitis lesions on all fingers and required more aggressive treatment. Similar to previous adult cohort studies, anti-Ku positive patients are associated with more severe muscle weakness, articular symptoms, Raynaud phenomenon and a tendency to develop ILD. To the best of our knowledge, this report is one of the youngest anti-Ku positive patients with juvenile dermatomyositisscleroderma overlap. Conclusions: Our review supports adult cohort studies that juvenile dermatomyositis patients who have positive anti-Ku antibodies will need to be monitored closely as the concerns of progressive muscle and skin disease with the possibility of developing interstitial lung disease. Prompt treatment should be managed according to the severity of symptoms in order to improve clinical outcome and prevent serious complication. Our report underscores the screening for anti-Ku antibodies at diagnosis in JDM patients presenting with scleroderma features such as Raynaud phenomenon or sclerodactyly to guide further investigation and initiate appropriate treatment.