Background/Purpose: A subset of juvenile dermatomyositis (JDM), clinically amyopathic dermatomyositis (CADM), is uncommon and mainly described in adults. CADM is classically characterized by skin ulcerations, minimal muscle involvement, and interstitial lung disease (ILD). Anti-MDA5 antibodies are associated with CADM and ILD. A subset of anti-MDA5 patients have rapidly progressive ILD (RP-ILD), that is typically fatal. Limited data exists on pulmonary manifestations of these presentations in pediatric patients. We aimed to describe pulmonary manifestations, as well as outcomes, in a cohort of patients with pediatric anti-MDA5-associated lung disease.

Methods: A retrospective chart review was completed on patients < 18 years of age at presentation with the diagnosis of JDM, ILD and positive anti-MDA5 antibodies.

Results: 10 patients were identified: 60% male, 70% White, 30% Black, 40% Hispanic. The mean age at symptom onset was 9.6±6.8 years, at diagnosis it was 10±6.8 years. The systems affected at initial presentation were integumentary (100%), musculoskeletal (90%) and respiratory (60%). 40% presented without respiratory symptoms, but were subsequently found to have lung disease. Skin manifestations included nonspecific erythema (70%), Gottron’s papules (60%), ulcerations (50%) and heliotrope rash (40%). Musculoskeletal symptoms included arthritis (80%), mild weakness (60%), and muscular tenderness (50%). Mean creatine kinase was 92.7±69.3 units/L.

Respiratory symptoms at presentation included shortness of breath (67%), cough (67%), chest pain (33%), and wheezing (17%). Four patients required respiratory support; 1 nasal cannula, 1 high frequency oscillatory ventilation and 2 extracorporeal membrane oxygenation (ECMO). All patients had abnormal chest CT; findings included consolidation(s) (60%), pneumomediastinum (50%), ground glass opacities (50%), and nodules (30%). 8 patients had pulmonary function testing showing a diffusion defect in 75% and a restrictive pattern in 25%. At last follow-up (range 6 months-5 years), diffusion defects (60%) and dyspnea on exertion (30%) were still noted. All 3 patients with RP-ILD were toddlers at presentation (16, 21, and 25 months). 2 of the 3, both those requiring ECMO, died due to respiratory failure and diffuse alveolar damage refractory to extensive immunomodulatory therapy. The surviving patient with RP-ILD required mechanical ventilation for 14 months, but is now well off all therapies for 4 years. Treatment ranged: more than 1 patient was treated with corticosteroids (100%), hydroxychloroquine (70%), IVIG (50%), methotrexate (50%), rituximab (40%), azathioprine (40%), plasma exchange (30%), NSAIDs (10%), mycophenolate mofetil (10%), and cyclophosphamide (10%).

Conclusion: The pediatric presentation of anti-MDA5-associated CADM is similar to the adult disease, patients had skin ulcerations and lung disease, but minimal muscle involvement. Pneumomediastinum was common. RP-ILD was fatal in 2 of 3 cases. There is a need for further studies on this variant of JDM, specifically treatment options and investigations of younger patients who seem to be at higher risk of severe disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-melanoma-differentiation-associated-protein-5-mda5-positive-juvenile-dermatomyositis-focus-on-the-lung/