291 Juvenile dermatomyositis associated with interstitial lung disease: would anti-MDA5 antibody detection improve early diagnosis and management?

Background: We describe a case of anti-MDA5 antibody positive juvenile dermatomyositis (JDM) associated with interstitial lung disease (ILD) and propose early antibody detection may guide management and improve outcome. Methods: A 15-year-old male presented with a three month history of pain and stiffness in his right ankle, left knee and hand joints associated with mild weakness. A blistering rash on his extremities developed into classical JDM facial rash with periorbital swelling, gottren papules and paranychial ulcers. Initial investigations included: EMG study showing myopathy; MRI buttock and skin biopsy both consistent with dermatomyositis (Table 1). He started hydroxychloroquine, weekly methotrexate injections and high dose prednisolone including fortnightly three-day intravenous pulses. Results: Within one month, he developed a knee staphylococcus aureus arthritis which required prolonged antibiotics. Despite minimal respiratory symptoms, his lung function test showed a restrictive pattern with reduced diffusion (FVC-7.57 predicted, TLC-4.18, and DLCO 2.2). ILD with patchy consolidation was confirmed on imaging. IV immunoglobulins (IVIG) were added. Two week later, he developed chest pain and shortness of breath, with clinical signs of surgical emphysema confirmed radiologically, with apical pneumothoraces, pneumomediastinum and pneumopericardium. The air leaks were secondary to bronchial perforations secondary to JDM related ILD. Although the rash, arthritis and myositis responded to treatment, his ILD progressed. He required admission to PICU for respiratory support and was covered for infection including pneumocystis pneumonia. Further IVIG and IV methylprednisolone was given and mycophenolate commenced. However, his deterioration necessitated ventilation and transfer for ECMO. His bloods showed anti-MDA5 positive antibodies. Plasmapharesis, cyclophosphamide and rituximab were given but despite best efforts, he died from ILD secondary to JDM.