Elevated liver enzymes: unusual presentation of anti-MDA5 antibody-associated juvenile dermatomyositis.

Anti-melanoma differentiation-associated gene 5 antibody positive juvenile dermatomyositis (Anti-MDA5 JDM) is a subtype of JDM characterized by cutaneous ulcerations, arthritis, weight loss and progressive interstitial lung disease that can lead to significant morbidity and mortality, often warranting early aggressive treatment. It can present without the classical features of JDM (proximal muscle weakness, heliotrope rash and Gottron’s papules), making diagnosis challenging. We describe a 4-year-old male with Anti-MDA5 JDM who presented with significantly elevated liver enzymes, arthralgia, ecchymotic macules, oral ulcers, and intermittent fevers without significant muscle weakness whose unusual presentation delayed his diagnosis and treatment. He underwent extensive work-up for differential diagnoses including multisystemic inflammatory syndrome in children, non-accidental trauma, and autoimmune hepatitis. His liver biopsy showed extensive hepatocyte swelling and focal hepatocyte cholestasis which has been described in Anti-MDA5 dermatomyositis in adults. His ecchymotic macules progressed to ulcers, and skin biopsy showed perivascular and periadnexal dermatitis with increased mucin deposits, seen in autoimmune connective tissue diseases. He eventually developed arthritis, and mild muscle weakness in bilateral shoulders. Right deltoid muscle biopsy showed atrophic and degenerative myofibers and inflammation consistent with immune-mediated myopathy. His myositis-specific autoantibody profile came back positive for Anti-MDA5, enabling the specific diagnosis of Anti-MDA5 JDM. This case illustrates that definitive diagnosis of Anti-MDA5 JDM can be challenging due to unusual presentations such as elevated liver enzymes and illustrates the importance of further studies to understand the different clinical manifestations of Anti-MDA5 JDM.