Anti-melanoma differentiation-associated gene 5 antibody associated rapidly progressive interstitial lung disease in a pediatric patient: a case report.

Abstract

Background: Rapidly progressive interstitial lung disease presents as a severe complication of juvenile dermatomyositis, particularly when associated with anti-melanoma differentiation-associated gene 5. We report a pediatric case that underscores the necessity for clinicians to maintain a high index of suspicion for early identification and management.

Case presentation: A previously healthy 7-year-old White girl presented with a 6-week history of generalized weakness, fever, joint pain, and abdominal pain. Initial examination revealed hypoxia, tachypnea, and hepatosplenomegaly. Laboratory tests were marked by thrombocytopenia, lymphopenia, elevated liver enzymes, high ferritin, high triglyceride, elevated muscle enzymes, and increased soluble IL-2 receptor, suggesting macrophage activation syndrome that was and managed with dexamethasone 5 mg/kg/m² twice daily. There were no pathogenic skin features of juvenile dermatomyositis, except for nailfold capillary dropout. Initial cell counts revealed that her white blood cell count was 2.87 × 10⁹/L, hemoglobin was 105 g/L, platelet was 90 × 10⁹/L, and ferritin was 2000.6 μg/L and antinuclear and anti-Ro52 antibodies were positive. She was noted to have peripheral muscle weakness. Her clinical course was marked by progressive respiratory failure requiring mechanical ventilation with imaging revealing diffuse alveolar ground-glass opacities. The infectious work up was negative for bacterial, fungal, and viral ethologies including Epstein-Barr virus; hepatitis A virus, hepatitis B, hepatitis C, and hepatitis E viruses; parvovirus B19; cytomegalovirus; herpes simplex virus 1 and 2; and human herpesvirus 6. With the interstitial lung disease picture, pulse doses of intravenous methylprednisolone and intravenous immunoglobulin were initiated. She developed a significant air leak that was managed with bilateral chest tubes. Her significant hypoxemia required cannulation to veno-venous extracorporeal membrane oxygenation. The diagnosis of anti-melanoma differentiation-associated gene 5 antibody-associated juvenile dermatomyositis was confirmed by antibody testing. Additional immunomodulatory therapy was utilized during the treatment course with no noted improvement. She was not a candidate for lung transplantation, and in the face of additional organ dysfunction, life-sustaining therapies were withdrawn on day 32 of intensive care unit admission.

Conclusions: This case demonstrates the diagnostic and therapeutic challenges in patients with rapidly progressive interstitial lung disease in the context of anti-melanoma differentiation-associated gene 5 associated juvenile dermatomyositis, who may not present with overt muscle and cutaneous features of juvenile dermatomyositis and whose lung disease can progress very rapidly. A high index of suspicion among clinicians is critical, and expedited diagnostic serology may assist with earlier diagnosis and initiation of therapy. Extracorporeal membrane oxygenation can be utilized as a bridge to diagnosis in the setting of severe refractory hypoxemic respiratory failure. However, despite aggressive treatment, the prognosis remains challenging.