Systemic juvenile idiopathic arthritis (sJIA)-associated lung disease is distinct from other inflammatory lung conditions, according to the results of new study. In patients with sJIA attending the Cincinnati Children’s Hospital Medical Center, the presence of lung disease was associated with a young age of diagnosis, a history of macrophage activation syndrome and prior adverse reactions to cytokine-targeted biologic therapy. Lung disease in these patients shared some histopathological features with pulmonary alveolar proteinosis but had different immunological features, including increased IL-18.