ObjectiveTo investigate the characteristics and risk factors of a novel parenchymal lung disease (LD), increasingly detected in systemic juvenile idiopathic arthritis (sJIA).MethodsIn a multicentre retrospective study, 61 cases were investigated using physician-reported clinical information and centralised analyses of radiological, pathological and genetic data.ResultsLD was associated with distinctive features, including acute erythematous clubbing and a high frequency of anaphylactic reactions to the interleukin (IL)-6 inhibitor, tocilizumab. Serum ferritin elevation and/or significant lymphopaenia preceded LD detection. The most prevalent chest CT pattern was septal thickening, involving the periphery of multiple lobes ± ground-glass opacities. The predominant pathology (23 of 36) was pulmonary alveolar proteinosis and/or endogenous lipoid pneumonia (PAP/ELP), with atypical features including regional involvement and concomitant vascular changes. Apparent severe delayed drug hypersensitivity occurred in some cases. The 5-year survival was 42%. Whole exome sequencing (20 of 61) did not identify a novel monogenic defect or likely causal PAP-related or macrophage activation syndrome (MAS)-related mutations. Trisomy 21 and young sJIA onset increased LD risk. Exposure to IL-1 and IL-6 inhibitors (46 of 61) was associated with multiple LD features. By several indicators, severity of sJIA was comparable in drug-exposed subjects and published sJIA cohorts. MAS at sJIA onset was increased in the drug-exposed, but was not associated with LD features.ConclusionsA rare, life-threatening lung disease in sJIA is defined by a constellation of unusual clinical characteristics. The pathology, a PAP/ELP variant, suggests macrophage dysfunction. Inhibitor exposure may promote LD, independent of sJIA severity, in a small subset of treated patients. Treatment/prevention strategies are needed.

Background Noninvasive estimation of the degree of inflammation seen on kidney biopsy with lupus nephritis (LN) remains difficult. The objective of this study was to develop a Renal Activity Index for Lupus (RAIL) that, based solely on laboratory measures, accurately reflects histological LN activity. Methods We assayed traditional LN laboratory tests and 16 urine biomarkers (UBMs) in children (n=47) at the time of kidney biopsy. Histological LN activity was measured by the NIH Activity Index (NIH-AI) and the Tubulointerstitial Activity Index (TIAI). High LN-activity status (vs. moderate/low) was defined as NIH-AI scores > 10 (vs. ≤ 10) or TIAI scores >5 (vs. ≤ 5). RAIL algorithms that predicted LN-activityNIH-AI and LN-activityTIAI status were derived by stepwise multivariate logistical regression, considering traditional biomarkers and UBMs as candidate components. The accuracy of the RAIL for discriminating by LN-activity status was determined. Results The differential excretion of six UBMs (NGAL, MCP-1, ceruloplasmin, adiponectin, hemopexin, KIM-1) standardized by urine creatinine was considered in the RAIL. These UBMs predicted LN-activityNIH-AI status with >92% accuracy and LN-activityTIAI status with >80% accuracy. RAIL accuracy was minimally influenced by concomitant LN damage. Accuracies between 71 and 85% were achieved without standardization of the UBMs. The strength of these UBMs to reflect LN-activity status was confirmed by principal component and linear discriminant analyses. Conclusion The RAIL is a robust and highly accurate noninvasive measure of LN-activity. The measurement properties of the RAIL, which reflect the degree of inflammatory changes as seen on kidney biopsy, will require independent validation.

Objective To investigate characteristics and risk factors of a novel parenchymal lung disease, increasingly detected in systemic juvenile idiopathic arthritis (sJIA). Methods In a multi-center retrospective study, 61 cases were investigated, using physician-reported clinical information and centralized analyses of radiologic, pathologic and genetic data. Results Lung disease (LD) was associated with distinctive features, including acute erythematous clubbing and a high frequency of anaphylactic reactions to the IL-6 inhibitor, tocilizumab. Serum ferritin elevation and/or significant lymphopenia preceded LD detection. The most prevalent chest CT pattern was septal thickening, involving the periphery of multiple lobes +/- ground glass opacities. Predominant pathology (23/36) was pulmonary alveolar proteinosis and/or endogenous lipoid pneumonia (PAP/ELP), with atypical features, including regional involvement and concomitant vascular changes. Apparent severe delayed drug hypersensitivity occurred in some cases. 5-year survival was 42%. Whole-exome sequencing (20/61) did not identify a novel monogenic defect PAP-related or macrophage activation syndrome (MAS)-related mutations as likely primary cause. Trisomy 21 (T21) increased LD risk, as did young sJIA onset. Refractory sJIA was not required for LD development. Exposure to interleukin (IL)-1 and IL-6 inhibitors (46/61) was associated with multiple LD features. By several indicators, severity of sJIA was comparable in drug-exposed subjects and published sJIA cohorts. MAS at sJIA onset was increased in the drug-exposed, but it was not associated with LD features. Conclusions A rare, life-threatening LD in sJIA is defined by a constellation of unusual clinical characteristics. The pathology, a PAP/ELP variant, suggests macrophage dysfunction. Inhibitor exposure may promote LD, independent of sJIA severity, in a small subset of treated patients. Treatment/prevention strategies are needed.