Few studies have assessed the association between fine particulate matter (PM2.5) exposure during pregnancy and infancy and pediatric rheumatic diseases (PRDs). The goal of this study was to investigate the association of PM2.5 with PRDs, and to explore sensitive windows of exposure. Therefore, we conducted a cohort-based case-control study to investigate the association between weekly exposure to PM2.5 and PRDs in Taiwan. Our birth cohort consisted of infants born in 2004-2014 (n = 1,991,592) who were followed from conception to the end of 2015. There were 2363 cases of incident PRDs in children, and 23,630 children served as controls using density matching (1:10) based on date of birth, gender, and gestational week. We used a linear mixed effect (LME) model to incorporate the aerosol optical depth (AOD), meteorological variables, and land-use data to predict daily PM2.5 concentrations. We also performed conditional logistic regression with distributed lag non-linear models (DLNMs) to assess the effects of weekly average PM2.5 on PRDs, as well as dose-response relationships. In DLNMs, exposure to PM2.5 during pregnancy (11-40 weeks) or infancy (1-14 weeks after birth) was associated with incident PRDs adjusting for potential confounding factors, and for carbon monoxide and sulfur dioxide. In the dose-response association, the odds ratios of PRDs were significantly increased for PM2.5 exposures between 26 and 54 μg/m3. In addition, exposure to PM2.5 above 81 μg/m3 dramatically increased the risk of PRDs. In conclusions, our study provides new data to suggest that PM2.5 exposure from 11-40 gestational weeks to 1-14 weeks after birth can increase the risk for PRDs in a non-linear dose-response fashion.

BACKGROUND: Ultrasonography has become a useful tool in the clinical rheumatology settings in the last two decades, but its use has only recently been explored by pediatric rheumatologists. The aim of this article is to review the literature on the current status and recent advances on the use of ultrasound in pediatric rheumatic diseases.
METHODS: We have retrieved and reviewed the relevant articles from MEDLINE/PubMed databases published so far, on the applications of ultrasound in juvenile idiopathic arthritis (JIA), systemic lupus erythematosus, dermatomyositis, enthesitis, Sjogren\'s syndrome, and other rheumatic diseases. In addition, articles on novel ultrasound imaging technology of potential use in pediatric rheumatology are also reviewed.
RESULTS: In JIA, ultrasound can be used to detect subclinical synovitis, to improve the classification of patients in JIA subtypes, to capture early articular damage, to monitor treatment response, and to guide intraarticular injections. Ultrasound is also considered useful in other rheumatic disorders for the evaluation of musculoskeletal symptoms, assessment of parotid gland pathology, and measurement of skin thickness and pathology. Novel ultrasound techniques developed to augment the functionality of ultrasonography may also be applicable in pediatric rheumatic disorders.
CONCLUSIONS: Ultrasound shows great promise in the assessment and management of children with rheumatologic disorders. However, standardization and validation of ultrasound in healthy children and in patients with rheumatic diseases are still needed.