398. Description of a Large Pediatric Lyme Arthritis Cohort in an Endemic Region

BACKGROUND: In endemic areas, Lyme arthritis (LA) is a leading cause of joint swelling. Due to the shared inflammatory nature and common clinical features, acute LA is often misdiagnosed as septic arthritis (SA) while recurrent disease is at times difficult to differentiate from other causes of chronic arthritis. In Minnesota, there has been a steady increase in cases of Lyme disease. This has not been met by a clear guideline and there is no consensus for the management of pediatric arthritis. In this context, we sought to characterize the epidemiology and clinical presentation of a large local cohort. METHODS: This is a retrospective review of medical charts from children with confirmed LA, presented at a large academic medical organization in the Upper Midwest between January 2011 to December 2017. Demographic, clinical, and laboratory data were collected and analyzed. RESULTS: Lyme arthritis was confirmed in 109 children. Acute presentation was more common (67) while the rest (42) had either persistence or reoccurrence of symptoms [Figure 1]. Elevated inflammatory markers and synovial pleocytosis were common, unlike fever and refusal to bear weight which were seen occasionally [Figure 2]. Seasonal distribution and the clinical setting for initial presentation as well as admissions are summarized in Figure 3. The knee was involved in all but 2 patients, both had acute monoarthritis (elbow and hip) [Figure 4]. CONCLUSION: LA causes a spectrum of disease, is seen year round, and across the clinical setting continuum. Acute knee monoarthritis is the most common presentation (54% in our cohort) and is often misdiagnosed as SA leading to unnecessary hospitalizations and aggressive interventions. This occurs more frequently at the ED setting and for children with significant synovial pleocytosis. When evaluating a child with arthritis, laboratory findings are none specific and should be used in caution. Pediatric providers in endemic regions, especially those in primary, hospital, or emergency care must be familiar with the clinical presentation and have a high index of suspicion for LA in order to prevent mismanagement. [Image: see text] [Image: see text] [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.