Differentiating Clinical Presentations of Lyme Arthritis, Septic Arthritis, Toxic Synovitis, and Other Inflammatory Joint Pathologies

BACKGROUND: Lyme arthritis (LA) is a manifestation of Lyme disease characterized by joint swelling and pain. LA's clinical presentation mimics pathologies such as septic arthritis (SA) and toxic synovitis (TS). Despite similar presentations, the treatments vary; LA is treated medically, septic arthritis requires surgical debridement, and TS resolves with conservative therapy. Similar presentations can lead to misdiagnosis, subjecting patients to unnecessary interventions. The purpose of this study was to identify physical and laboratory findings that may help differentiate between LA, SA, and TS. METHODS: Pediatric patients were selected for the study based on ICD-9/10 codes suggestive of an infectious/inflammatory/Lyme-related process. The initial group was filtered to patients who had undergone testing for an infectious process. This group was manually reviewed, and each patient was assigned to a diagnostic category. Relevant patient information was extracted from the medical records. Continuous data were summarized using simple numerical summaries, and categorical data as counts and proportions. RESULTS: In this study, 506 patients were analyzed. Subgroup analysis focused on LA, SA, and TS. Patients with LA had the highest proportion of joint swelling, followed by SA. Pain with short arc motion was most prevalent in the SA group, and they were least likely to bear weight. LA favored the knee, TS the hip, and SA the knee and hip; however, other joints were also involved. SA presented with the highest C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), white blood cell counts, percentage of neutrophils, and cell count values. TS had the lowest elevations in CRP, ESR, percentage of neutrophils, and cell counts, but the highest percentage of lymphocytes, while LA had the highest platelet count. CONCLUSIONS: As Lyme disease continues to spread, clinicians will increasingly encounter patients with LA. Clinicians must differentiate between LA and similar pathologies to ensure appropriate treatment and avoid unnecessary interventions. Key differentiating variables, such as anatomic location, CRP, and ESR, can aid in diagnosis, though there are limitations. Clinicians can use this information to guide treatment decisions for these patients. LEVELS OF EVIDENCE: Level III.