Objective: Few factors have consistently been linked to antibiotic-refractory Lyme arthritis (ARLA). We sought to identify clinical and treatment factors associated with pediatric ARLA.
Methods: We performed a case-control study in 3 pediatric rheumatology clinics in a Lyme-endemic region (2000-2013). Eligible children were aged ≤ 18 years with arthritis and had positive testing for Lyme disease by Western blot. Cases were 49 children with persistently active arthritis despite ≥ 8 weeks of oral antibiotics or ≥ 2 weeks of parenteral antibiotics; controls were 188 children whose arthritis resolved within 3 months of starting antibiotics. We compared preselected demographic, clinical, and treatment factors between groups using logistic regression.
Results: Characteristics positively associated with ARLA were age ≥ 10 years, prolonged arthritis at diagnosis, knee-only arthritis, and worsening after starting antibiotics. In contrast, children with fever, severe pain, or other signs of systemic inflammation were more likely to respond quickly to treatment. Secondarily, low-dose amoxicillin and treatment nonadherence were also linked to higher risk of ARLA. Greater antibiotic use for children with ARLA was accompanied by higher rates of treatment-associated adverse events (37% vs 15%) and resultant hospitalization (6% vs 1%).
Conclusion: Older children and those with prolonged arthritis, arthritis limited to the knees, or poor initial response to antibiotics are more likely to have antibiotic-refractory disease and treatment-associated toxicity. Children with severe symptoms of systemic inflammation have more favorable outcomes. For children with persistently active Lyme arthritis after 2 antibiotic courses, pediatricians should consider starting antiinflammatory treatment and referring to a pediatric rheumatologist.
Keywords: EPIDEMIOLOGIC STUDIES; LYME ARTHRITIS; PEDIATRIC ARTHRITIS; RISK FACTORS.