Erythema Migrans: Course and Outcome in Patients Treated With Rituximab

Background Information on Lyme borreliosis (LB) in patients treated with rituximab is limited to individual case reports. Methods We reviewed data on adult patients diagnosed with typical erythema migrans (EM) at the LB outpatient clinic of the University Medical Center Ljubljana, Slovenia, in the 10-year period 2008–2017. For all patients, clinical and laboratory information was acquired prospectively using a standardized questionnaire. Results Among 4230 adult patients with a diagnosis of EM, 7 patients (0.17%), 5 women and 2 men with a median age of 65 years (range, 55–66 years), were receiving rituximab for an underlying medical condition. In these 7 patients, signs of disseminated LB (43%) and the isolation rates of borreliae from blood before antibiotic treatment (40%) were unusually high compared with corresponding findings in immunocompetent patients who had EM diagnosed at the same institution (8% vs <2%, respectively). The rates of LB-associated constitutional symptoms and borrelial antibodies in serum were lower than expected (14% and 29%, respectively, in patients receiving rituximab vs 25% and 65% in immunocompetent patients). One of the 7 patients (14%) experienced treatment failure; nevertheless, the outcome of early LB 1 year after antibiotic treatment, as used for immunocompetent patients with EM, was excellent in all 7 patients. Conclusions Findings in 7 patients with EM who were receiving rituximab for underlying disease suggest that although early LB in these patients is more often disseminated than in immunocompetent patients, the outcome 1 year after antibiotic treatment, as used for immunocompetent patients, is excellent.