Background Southern Norway is an endemic area for Lyme borreliosis. IgG antibodies against Borrelia burgdorferi sensu lato (Bb) has been found in approx. 20% of the population (1). The main attention in Norway has been on neuroborreliosis (2). Despite the fact that arthritis is a well-known manifestation of Bb infection there is a lack of data on Lyme arthritis (LA).

Objectives To characterize patients suggestive of having LA in southern Norway.

Methods According to protocol patients aged 18 years or older with arthritis with a positive serology for Bb infection (IgG and/or IgM) suspicious of having LA were consecutively recruited either from general practitioners or from our own department.

Results From January 2007 to December 2010 a total of 27 patients were included. Mean age was 56 years (41–80). Mean symptom duration prior to assessment at department of rheumatology was 11.2 weeks. A history of prior erythema migrans was reported from 7 patients and a known prior tick-bite in 7 patients. Based on overall clinical judgment and Bb diagnostics, 16 patients were classified to have high certainty for LA, 5 to have possible LA and 6 patients were found to have other diagnoses (rheumatoid arthritis 2, psoriasis arthritis 2 and knee osteoarthritis 2).

Among the 21 LA patients 20 had mono-arthritis (knee 18, ankle 2) and 1 had polyarthritis. Mean ESR was 31 mm/hr (8-68), CRP 43 mg/L (1-132) and mean white cell count in synovial fluid available from 14 patients was 18 G/L (0-101). Mean level of serum IgG antibodies was 1800% of cut off (700-2550) 8 Patients were IgM positive, 2 patients had inconclusive IgM test. In two LA patients serology results were missing, they were included due detection of Bb in synovial fluid by PCR. Bb DNA was detected in synovial fluid from 12/21 patients by PCR.

Among the LA patients 20 were treated with doxycycline for 2-6 weeks and one with cloxacilline and cefotaxime for 14 days each. 7 LA patients had intraarticular glucocorticoid (GC) injection prior to and 1 during antibiotic treatment. All patients responded favorable to GC injection however all relapsed.

After first antibiotics had been given 11/16 of patients with a high certainty of having LA had no, 3/16 had one and 2/16 patients had 2 relapses. After antibiotic treatment none developed chronic arthritis. Among the patients with possible LA, 2/5 had no relapse, 1/5 had one relapse and 2/5 got recurrent episodes of joint effusion. These two patients also had severe osteoarthritis.

Conclusions The predominant clinical presentation of LA in Norwegian adults is mono-arthritis of the knee. None of the patients with high certainty for LA developed chronic arthritis. The detection of Bb by PCR helps to diagnose LA in an endemic area. Our experience is that Lyme disease in Southern Norway is a rather benign disease and may successfully be treated with antibiotics even in patients treated with CS prior to antibiotics.

• [1] Mygland et al. Eur J Neurol 2006;13:1213–5.

• [2] Ljostad et al. Lancet Neurol. 2008;7:690-5.

Disclosure of Interest None Declared