Dr. Serrao, how does Lyme arthritis typically present, and are there aspects of this case that make you suspect the diagnosis? Does the serum Lyme test give us any additional information?
►Dr. Serrao: Lyme arthritis is a late manifestation of Lyme disease. Patients typically have persistent or intermittent arthritis, and large joints are more commonly impacted than small joints. Monoarthritis of the knee is the most common, but oligoarthritis is possible as well. The swelling usually begins abruptly, lasts for weeks to months, and effusions typically recur quickly after aspiration. These findings are consistent with the patient’s clinical history.
For diagnostics, the IgG Western blot is positive if 5 of the 10 bands are positive.9 This patient far exceeds the IgG band number to diagnose Lyme disease. All patients with Lyme arthritis will have positive IgG serologies since Lyme arthritis is a late manifestation of the infection. IgM reactivity may be present, but are not necessary to diagnose Lyme arthritis.10 Synovial fluid is often not analyzed for antibody responses as they are susceptible to false positive results, but synovial PCR testing like this patient had detects approximately 70% of patients with untreated Lyme arthritis.11 However, PCR positivity does not necessarily equate with active infection. Serologic testing for Lyme disease by enzyme-linked immunosorbent assay and Western blot as well as careful history and the exclusion of other diagnoses are usually sufficient to make the diagnosis.
► Dr. Merz: On further history the patient reported that 5 years prior he found a tick on his skin with a bull’s-eye rash. He was treated with 28 days of doxycycline at that time. He did not recall any tick bites or rashes in the years since.
Dr. Serrao, is it surprising that he developed Lyme arthritis 5 years after exposure and after being treated appropriately? What is the typical treatment approach for a patient like this?
►Dr. Serrao: It is atypical to develop Lyme arthritis 5 years after reported treatment of what appeared to be early localized disease, namely, erythema migrans. This stage is usually cured with 10 days of treatment alone (he received 28 days) and is generally abortive of subsequent stages, including Lyme arthritis. Furthermore, the patient reported no symptoms of arthritis until recently since that time. Therefore, one can argue that the excessively long span of time from treatment to these first episodes of arthritis suggests the patient could have been reinfected. When available, comparing the types and number of Western blot bands (eg, new and/or more bands on subsequent serologic testing) can support a reinfection diagnosis. A delayed postinfectious inflammatory process from excessive proinflammatory immune responses that block wound repair resulting in proliferative synovitis is also possible.12 This is defined as the postinfectious, postantibiotic, or antibiotic-refractory Lyme arthritis, a diagnosis of exclusion more apparent only after patients receive appropriate antibiotic courses for the possibility of untreated Lyme as an active infection.12
Given the inherent diagnostic uncertainty between an active infection and posttreatment Lyme arthritis syndromes, it is best to approach most cases of Lyme arthritis as an active infection first especially if not yet treated with antibiotics. Diagnosis of postinflammatory processes should be considered if symptoms persist after appropriate antibiotics, and then short-term use of disease-modifying antirheumatic drugs, rather than further courses of antibiotics, is recommended.