Lyme disease (LD) is the most reported vector-borne disease in North America, caused by the spirochete Borrelia burgdorferi. In central and eastern Canada, B burgdorferi is transmitted by Ixodes scapularis (the blacklegged tick), and by Ixodes pacificus (the western blacklegged tick) in western Canada. The reported incidence of human LD cases in Canada has increased substantially since 2009.1 The increasing prevalence of B burgdorferi– infected ticks in Canada has important implications for family physicians, particularly those who practise in LD-endemic areas. We present a case of Lyme arthritis (LA) in a child in southeastern Ontario with a 3-year history of recurrent joint pain and swelling.
Case
In December 2015, an 8-year-old boy presented to a pediatric clinic with a 2-week history of painful left knee swelling and difficulty walking. There was no history of injury or trauma. The family reported that he had a mild upper respiratory tract infection 6 weeks previously. The patient was otherwise healthy, without a relevant medical or surgical history such as a history of inflammatory bowel disease. He had a risk of tick exposure, as his family reported frequent camping trips in a Lyme-endemic region. Neither the patient nor his parents recalled him having a tick bite or rash consistent with erythema migrans (EM). He lived in southeastern Ontario and had not traveled outside the region in the previous year. His family history was relevant for juvenile idiopathic arthritis (JIA) and rheumatoid arthritis.
On examination, the child was afebrile, appeared well, and had no difficulties walking. Findings of neurologic and ocular examinations were normal. Examination of the left knee revealed a large effusion with tenderness to palpation but without warmth or erythema. There was full active range of motion, with mild pain at the extremes of flexion and extension. The remainder of the physical examination findings were normal and he had no EM rash. The boy underwent bilateral knee ultrasound scans for suspected reactive arthritis (ReA), which revealed large left and small right effusions with associated regional inflammatory synovitis. Bloodwork results showed mildly elevated inflammatory markers: an erythrocyte sedimentation rate of 45 mm/h and a C-reactive protein level of 21.4 mg/L (Table 1). Test results for antinuclear antibodies were negative. He was diagnosed with presumed viral ReA and was treated with nonsteroidal anti-inflammatory drugs, resulting in gradual pain relief. However, the boy continued to experience recurring joint swelling every few weeks.
In December 2017, the boy returned to his family physician with a history of recurring painful knee swelling in flares lasting 5 to 14 days before resolving. Occasionally his elbow, ankles, and shoulder joints were involved. There was never small joint involvement. On repeat examination he was afebrile and able to walk. The family reported history of a recurring eczematous rash on his abdomen and buttocks. Both knees were tender to palpation and there was mild pain on passive flexion and extension. The remaining physical examination findings were normal.
The boy was referred to a pediatrician for possible JIA or psoriatic arthritis. He was seen in February 2018, 26 months after initial symptom onset. His mother reported that he had become more fatigued over the past year and that his joint symptoms worsened with activity. Findings of a complete physical examination were unremarkable.
A workup was initiated by the consultant pediatrician. Bilateral knee x-ray scans showed no abnormalities. Results of a complete blood count with differential count were normal. Lyme serology tests were done and the results were reactive for immunoglobulin (Ig) M and IgG on enzyme-linked immunosorbent assay, with reactive IgG Western blot results (Table 1). The boy was diagnosed with LA and prescribed amoxicillin for 21 days. He was referred to the pediatric rheumatology department for further evaluation.
In April 2018, the patient was seen in the pediatric rheumatology department and was still experiencing episodic oligoarthritis of the large joints, with limitations to function and ongoing fatigue. Given his ongoing symptoms, doxycycline was prescribed for 28 days. At follow-up in July 2018, all symptoms had resolved and examination findings were normal.
Laboratory values: Bolded values indicate clinically important results or results outside the reference range.
Differential diagnosis
One of the challenges in diagnosing pediatric LA is differentiating it from other causes of infectious or inflammatory arthritis, namely septic arthritis, acute ReA, and nonsystemic-onset JIA. The main clinical features of each are listed in Table 2.2-6
Pediatric clinical presentations for LA, septic arthritis, ReA, and JIA
Discussion
There are 3 main clinical stages of LD.7 The early localized stage develops within 30 days of infection and is characterized by EM, a generally asymptomatic expanding erythematous patch, with or without central clearing, measuring greater than 5 cm. Erythema migrans might be accompanied by nonspecific flulike symptoms. If early LD goes unrecognized and untreated, or there are no specific clinical symptoms, patients might progress to early disseminated disease 1 to 3 months after infection. This stage can include multiple EM, severe headaches, neck stiffness, fatigue, neurologic symptoms (cranial neuropathy, radiculopathy, lymphocytic meningitis), or carditis (heart block). Should infection go untreated for longer than 3 months, symptoms of late disseminated LD might occur and last for months or years, with arthritis being the most common late disseminated manifestation in children.
Lyme arthritis most commonly presents as monoarticular arthritis, often affecting large joints, particularly the knees; oligoarticular and polyarticular involvement can also be observed.3 Affected joints are typically markedly swollen and mildly tender, with minimal effect on walking. Recurrence of LA is frequent in the same joint, but other joints might become affected. Lyme arthritis should be considered in all cases of pediatric arthritis where the patient has had possible tick exposure. Serologic testing is the mainstay for differentiating LA from other arthritides.3 However, even with reactive Lyme serology results, other causes of arthritis are possible.
When there is high clinical suspicion of LA supported by a history of EM or possible tick exposure, 2-tier serology testing for B burgdorferi might be ordered.8 Dependent on pretest probability, a reactive enzyme-linked immunosorbent assay result followed by a reactive immunoblot test result establishes the diagnosis of LD. Initiation of antibiotic treatment can be considered while waiting for results if there is high clinical suspicion of LD.8 The recommended treatment for LA in children 8 years of age and older is 28 days of doxycycline or β-lactams.9 The long-term prognosis of appropriately treated LA in children is excellent.10 In pediatric patients who continue to experience mild residual joint swelling after the initial course of treatment, the oral antibiotic regimen might be repeated.9 A small percentage of patients might experience persistent arthritis for months or years despite appropriate treatment for LA, and their symptoms can be successfully managed with nonsteroidal anti-inflammatory drugs.3
Unfortunately, the diagnosis of LD might have been delayed in this case. Although the child was initially prescribed an appropriate course of antibiotics to treat early LD, it does not follow the guideline recommendation of 28 days for LA.9 Physicians should be aware of their local LD epidemiology, take a history of travel and possible tick exposure, and understand the various clinical presentations of this emerging infection. Lyme arthritis should be considered in patients with possible tick exposure who present with inflammatory oligoarthritis that might be fluctuating and migratory. In Ontario, approximately 42% of patients with LD report arthritic symptoms11; children are more likely than adults are to develop arthritis as their first LD manifestation.12,13 In 30% of LD cases, patients do not recall a history of a tick bite14 and EM might not be present; in fact, up to 79% of children with LA do not recall a rash.13
Clinical and laboratory-confirmed cases of LD are reportable to local public health agencies.15 There are several resources available to help physicians identify, diagnose, and manage LD and educate patients on the risk and prevention of LD (Box 1).
Conclusion
Our case highlights the importance of differentiating LA from other possible causes of similar presentations. Physicians should have a high index of suspicion for LA in a child (or adult) who presents with a first episode or recurring arthritis in a Lyme-endemic region.
Notes
Editor’s key points
▸ Two-tier serologic testing is the mainstay for differentiating Lyme arthritis (LA) from other arthritides.
▸ Presentation of LA is more common in children than adults and most often involves the knee. Physicians should have a high index of suspicion for LA in a child (or adult) who presents with a first episode or recurring arthritis.
▸ The absence of a known tick bite or erythema migrans rash does not exclude the possibility of Lyme disease. In fact, most LA patients will not recall having had either.
▸ Cases with erythema migrans associated with Lyme disease– endemic regions, or laboratory-confirmed cases with a compatible clinical history, should be treated with antibiotics in accordance with expert guideline recommendations.
Footnotes
Competing interests
None declared
This article has been peer reviewed.
Cet article a fait l’objet d’une révision par des pairs. Can Fam Physician 2020;66:820-3
- Copyright© the College of Family Physicians of Canada
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