Lyme disease is caused by Borrelia burgdorferi and can lead to dermatologic, neurologic, cardiac, and musculoskeletal manifestations. The arthritis of Lyme disease is typically monoarticular, with the knee being most commonly involved. Lyme arthritis of small joints has not previously been well described. We report 3 children who presented with sternoclavicular joint swelling and who were found to have Lyme disease based on enzyme-linked immunosorbent assay and Western blot. This description of sternoclavicular Lyme arthritis highlights the importance of considering Lyme disease in the differential and diagnostic workup of new onset, small joint arthritis in patients presenting from or with travel to Lyme endemic regions.

Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted in endemic regions by Ixodes ticks. Reports of Lyme disease in the northeastern United States have increased by as much as 215% between the years 2000–2015,1 with the true incidence of Lyme estimated at 10-fold of reported cases.2 Clinical manifestations of Lyme disease have been traditionally classified into 3 stages: localized, disseminated, and late, with arthritis occurring in disseminated- and late-stage disease.3 The typical presentation of Lyme arthritis involves inflammation of a large joint, with the knee being most commonly involved.4 

Involvement of small joints has not been frequently described in Lyme disease. Thus, when patients present with undiagnosed Lyme-associated small joint arthritis, the clinician generally considers other infectious, rheumatologic, or oncologic diseases in the differential diagnosis. As the incidence of Lyme increases, clinicians need to consider Lyme in the differential diagnosis of small joint disease. In this series, we describe 3 patients who presented with chief complaints involving swelling in the sternoclavicular joint and who were ultimately diagnosed with Lyme disease.

A 16-year-old boy was seen in the emergency department in May with complaints of shoulder pain for 1 day, which he initially had attributed to a pulled muscle. The following day, his mother noted enlargement of his left sternoclavicular joint, which prompted the evaluation. He denied trauma, fever, chills, or shortness of breath. He did report an upper respiratory infection in the previous 2 weeks that had resolved. On examination, he was afebrile and well appearing. He had tenderness, warmth, and swelling over his left sternoclavicular joint. The C-reactive protein (CRP) was elevated at 5.76 mg/dL (normal range <0.8). The erythrocyte sedimentation rate (ESR) was 9 mm/hour and the white blood cell (WBC) count was 11 000 cells per µL.

An MRI of the chest was performed given the elevated CRP. This demonstrated left sternoclavicular joint synovitis suggestive of an inflammatory condition. There was no evidence of osteomyelitis. He was admitted for further evaluation of possible septic joint, and a joint aspiration was performed by interventional radiology. The joint aspirate contained 432 WBCs per millimeter, of which 95% were neutrophils. Lyme enzyme-linked immunosorbent assay (ELISA) of the serum using VlsE-1 and PepC10 antigens was positive for Lyme disease (>5.00), and confirmatory Western blot had positive results for both immunoglobulin G (IgG) (10 out of 10 band cells) and immunoglobulin M (IgM) (2 out of 3 band cells) antibodies. The results from a Lyme polymerase chain reaction (PCR) of the joint aspirate fluid were positive for Lyme disease. The patient was discharged after his joint aspiration did not reveal septic arthritis, and he completed a 28-day course of doxycycline after the positive results of Lyme testing were known, resulting in symptomatic improvement. He remained symptom-free at last follow-up 2 years after treatment.

A 5-year-old boy presented to the emergency department in May after waking up at night with complaints of left shoulder pain. The pain was exacerbated on any movement of the extremity. His mother noted a swelling over the medial aspect of the left clavicle. There was no trauma.

The patient was in no distress on his initial evaluation and was afebrile. His affected extremity and shoulder region were free of deformity, swelling, or tenderness; however, he held his extremity close to his chest. There was tenderness and swelling over the left sternoclavicular joint. Radiographs of the affected shoulder were negative for fracture, joint space widening, or dislocation. Blood count showed a WBC count of 8300 cells per µL, CRP of 0.73 mg/dL, and ESR of 11 mm/hour. An ultrasound performed in the emergency department revealed joint asymmetry without fluid collection. His pain improved with acetaminophen. Given his well appearance and absence of other findings concerning for acute infectious, oncologic, or traumatic process, the patient was discharged from the hospital with instructions to follow-up with rheumatology if the symptoms persisted.

After discharge, the patient’s sternoclavicular swelling resolved in ∼1 week; however, 2 months later the boy had 1 to 2 days of ankle swelling, which also resolved. Approximately 2 weeks after the ankle swelling, he had bilateral knee swelling, which also resolved in 1 to 2 days. He was seen in rheumatology clinic and testing for Lyme serology was performed. Lyme ELISA was >5, and confirmatory IgG (10 out of 10 band cells) and IgM (2 out of 3 band cells) Western blot results were both positive. The patient was prescribed a 28-day course of doxycycline and remained symptom-free at last follow-up 20 months after completion of therapy.

An 11-year-old previously healthy boy was referred to pediatric rheumatology clinic in November for complaints of joint pain and swelling. The symptoms initially began with pain in his left shoulder and elbow, which each lasted for a few days and spontaneously resolved. Approximately 1 month later, he had pain in his right thumb, wrist, elbow, and shoulder, followed by swelling of his right clavicle. The pain was persistent and exacerbated by any movement of his joint and was associated with joint stiffness in his arm. He had been afebrile and free of rashes. He had been more tired since the onset of symptoms.

On examination, the patient was afebrile and well appearing. He had warmth, swelling, and tenderness over the right sternoclavicular joint (Fig 1) and the right elbow. The joints were not erythematous but his shoulder had limited range of motion, secondary to pain.

FIGURE 1

Visible swelling of the right sternoclavicular joint an 11-year-old boy with migratory arthritis, found to be secondary to Lyme disease (patient 3 in this series.) The joint was nonerythematous but tender to touch and associated with painful shoulder movements.

FIGURE 1

Visible swelling of the right sternoclavicular joint an 11-year-old boy with migratory arthritis, found to be secondary to Lyme disease (patient 3 in this series.) The joint was nonerythematous but tender to touch and associated with painful shoulder movements.

Close modal

Laboratory evaluation done by his pediatrician before referral revealed an ESR of 77 mm/hour and WBC count of 7400 cells per µL. Rheumatoid factor results were negative, and an antinuclear antibody titer was 1:320. The results from a Lyme ELISA subsequently sent from the rheumatology clinic were positive; this was confirmed by a Western blot assay (9 out of 10 and 0 out of 3 band cells of IgG and IgM, respectively). The patient was started on a 28-day course of doxycycline and his symptoms subsequently resolved. He continued to be free of further joint disease 6 months after completing treatment.

Arthritis was the first manifestation of Lyme disease described in the United States.5 Inflammation is typically confined to a single large joint, most typically the knee. Affected joints are characteristically “rheumatic,” with swelling and stiffness more prominent than the erythema, warmth, and tenderness of septic arthritis.4 A previous series comparing clinical features of Lyme arthritis to those of septic arthritis noted that of patients with Lyme arthritis (n = 55), 85% had knee involvement and 13% had hip involvement. This contrasted to those with septic arthritis (n = 45) in which 22% had knee involvement and 43% had hip involvement.6 Lyme disease involving joints other than the knee and hip occurs less commonly with ankle,7 shoulder, elbow, and wrist previously documented.4 

Lyme disease is the likely etiology of these patients’ joint disease. Two tier serological testing, as performed in these patients, has a specificity for Lyme disease that exceeds 99%.8 All of our patients had ≥9 IgG bands on Western band results. The authors of a prospective study evaluating results of Lyme Western blots reported a median of 9 IgG bands among patients with late neurologic involvement or arthritis secondary to Lyme disease. This contrasted with a median of 2 IgG bands among patients with other, unrelated illnesses, and a median of 1 IgG band among healthy subjects from endemic areas.9 The rapid response to doxycycline also suggests an infectious etiology and argues against a rheumatologic etiology for these patients’ symptoms. Staphylococcal arthritis would have presented with more overt evidence of inflammation and would likely have required intravenous therapy for septic arthritis resolution. A negative control assay performed along with ELISA and Western blots, routine in the laboratory which performed these studies, further attests to the veracity of testing. Real-time PCR assays for Borrelia from synovial fluid, done for patient 1 in this series, have a sensitivity of 85% in untreated patients10 and a specificity that approaches 100%.11 PCR assays undergo an internal control as a part of the assay. The laboratory data are therefore more suggestive of an acute presentation of Lyme disease rather than distant or convalescent infection or an unrelated infectious arthritis.

Lyme disease causing a small joint inflammation is uncommonly described. A single case of sternoclavicular arthritis secondary to Lyme disease in a patient has been reported in the literature.4 The authors of a prospective study that evaluated children (n = 44) with Lyme arthritis in an endemic area found that a minority of patients (13%) presented with a chronic pauciarticular presentation that mimicked aspects of juvenile idiopathic arthritis, and 4% had a “migratory” pattern of arthritis with multiple joints involved in a sequential pattern similar to the second and third patients described in our series.12 All of our patients were boys, which is not unusual given the epidemiology of Lyme disease in the United States. The presentation at varying times of year reflects the development of arthritis both in disseminated and chronic stages of disease.

Small joint arthritis represents a diagnostic challenge. Differential diagnoses include infectious, neoplastic, traumatic, and rheumatologic causes. A careful history and examination will often guide appropriate investigations. In endemic regions, Lyme disease should be considered in the differential of small joint arthritis. Antinuclear antibody and rheumatoid factor titers have been documented to rise in association with Borrelia infections,13 but are misleading and generally not clinically significant. Treatment guidelines for Lyme arthritis recommend 28 days of oral antimicrobial therapy and nonsteroidal anti-inflammatory agents for control of pain and swelling.14 Although amoxicillin is recommended for younger children,3 recent evidence reveals doxycycline may be safer in this younger age group than previously appreciated.15,16 

Small joint arthritis in the pediatric patient can occur secondary to a variety of disease, and carries a broad differential diagnosis. As the incidence of Lyme disease increases, clinicians practicing in endemic regions should be aware of unusual patterns of presentation. As with other manifestations of disseminated Lyme disease, serological testing in a stepwise fashion can facilitate diagnosis and antimicrobial therapy is curative.

     
  • CRP

    C-reactive protein

  •  
  • ELISA

    enzyme-linked immunosorbent assay

  •  
  • ESR

    erythrocyte sedimentation rate

  •  
  • IgG

    immunoglobulin G

  •  
  • IgM

    immunoglobulin M

  •  
  • PCR

    polymerase chain reaction

  •  
  • WBC

    white blood cell

Drs Ramgopal and Zuckerbraun drafted the initial manuscript; Drs Rosenkranz and Nowalk cared for the patients described and reviewed and revised the manuscript; and all authors approved the final manuscript as submitted.

FUNDING: No external funding.

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.