VAIL, COLO. – Arthritis is far and away the most common manifestation of late Lyme disease, affecting up to 30% of children whose early-stage disease went untreated.
Lyme arthritis presents with a distinctive clinical picture. Nevertheless, this common condition is often initially mismanaged as a joint sprain or other orthopedic injury, with the correct diagnosis coming only following referral after a month or more with no improvement, according to Dr. Roberta L. DeBiasi, acting chief of the division of pediatric infectious diseases at Children’s National Medical Center, Washington.
Dr. Roberta L. DeBiasi
"We see tons of kids with Lyme arthritis. We get two or three cases every week in our clinic," she said at the conference.
Lyme arthritis occurs months to years after an untreated exposure to Borrelia burgdorferi. Affected patients typically present with a history of recurrent, weeks- or months-long attacks of joint swelling in one or a few joints. The knee is by far the most common site, but other large joints can be involved, as can the temporomandibular joint. An involved knee may swell up to literally the size of a basketball, yet the child has no fever, erythema, or systemic complaints, and surprisingly little pain given the effusion size.
Chronic progressive arthritis that’s not preceded by brief waxing and waning attacks doesn’t fulfil the criteria for Lyme arthritis. Neither does chronic symmetric polyarthritis, Dr. DeBiasi stressed.
Patients with suspected Lyme arthritis typically undergo arthrocentesis because there are other possible explanations for reactive arthritis besides Lyme disease. The synovial fluid in a patient with Lyme arthritis shows prominent neutrophils, mild to moderate inflammation, and a median WBC of 25,000/mm3. But diagnostic confirmation of Lyme arthritis requires serologic testing, which will invariably be enzyme immunoassay-positive, IgG-positive on the Western blot test, and IgM-negative on the Western blot because arthritis is a late manifestation of infection. Dr. DeBiasi doesn’t consider synovial fluid PCR a useful adjunctive diagnostic test.
The first-line treatment recommended in the Infectious Diseases Society of America guidelines (Clin. Infect. Dis. 2006;43:1089-134) is 28 days of oral therapy with doxycycline at 4 mg/kg per day divided b.i.d., to a maximum of 100 mg b.i.d.; amoxicillin at 50 mg/kg per day divided t.i.d., to a maximum of 500 mg t.i.d.; or cefuroxime axetil at 30 mg/kg per day divided b.i.d., to a maximum of 500 mg b.i.d. Unlike in late central nervous system Lyme disease, which responds swiftly to treatment, expect slow resolution of the joint inflammation.
"This is a situation in which you can avoid giving someone a PICC line. Patients do great with oral therapy. You just need to do it for quite a while. The joint may show no change after the first week of therapy and may be only slightly smaller after 2 weeks. I give anti-inflammatory drugs concurrently to speed improvement in swelling and range of motion," Dr. DeBiasi explained.
If, however, joint swelling persists at the end of 28 days of oral therapy, two options are available. Both involve a 1-month wait off treatment before considering retreatment.
The first option, which is preferred if the patient’s joint swelling is substantially improved but not completely resolved, is another 28-day course of oral antibiotic therapy.
The alternative is to initiate 2-4 weeks of intravenous ceftriaxone at 50-75 mg/kg per day in a single dose, to a maximum of 2 g. This is the favored option when a patient has shown no improvement at all or is worse after the first course of oral therapy.
"That’s happened once in the 6 years I’ve been taking care of kids with Lyme arthritis. The vast majority do well with oral therapy," she said.
Dr. DeBiasi reported having no financial conflicts.