Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted by the tick Ixodes dammini (deer tick) or a related ixodid tick.
Arthritis is the presenting manifestation in the majority of cases.
The infection is endemic in certain areas of North America and has been described in 19 countries. The disease characteristically develops in the summer and autumn-periods when the ticks are very active.
Clinical Features
The arthritis is preceded in about half the cases by a characteristic rash-erythema chronicum migrans. The appearance of the rash in striking. Half of the affected children will definitely recollect being bitten by a tick.
Prodromal systemic illness in the form of low-grade fever, stiff neck, or headache is present in about 40 percent of cases.
The arthritis is pauciarticular, usually affecting one or a few large joints.
The knee is the most common site and is involved in over 95 percent of cases. Other joints that can be affected are the elbow, hip, ankle, shoulder, sternoclavicular, and interphalangeal.
The arthritis follows the skin rash or prodromal systemic symptoms usually within a few months (Range- One week to 12 months).
The synovitis manifests itself as joint swelling, increased local heat, joint tenderness, and pain on extremes of motion. When the knee, hip, or ankle is involved, the patient is able to bear weight and walk on the affected lower limb with an antalgic limp.
The typical pattern of synovitis is brief and intermittent. If untreated, however, it becomes chronic.
Other clinical features of Lyme disease are meningitis or neurologic disease in the form of nerve palsy such as Bell’s, and cardiac involvement, particularly conduction defect.
Diagnosis
Elevated titers of I&M and I&G antibodies against Ixodes dammini will establish the diagnosis of Lyme disease.
A nonspecific finding is elevation of the erythrocyte sedimentation rate.
In its initial stages Lyme disease should be differentiated from the monarticular or pauciarticular form of juvenile rheumatoid arthritis.
This may be difficult but following differences cn help to delineate.
- The attacks of Lyme arthritis are usually brief and self-limited, but that of juvenile rheumatoid arthritis is unremitting for at least six weeks.
- Chronic iridocyclitis does not occur in Lyme arthritis.
It is advisable to carry out serologic tests to rule out Lyme disease when one is working on JRA.
Pyogenic septic arthritis is another entity to be differentiated from Lyme disease.
In bacterial arthritis, the affected joint is acutely painful, red, and hot, and the patient is unable to bear weight on the lower limbs if the knee or hip is involved. In septic arthritis, joint fluid cultures are positive in 70 percent of cases.
Synovial fluid analysis is ordinarily not of great assistance in differentiating the two because in both conditions the leukocyte count is elevated with neutrophilia. The erythrocyte sedimentation rate is elevated in both.
In case of doubt the arthritis should be treated as if septic while serologic tests for Lyme disease are sent which should be available within one to two weeks.
Treatment
Therapy consists of administration of antibiotics-penicillin or tetracycline alone.
Initially, when the arthritic symptoms are mild, penicillin may be given orally (phenoxymethyl penicillin) 50 mg/kg/day for four weeks.
If tetracycline is administered, the dosage is 30 mg/kg/day.
If the arthritis fails to respond to oral antibiotics, or if it is acute, the parenteral route is employed. Intravenous penicillin G or benzathine penicillin is given for ten days.
Antibiotics do prevent or attenuate subsequent attacks.
They should be administered for at least one month in order to minimize the risk of recurrence with exacerbation of the arthritis.
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