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Epidemiology of juvenile arthritis in Rochester Minnesota.

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LETTERS
Epidemiology of juvenile arthritis in Rochester,
Minnesota
To the Editor:
Towner et a1 (1) recently reported higher prevalence
and incidence rates of juvenile arthritis (JA) in Rochester,
Minnesota than those previously reported. The higher incidence rate was apparently due to a higher proportion of
pauciarticular disease (74% of the total number) compared
with previous studies. The impression of the authors was
that the pauciarticular form of disease was clinically mild
with few nonarticular manifestations. For example, only 4%
of the patients had iridocyclitis.
The authors suggested that higher rates of mild
pauciarticular disease were observed because the study was
community based, whereas previous studies were university
hospital or clinic based. They speculated further that the
mild pauciarticular disease may represent 1 or more JA
subtypes with distinct etiologies.
A possible etiologic agent in at least a proportion of
the pauciarticular forms of JA in Rochester is the Lyme
disease spirochete. Patients with Lyme disease may meet
the 1977 revised American Rheumatism Association criteria
for JA (2), especially if the erythema chronicum migrans rash
doesn’t occur (as is the case in up to 25% of patients [3]) or if
it is overlooked or misidentified (4). Lyme disease is being
reported with increasing frequency in Minnesota (5,6), including in and around Olmsted County. Several patients
have had onset of the disease in the 1970s (4), overlapping
the ascertainment time of Towner’s study.
Several observations by Towner et a1 are consistent
with the possibility that Lyme disease contributes to the
increased rates of JA in Rochester. First, the frequent
pattern of pauciarthritis (including one-third of patients with
monarthritis) matches the most common pattern of arthritis
in Lyme disease (3). Second, the low incidence of eye
inflammation in this series could reflect the existence of a
form of arthritis, such as Lyme disease, not susceptible to
eye involvement. Third, 16 of 49 patients had symptom-free
intervals of at least 3 months. Attacks of arthritis in Lyme
disease are often separated by symptom-free intervals of
weeks to months (3). Fourth, the sex ratio was approximately equal (9 males and I1 females) among children whose age
at onset was between 5 and 15 and whose arthritis was of at
least 3 months duration. The ratio of males to females was
1 : I 1 when age at onset was 4. It is possible that the
inclusion of cases of Lyme disease in the older age group of
JA patients might account for the near equalization of
incidence rates among males and females.
It is unclear whether Lyme disease has emerged as a
truly new disease or has simply been recently recognized (3).
In any event, there are few cases with known onset prior to
the 1970s in Connecticut (7) or in the upper midwest (5,6,8).
It would be of interest to learn whether the incidence of
pauciarticular forms of JA in Rochester increased in the
1970s compared with the 1960s. If so, it might lend further
239
support to the notion that Lyme disease is part of the “JA”
population in Rochester and could partially account for the
unusually high rates of JA seen there.
Eric S. Schned, MD
Park Nicollet Medical Center
Minneapolis, MN
1 . Towner SR, Michet CJ Jr, O’Fallon WM, Nelson AM: The
epidemiology of juvenile arthritis in Rochester, Minnesota 19601979. Arthritis Rheum 26:1208-1213, 1983
2. Brewer EJ Jr, Bass J , Baum J , Cassidy JT, Fink C, Jacobs J ,
Hanson V , Levinson JE, Schaller J , Stillman JS: Current proposed revision of JRA criteria. Arthritis Rheum 20: 195-199, 1977
3. Steere AC, Malawista SE, Hardin JA, Ruddy S. Askenase PW,
Andiman WA: Erythema chronicum migrans and Lyme arthritis:
the enlarging clinical spectrum. Ann Intern Med 86:685-698,
1977
4. Schned ES: Lyme disease as an etiology of “unexplained”
recurrent monoarthritis. Minn Med 65:325-328, 1984
5. Williams DN, Vance JC, Hedberg C, Foley C, Osterhold M:
Lyme disease and erythema chronicum migrans in Minnesota.
Minn Med 65:217-220, 1982
6. Lyme disease: an emerging public health problem. Minnesota
Department of Health, Disease Control Newsletter 11:21-28,
1984
7. Steere AC, Malawista SE: Cases of Lyme disease in the United
States: locations correlated with distribution of Ixodes dammini.
Ann Intern Med 91:730-733, 1979
8. Dryer RF, Goellner PG, Carney AS: Lyme arthritis in Wisconsin. JAMA 241:498-499, 1979
Reply
To the Editor:
Dr. Schned raises the important issue of Lyme
disease as an etiology for some cases of pauciarticular
juvenile arthritis in endemic areas. In our study, we observed no significant difference in the overall incidence rates
of pauciarticular arthritis for the years 1960-69 versus 197079. This was also true for the specific age group 5-15 years.
Among the patients in this age group, there was a slight
preponderance of children with onset of disease between the
months of March-October, the high-risk period for Lyme
disease. Eighty-one percent of the 1960s cases and 70% of
the 1970s cases began during this &-month period. Because
the numbers are small, however, it is likely that this observation can be attributed entirely to chance. None of the
children developed neurologic or cardiac manifestations
suggestive of Lyme disease.
We would agree that Lyme disease should be seriously considered as an etiologic agent in some cmes of
juvenile arthritis in endemic areas. Seroepidemiologic studies of juvenile arthritis may eventually elucidate the magnitude of its contribution.
Clement J. Michet, MD, MPH
Mayo Clinic
Rochester, MN
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