Environmental factors preceding illness onset differ in phenotypes of the juvenile idiopathic inflammatory myopathies.
OBJECTIVE
To assess whether certain environmental factors temporally associated with the onset of juvenile idiopathic inflammatory myopathies (JIIMs) differ between phenotypes.


METHODS
Physicians completed questionnaires regarding documented infections, medications, immunizations and an open-ended question about other noted exposures within 6 months before illness onset for 285 patients with probable or definite JIIM. Medical records were reviewed for 81% of the patients. Phenotypes were defined by standard clinical and laboratory measures.


RESULTS
Sixty per cent of JIIM patients had a reported exposure within 6 months before illness onset. Most patients (62%) had one recorded exposure, 26% had two and 12% had three to five exposures. Patients older than the median age at diagnosis, those with a longer delay to diagnosis and those with anti-signal recognition particle autoantibodies had a higher frequency of documented exposures [odds ratios (ORs) 95% CI 3.4, 31]. Infections were the most common exposure and represented 44% of the total number of reported exposures. Non-infectious exposures included medications (18%), immunizations (11%), stressful life events (11%) and unusual sun exposure (7%). Exposures varied by age at diagnosis, race, disease course and the presence of certain myositis autoantibodies.


CONCLUSIONS
The JIIMs may be related to multiple exposures and these appear to vary among phenotypes.
Rider
Lisa G
LG
Environmental Autoimmunity Group, National Institute of Environmental Sciences, National Institutes of Health, DHHS, Clinical Research Center Room 4-2352, 10 Center Drive, MSC 1301, Bethesda, MD 20892-1301, USA. riderl@mail.nih.gov
Wu
Lan
L
Mamyrova
Gulnara
G
Targoff
Ira N
IN
Miller
Frederick W
FW
D017668:Age of Onset; D001323:Autoantibodies / Q000235:genetics*; D002675:Child, Preschool; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D008297:Male; D009220:Myositis / Q000175:diagnosis*; D010641:Phenotype; D012307:Risk Factors; D013997:Time Factors
D001323:Autoantibodies
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