The influence of environmental factors related to Juvenile Dermatomyositis (JDM), its course and refractoriness to treatment.

Objective: To evaluate the influence of environmental factors and prematurity relating to juvenile dermatomyositis (JDM), its course and refractoriness to treatment.

Methods: A case-control study with 35 patients followed up at a tertiary hospital and 124 healthy controls, all residents of São Paulo. Patients were classified according to monocyclic, polycyclic or chronic disease courses and refractoriness to treatment. The daily concentrations of pollutants (inhalable particulate matter-PM₁₀, sulfur dioxide-SO₂, nitrogen dioxide-NO₂, ozone-O₃ and carbon monoxide-CO) were provided by the Environmental Company of São Paulo. Data from the population were obtained through a questionnaire.

Results: Fifteen patients had monocyclic courses, and 19 polycyclic/chronic courses. Eighteen patients were refractory to treatment. Maternal occupational exposure to inhalable agents (OR = 17.88; IC 95% 2.15-148.16, p = 0.01) and exposure to O₃ in the fifth year of life (third tertile > 86.28µg/m³; OR = 6.53, IC95% 1.60-26.77, p = 0.01) were risk factors for JDM in the multivariate logistic regression model. The presence of a factory/quarry at a distance farther than 200 meters from daycare/school (OR = 0.22; IC 95% 0.06-0.77; p = 0.02) was a protective factor in the same analysis. Prematurity, exposure to air pollutants/cigarette smoke/sources of inhalable pollutants in the mother's places of residence and work during the gestational period were not associated with JDM. Prematurity, maternal exposure to occupational pollutants during pregnancy as well as patient's exposure to ground-level pollutants up to the fifth year of life were not associated with disease course and treatment refractoriness.

Conclusion: Risk factors for JDM were maternal occupational exposure and exposure to O₃ in the fifth year of life.