Environmental Risk Factors of Pediatric Onset Primary Sclerosing Cholangitis and Autoimmune Hepatitis

OBJECTIVES: The aim of this population-based observational case-control questionnaire study was to investigate the possible role of environmental risk factors associated with pediatric onset autoimmune liver diseases.
METHODS: Seventy-one patients with autoimmune liver diseases (< 16 years) received a questionnaire with 22 items, evaluating contact with environmental factors (e.g., family manners, type of housing, pets) before the diagnosis. Two age and sex matched control groups were used: 1) inflammatory bowel disease (IBD; n = 91) and 2) healthy subjects (n = 716; matched also for place of residence at birth). Univariate analysis (OR and 95%CI) for all variables was calculated. Fisher's exact test was performed to depict associations between variables and the multivariate logistic regression to test their interactions.
RESULTS: In the final analyses, the responses of 51 autoimmune liver diseases cases (n = 51/71; 72%), 59 IBD controls (n = 59/91; 65%), and 292 healthy controls (n = 292/716; 41%) were investigated. In univariate analysis only: 1) having a cat, 2) having a dog and 3) having a cat or a dog were risk factors of autoimmune liver diseases (OR varying between 2.6-3.4); no other significant associations (e.g., place of residence, number of siblings, family manners) were found. Multivariate logistic regression analyses showed that especially living with a cat in block of flats was a risk factor (OR: 3.6; 1.2-10.8).
CONCLUSIONS: Living in a close contact with a pet (especially a cat) was a risk factor of autoimmune liver diseases. This finding may suggest an involvement of an unidentified agent (i.e., toxin/microbe) among the triggers of these diseases.