Background Several publications have demonstrated that the most frequent mutation in Paget's disease of bone (PDB), SQSTM1/P392L, leads to some of the phenotypic characteristics of PDB, but this single mutation is seemingly unable to result in the complete pagetic phenotype, suggesting that other mechanisms such as environmental factors may play a role.
Objectives Identify environmental factors associated with PDB or with the SQSTM1/P392L mutation carriage in the French-Canadian population.
Methods We investigated environmental factors through a questionnaire in 176 French-Canadian patients with PDB and 147 healthy controls not carrier of the SQSTM1/P392L mutation. The questionnaire contained the following sections: socio-demographic and physical characteristics, tobacco exposure, diet, residency, work, leisure, and contact with animals, during childhood/adolescence and adulthood. Associations between environmental factors and PDB, or SQSTM1/P392L mutation (86 individuals carried the mutation, including 48 patients with PDB), were searched relying on Chi-squared, Fisher and t tests. Odds ratio (OR) and 95% confidence interval were calculated. Univariate followed by multivariate analysis were done for association with PDB. Correlation between members of same family was considered when possible. Analysis adjusted for age and gender were done for the association study with SQSTM1/P392L mutation.
Results We administered the questionnaire to 361 participants: 176 patients with PDB and 147 healthy controls. 86 individuals were carriers of the SQSTM1/P392L mutation, among whom 48 were patients with PDB and 38 were healthy carriers of the mutation. In univariate model, we found an association of PDB with, wood-fire heating in childhood (OR=2.48 (1.37-4.49), p<0.01), rural residency during adolescence (OR=2.09 [1.19-3.67], p<0.01) and residency near a farm in childhood (OR=1.77 [1.02-3.09], p=0.04). In multivariate model, significant association was found between PDB and wood-fire heating in childhood (OR=2.10[1.13-3.90], p=0.02). Male gender (OR=4.63 [2.46-8.72], p<0.01) and lower educational level (OR=2.13 [1.13-4.02], p=0.02) were also associated with PDB. Carriage of the SQSTM1/P392L mutation was associated with rural residency (OR=2.66 [1.42-4.99], p<0.01), wood-fire heating (OR=2.25 [1.20-4.24], p=0.01), residency near a farm (OR=2.37 [1.29-4.38], p<0.01) and work on a farm (OR=3.30 [1.75-6.24], p<0.01) in childhood. There was also an association with residency near a mine (OR=6.64 [1.68-26.27], p<0.01) and work in a mine (OR=6.89 [1.35-35.31], p=0.02). Interestingly, association with exposition to different animals during childhood were found with the SQSTM1/P392L mutation (p<0.05): horse, dog, sheep, pork, cattle and poultry.
Conclusions PDB and the carriage of the SQSTM1/P392L mutation were significantly associated with rural residency. Carriage of the SQSTM1/P392L mutation was also strongly associated to work on a farm or in a mine and exposition to some animals during childhood.
Acknowledgements CHU de Quebec foundation
Disclosure of Interest None declared