Infections were the most common type of exposure identified within 6 months before diagnosis, consisting of 45% of the total number of reported exposures, followed by medications (18%) and immunizations (11%) ( Table 2 ). Patients 47.5 years of age at onset, those with 44 months delay to diagnosis, those with a polycyclic illness course and those who were myositis autoantibody negative were more likely to have an infection in the 6 months before diagnosis than older patients, those with greater delay to diagnosis, those with a monocyclic or chronic continuous illness course or those who had anti-p155 or anti-SRP autoantibodies (ORs 1.8-4.3, Table 2 and data not shown). There were no other differences between documented types of exposure between clinical or other autoantibody phenotypes, nor by gender, disease course, race or delay to diagnosis.