Eligibility Criteria

• Adults or children who have been diagnosed with polymyositis or dermatomyositis within the last two years.
• Healthy friends or cousins of individuals with polymyositis or dermatomyositis.

The inclusion criteria for enrollment of myositis subjects are:

• Diagnosis of myositis based on criteria for possible, probable or definite PM or DM, with or without other connective tissue diseases, documented within 24 months of enrollment (using the most recent diagnosis date to define the 24 month period).
• CXR to assess possible ILD and assign the subject to the presumptive anti-synthetase positive or negative category if clinically indicated.
• Able and willing to give informed consent, to complete the questionnaires and to donate blood samples (in case of children grester than 2 years of age but <18 years of age , parent/legal guardian must be willing and able to provide informed consent and child must provide assent).

The inclusion criteria for controls are:

• Friends or, if friends are not available, cousins of the anti-synthetase positive myositis patient, or, if friends or cousins are not available, volunteers from the general community (such as the NIH Normal volunteer program), sex- and age- (within 5 years for minors and within 10 years for adults) matched, who is living as close as possible to the geographic area of the myositis patient.
• Controls should be without a recognized autoimmune disease or ILD.
• Able and willing to give informed consent, to complete the questionnaires and to donate blood samples (in case of children greater than 2 years of age but <18 years of age, parent/legal guardian must be willing and able to provide informed consent) and child will provide assent according to child maturity level and understanding).