Study of Families With Twins or Siblings Discordant for Rheumatic Disorders

This study will examine families in which one sibling of a sibling pair, or twin pair, has developed a systemic rheumatic disease and one has not, to see if and how the two differ in the following: * Blood cell metabolism; * Types of cells in the blood; * Environmental exposures or genetic factors that might explain why one developed disease and the other did not. Families in which one sibling has developed a systemic rheumatic disease, rheumatoid arthritis, systemic lupus erythematosus, scleroderma, dermatomyositis, or myositis, and the other has not, are eligible for this study. The siblings may or may not be twins, but must be of the same gender and be within a 5-year age difference. Biological parents, or, in some cases, children, will also be included in the study. Normal, healthy volunteers will serve as control subjects. Participants will undergo some or all of the following tests and procedures: * Medical history and physical examination. Participants will also be asked permission to obtain medical records for review. * Questionnaires about environmental exposures at work, at home, and elsewhere. Probands (participants with rheumatic disease) and their healthy siblings will also answer questions about infections, vaccinations, medications or dietary supplements, sun exposure, and stressful events during the year before disease diagnosis in the affected sibling. * Blood and urine collection for the following tests: * Routine blood chemistries and other studies to rule out certain diseases or medical problems; * Evidence of past toxic exposures and certain infections; * Presence of cells from the mother in the child s blood and vice versa. (Recent studies suggest that during pregnancy or delivery, cells from the mother and baby may be exchanged and circulate in the body for many years, possibly causing problems); * In twin or sibling pairs, presence of certain genes that may be more common in patients with systematic rheumatic diseases as compared with their unaffected siblings and normal volunteers; * In identical twins, comparison of their blood cell metabolism to see if and how the metabolism differs in people with rheumatic disease. Participants may be asked for permission to have some of their blood and urine samples stored and to obtain previously collected blood or tissue biopsy specimens that are no longer needed for clinical care, for research purposes. They may also be asked to give additional blood or urine samples. Participants will be followed every year for 5 years (either in person or by questionnaire) to evaluate any changes in their condition. The final 5-year evaluation will repeat some of the questionnaires and procedures described above.