Natural History, Genetics, and Pathophysiology of Systemic Juvenile Idiopathic Arthritis, Adult-Onset Still's Disease, and Related Conditions

* INCLUSION CRITERIA:

Affected subject:

* Patients with signs and symptoms of sJIA will be classified as outlined in Diagnosis/Classification Criteria.

  1. Patients less than 16 years of age will be considered to have sJIA if they meet the ILAR criteria for sJIA.
  2. Patients 16 years of age and older will be considered to have sJIA if they have previously met ILAR criteria for sJIA.
* Patients with signs and symptoms of AOSD will be classified as outlined in Yamaguchi Criteria for diagnosing Adult-Onset Still's Disease.

  1. Patients 16 years of age and older will be considered to have AOSD if they meet the Yamaguchi criteria for AOSD (including a negative ANA and RF).
  2. Patients may be considered to have a diagnosis of AOSD if they met criteria for diagnosis in the past but do not still have present evidence of disease.
  3. Pregnant people with still's disease are allowed to enroll. Pregnant people will not be asked to submit to a skin biopsy or bone marrow aspiration.
* The minimum age for participation in this study is between 0 and older.

Healthy Subjects:

1. Healthy Volunteers related to individuals included under items 1 and 2 above will be enrolled.
2. Unrelated healthy volunteers will be enrolled for clinical, cellular, molecular, and biochemical assays, and genetic evaluation. Individuals who undergo phlebotomy specifically to provide a control specimen will include both pediatric and adult patients and will not be pregnant.
3. Healthy Volunteer should not have any history of autoimmune, autoinflammatory, rheumatic or proliferative/malignant disease or any unexplained inflammatory signs/symptoms or conditions (applies to unrelated).

   * The minimum age for participation in this study under this cohort is 2 years.

EXCLUSION CRITERIA:

Affected and Healthy subjects:

1. In adults, inability, or the lack of capacity to provide informed consent. In the case of minors, unavailability of a parent or guardian.
2. Presence of any medical condition that would, in the opinion of the investigators, confuse the interpretation of the study.
3. Unavailability, or inability to adhere with the schedule for follow-up visits