The overarching goal of this study is the development of a physiologic endpoint of pain and treatment effect in three distinct rheumatology populations. This would enable objective assessment of pain and treatment in these populations and enable a much more precise approach to treatment. Such an endpoint stands to significantly improve outcomes in these patients by eliminating the need for a trial-and-error approach to treatment. This is a single site observational study that aims to collect initial pilot data in three distinct patient groups. As this is observational, there is no randomization or blinding in the study. Patients will be followed for a period of one year after enrollment. Baseline measurements will be taken at the time of enrollment, and at each subsequent standard of care clinic visit as feasible, for a period of one year. As this is an observational study, there will be no change to the treatment for any patient due to research activities. The primary objective of this study is the characterization of the nociceptive index in three pediatric rheumatology populations. The secondary objective is the characterization of the nociceptive index in these populations in response to standard of care interventions. This is necessary to demonstrate the ability of this approach to serve as an endpoint of treatment effect.