Children with systemic lupus erythematosus can have neurologic and cognitive complications from their disease, called neuropsychiatric lupus (NPSLE). It is important to identify and address these complications early to improve care for these children. We have studied two blood markers of brain injury called neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) in prior studies. These markers showed potential utility in identifying significant neurologic complications and cognitive difficulties. However, we still need to evaluate the factors that may influence these marker levels to be able to use them in clinical practice. In this proposal, we will collect two blood samples 12 months apart from 38 participants enrolled into the CARRA Lupus Registry with a history of NPSLE. We will test both NfL and GFAP in the blood for each participant. We will combine this data with that from other studies of the PIs on SLE in children. 1) We will evaluate differences in these markers of brain injury in children with a history of NPSLE, children with SLE alone, and children without SLE. 2) We will then look at the factors that influence these levels in children with SLE alone, and in NPSLE specifically. This study will help us determine the utility of these markers for use in clinical practice for children with lupus, lay the foundation for future longitudinal studies of these markers, and will advance the CARRA mission by supporting the development of evidence-based care for children with neurologic complications of lupus. Additionally, this focused collection of samples from a population of children with lupus with detailed neurologic data is critical for future studies developing novel biomarkers of neurologic disease, to improve care for children who experience NPSLE or to help prevent it.