Study of Systemic Lupus Erythematosus

* INCLUSION CRITERIA: Patients with known or suspected SLE will be evaluated in either the outpatient or inpatient research ward of the Clinical Center as indicated. Patients will not be selected based on age, race or gender. However, due to the nature of the disease, the patient population will not be expected to be evenly distributed, since SLE is predominantly a disease of young females, with increased prevalence in select racial groups, particularly African Americans and Hispanics. First and second-degree relatives of the patient may be recruited in the study for genetic analysis. We will ask for the patient s permission to contact his/her relatives. * SLE or suspected SLE established by ACR/EULAR or ACR criteria * Ability to give informed consent * Adult and minor relatives (first and second degree) of individuals Included in IV-G (only for genetic studies) * Ability of the patient or minor relative s parents to give informed consent * Affected individuals age \>= 3 years with no upper age limit * Healthy Volunteers (non-related) age \>=18 with no upper age limit * Healthy Volunteers (first- and second-degree relatives) age \>=3 with no upper age limit * Vascular studies adults only age \>=18 with no upper age limit EXCLUSION CRITERIA: * Concomitant medical problems which would confound the interpretation of studies gathered by this protocol. Included in this is the presence of HIV in the blood, active malignancies, or other significant medical conditions that may interferes with interpretation of some lupus studies. * Concomitant medical, surgical or other conditions for which inadequate facilities are available to support their care at NIH * Inability or unwillingness to comply with follow up requirements (e.g. distance, social, physical limitations) * Any comorbidity of medical or psychological/psychiatric condition or treatment after reviewing of patients previous or outside medical records, that in the opinion of the Principal Investigator, would exclude the subjects from the research studies (e.g. Patient requiring urgent and/or acute medical care, surgical or other procedures) * Unwilling to participate in research studies or to provide research samples or data * Any concomitant medical problems or are taking medications which would confound the interpretation of studies they are considered for EXCLUSION CRITERIA FOR VASCULAR STUDIES ONLY, FOR SLE AND HEALTHY CONTROLS: * Subjects with a contraindication to MRI scanning will not receive the optional Cardiovascular MRI. These contraindications include subjects with the following devices: * Central nervous system aneurysm clips unless it is labeled safe or conditional for MRI * Implanted neural stimulator (e.g.TENS-Unit) unless it is labeled safe or conditional for MRI * Implanted cardiac pacemaker or defibrillator unless it is labeled safe or conditional for MRI * Cochlear or any type of ear implant unless it is labeled safe or conditional for MRI * Ocular foreign body (e.g. metal shavings) * Implanted Insulin pump or drug infusion device unless it is labeled safe or conditional for MRI * Metal shrapnel or bullet unless cleared by plain x-ray as safe for MRI * Subjects with renal excretory dysfunction, estimated glomerular filtration rate \< 60 mL/min/1.73m\^2 using the CKD-EPI equation or equivalent (using the CRIS-calculated eGFR to define the threshold) and a serum creatinine measured within 2 weeks without intercurrent change in medical condition or medications. Subjects meeting this exclusion criterion may still be included in the study but will not be exposed to the cardiac CT angiography, or gadolinium-based contrast agents. * Pregnant or lactating women will be excluded from vascular studies. * Any clinical instability precluding subject from getting MRI as determined by the enrolling clinician. * Healthy controls with known history of coronary artery disease, peripheral vascular disease or atherosclerosis. * Individuals younger than 18 years old will be excluded given the radiation exposure as well as the lack of proper validation for the proposed vascular function studies.