Patient description: The patient is a 16-year-old girl recently diagnosed with myasthenia gravis, class IIa. She complains of diplopia and weakness affecting in her upper extremities. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She is on acetylcholinesterase inhibitor treatment combined with immunosuppressants. But she still has some symptoms. She does not smoke or use illicit drugs. She is not sexually active, and her menses are regular. Her physical exam and lab studies are not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 15.0-999.0,  Systemic Autoimmune Diseases In order to be eligible to participate in this study, an individual must meet all of the following as per respective group: 1. Stated willingness to comply with all study procedures and availability for the duration of the study 2. Male or female age greater than or equal to 15 years old with no upper age limit. 3. Ability of subject to understand and the willingness to sign a written informed consent and/or assent document. 4. For Healthy Volunteers Group Age greater than or equal to 15 with no upper age limit No history of autoimmune diseases and in good general health as evidenced by medical history. 5. For symptomatic COVID-19 group must have laboratory evidence (positive PCR for or other test developed after this proposal gets approved and is available through the Clinical Center) and one of the signs and symptoms associated with COVID-19 infection (e.g. fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, diarrhea). 6. For post COVID-19 study visits must have laboratory evidence (e.g. positive PCR for SARS COV-2, antibody against SARS-COV-2 or other test developed after this proposal gets approved) of current or prior exposure to COVID-19. Alternatively, patients should have documented evidence of having received one of the SARS-COV-2 vaccines that may become available during the study. 7. For subjects with known COVID exposure, they must fulfill one of the following A minimum of 28 days has passed since the initial positive test date AND B. Resolution of fever was greater than or equal to7 days ago (without the use of fever-reducing medications) AND C. Resolution of respiratory symptoms was greater than or equal to7 days ago, OR A minimum of 10 days has passed since the initial positive test AND B. A minimum of 2 consecutive oropharyngeal swabs OR 2 consecutive nasopharyngeal swabs or 2 saliva testing collected greater than or equal to 24 hours apart that are negative for SARS CoV-2 PCR A positive PCR requires restarting the series of swabs (wait 5 days to retest) 8. Specific for Systemic Autoimmunity Diseases Group Age greater than or equal to 15 years with no upper age limit Systemic lupus erythematosus (SLE): Meets at least 4 of 11 modified American College of Rheumatology (ACR) (1997) Revised for the Classification of Systemic Lupus Erythematosus or Systemic Lupus International Collaborating Clinics (SLICC) classification for systemic lupus erythematosus Anti-neutrophil cytoplasmic antibody associated vasculitis (AAV): Meet Revised 1990 ACR for Granulomatosis with polyangiitis (GPA) or the 2012 Chapel Hill Nomenclature for microscopic polyangiitis (MPA) Idiopathic inflammatory myopathies (IIM):Meets the 2017 EULAR/ACR Classification for Adult and Juvenile idiopathic inflammatory myopathies and their major subgroups  An individual who meets any of the following will be excluded from participation in this study: 1. Pregnant and lactating subjects will be excluded because pregnancy and lactation modify immune responses and may interfere with correlations. 2. 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 studies. 3. Concomitant medical, surgical or other conditions for which inadequate facilities are available to support their care at NIH. 4. Inability or unwillingness to comply with follow up requirements (e.g. distance, social, physical limitations). 5. Any comorbidity of medical or psychological/psychiatric condition or treatment, that in the opinion of the Principal Investigator, would the subjects from the research studies (e.g. Patient requiring urgent and/or acute medical care, surgical or other procedures) 6. Unwilling to participate in research studies or to provide research samples or data 7 for the (optional) vascular studies: -Healthy volunteers with known history of coronary artery disease, peripheral vascular disease or atherosclerosis. 8 for the (optional) scan: -Individuals younger than 18 years old will be excluded given the radiation exposure 9. Subjects with SAD and Healthy volunteers younger than 18 years old will be excluded from chest x-rays unless clinically indicated