Blood samples shed light on mysterious muscle disease

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Diagnosed with MG based on clinical presentation and seropositivity for MG associated autoantibodies (AChR binding, MuSK, or LRP4 antibodies), and/or a decremental response on repetitive nerve stimulation, positive single fiber electromyography (EMG) or positive edrophonium test. Signs and symptoms should not be better explained by another disease process. * A) Diagnosed with MG within 2 years of study enrollment and with adequate records to document MG history (e.g., onset, MG meds) prior to enrollment at the discretion of the investigator. or B) MuSK antibody, LRP4 antibody, or thymoma-associated MG at any point in the disease course. Patients with a diagnosis of MG more than 2 years prior to the first study visit who are expected to undergo a thymectomy may also be enrolled. * Participant has the capacity to understand and sign a written informed consent form. * Participant must be willing to complete the study and return for follow-up visits. Exclusion Criteria: * A history of chronic degenerative, psychiatric, or neurologic disorder other than MG that can produce weakness or fatigue that would confound outcome measure assessments or any disorder that interferes with participation in this protocol. * Participant is unable or unwilling to comply with the study procedures. * Treatment with any investigational agent within 4 weeks of the baseline visit or 5 half-lives of the investigational drug (whichever is longer). 1. Participation in other observational studies is not exclusionary 2. It is anticipated that some participants enrolled in EXPLORE-MG2 may be enrolled in future interventional trials while active in EXPLORE-MG2. This is acceptable. The exclusion only applies to starting EXPLORE-MG2 when participation in an interventional trial is imminent or active. 3. If an EXPLORE-MG2 participant is later enrolled in an interventional trial, it will be at the investigator's discretion whether to continue collecting biosamples while the patient is participating in the interventional trial. Collection of natural history data should continue. * Known active malignancy at enrollment other than skin cancer, low grade prostate cancer, or cervical cancer in situ. Thymoma is not included in this exclusion criteria. * Any other disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates or that may affect the interpretation of the results or render the participant not an appropriate study participant.