Evaluate the Benefit of Corticoid Sparing in Elderly With Generalized AntiRAch Myasthenia Gravis Treated With IV or SC Efgartigimod

Inclusion Criteria:

* Male or female subjects aged ≥65 years
* Diagnosed with gMG with confirmed documentation and supported by a physical exam and confirmed seropositivity for AChR-Abs.
* Meets the clinical criteria as defined by the Myasthenia Gravis Foundation of America (MFGA) for generalized MG class IIa, Iib, IIIa, IIIb.
* Patient suitable for efgartigimod treatment
* MG-ADL score ≥ 2
* Treated with high (\>50mg/daily) or intermediate (20-50mg/daily) dose of oral corticosteroids (prednisone or prednisolone) and in stable dose of concomitant treatments for at least three months (changes of anticholinesterase therapy are permitted).
* Patient that has developed at least one of the following iatrogenic comorbidities after the introduction of intermediate or high dose of oral corticosteroids: type 2 diabetes; arterial hypertension; overweight; sleep disorders; irritability and/or Patient experiencing a documented worsening of at least one of the following comorbidities after the introduction of intermediate or high dose of corticosteroids, including type 2 diabetes; arterial hypertension; overweight; sleep disorders; irritability
* Capable of understanding the written informed consent, and providing signed, dated, and witnessed written informed consent
* Willing and able to comply with scheduled visits, treatment plan, study restrictions, laboratory tests, contraceptive guidelines, and other study procedures
* Patient affiliated to a European social security system

Exclusion Criteria:

* Any current mental condition (psychiatric disorder, senility, or dementia) that, in the opinion of the investigator, may affect study compliance or prevent understanding of the aims, investigational procedures, or possible consequences of the study; and/or patient with a Mini-mental State Examination (MMSE) \<28.
* History of any illness or any clinical condition that, in the opinion of the investigator, might confound the results of the study or pose an additional risk in administering study drug to the subject.
* Ongoing malignancy including solid tumors, hematologic malignancies and in situ carcinoma (except basal cell and squamous cell carcinomas of the skin, or in situ carcinoma of the cervix uteri that have been completely excised and cured)
* Clinically significant uncontrolled active or chronic bacterial, viral, or fungal infection at screening
* Vaccination with live or live-attenuated vaccines within the 6 weeks
* Patient already treated with anti-complement (wash-out period 3 months) or anti-FcRN (wash-out period 3 months), anti-CD20 (wash-out period 6 months) and PLEX (wash-out period 1 month)
* Patient with end-stage disease or with a disease that will enable him to be evaluated and/or treated
* Patient protected by law, under guardianship or curator ship, or not able to participate in a clinical study according to the article L.1121-16 of the French Public Health Code.