I am seronegative MG as well. I understand her and yours sadness and frustration with the limited options of treatment for SNMG. It is a challenge finding the right MG treatment cocktail available for SNMG patients .
The response to different MG treatments is variable, not everyone responds to one treatment and others do well. The hard and uncomfortable part to understand is that most of the MG treatments ( except prednisone and IVIG ) , take time to work. It is not a quick fix and months need to go by to see if the MG treatment used is the right one for her. (Her NEURO doc will explain further the ups and downs of each MG treatment option) So you suffer much at the beginning waiting for a good response later or if no response a change to another treatment option or another med is added to your regimen. The kicker is being vigilant for the side effects , managing those which are acceptable and coping as best as you can. ( Having access to a Pharm D provider helps)
My NEUROMuscular doc has prescribed RITUXIMAB IV infusion
which I will start soon. Perhaps this may be another treatment option for her.
Tried IVIG once and had impressive improvement which lasted around 4 weeks. The dosing amount received is important for a good response . I believe IVIG works for awhile then after many treatments not so much.
Emotional distress , other illnesses, worry & despair can trigger MG flares and symptoms worsen . The fear of the unknown can be scary and emotionally paralyzing.
As an autoimmune SNOWFLAKE disease the MG symptoms fluctuate weirdly and are unpredictable which is a part of the MG life we have to accept and become ZEN with our illness (LOL!) . Ultimately , a life altering moment can occur , to reach a decision to be mindful, to make a choice to just live the best MG life possible despite all the crazy limiting MG symptoms .
As for VyVGart , my NEURO doc stated studies are currently evaluating using this treatment for SNMG and have shown promising results, hopefully when FDA approval . it will be a standard option for us SNMG folks soon.
As always, sometimes a second opinion with a NEUROMUSCULAR doc may be helpful, another pair of eyes to confirm & evaluate her diagnosis, and provide a treatment plan.
Consider having your sister see a psychologist counselor for talk therapy which may benefit her to discuss her emotions , the shock off this diagnosis , the grief , despair , being scared of worsening symptoms all the time , flight or fright feelings and accepting her lifestyle changes adjustment, once her MG is controlled, relief . She should have a discussion and review of life tools to help her adjust to this devastating change of life event looking forward to a remission status.
She is blessed to have your support during this health journey crises challenge.
Have FAITH and be hopeful.