>>4430465Mouse has CVID, an inherited genetic condition where her immune system is SHIT. She receives regular plasma donation transfusions to take advantage of the antibodies it contains. This allows her to fight off common infections from everyday life.
She led a relatively normal life doing this, until she got hit HARD by a lung infection. It damaged much of her lung function, and her physical inactivity during her recovery led to muscle atrophy. This is why she's bedridden and weak.
As for her eating issues, CVID usually causes issues with digestion.