My mum has ms and doctors are starting to think she has lupus too. if this is the case how would this effect her life and can it kill her?

Complicated: Not clear why a pt who has established MS would develop lupus, as more likely she has a biologically false positive ANA titer, which can occur from some medications and even infection (syphiiis). But if she has both, treatment becomes very complex, as some rheumatological agents can worsen the MS (those that block tumor necrosis factor alpha). Unlikely to kill her, but may affect quality of life