I am so sorry to hear your daughter is experiencing pain and muscle weakness. It can be so challenging when new aches and pains arise and you're trying to figure out what exactly is going on. People who are seronegative are sometimes thought to have milder symptoms of RA, but that’s not always the case. The condition affects everyone differently, and symptoms can change over time. The only way to know what's going on is by being seen by a doctor. And while this is the obvious thing to do, it can still be hard to pinpoint why the new aches and pains are occurring. But to still give some content to your question, RA can impact the muscles and connective tissues. If you're seronegative but have RA symptoms, you could have another condition. So weeding any other possibilities will be key here. Hoping you and your daughter get some answers soon. Warmly, Latoya (Team Member)