Call your MS doctor for advice.
Could be a side effect of tecfidera.

“Twelve of the 14 were women (mean age 42) and, in 50 percent of these cases, liver injury began within one month of treatment start. The severity of injury was moderate or moderate-severe in eight patients and mild in six, but none went into liver failure or needed an organ transplant. Tecfidera use was halted for all these patients, and blood levels of liver injury markers returned or trended to normal after 14 days, as is typical in drug discontinuation.”

“Time on Tecfidera when people have Enlarged spleen *:

< 1 month: 40 %
1 - 6 months: 40 %
6 - 12 months: 0.0 %
1 - 2 years: 0.0 %
2 - 5 years: 20 %
5 - 10 years: 0.0 %
10+ years: 0.0 %”

“The spleen sits under your rib cage in the upper left part of your abdomen toward your back. ... An enlarged spleen is not always a sign of a problem. ... An enlarged spleen can be caused by infections, cirrhosis and other liver diseases, blood diseases characterized by abnormal blood “

I JUST experienced the very same thing a couple nights ago, a stabbing pain in my left rib area, almost took my breath away.... but it went away after a few minutes. Weirdest thing, and I forgot asn't til I just read this.. I'm on copaxone, but I am doing steroid infusion right now for other new symptoms

@Tecfidera and @aubagio require close monitoring of liver. On @aubagio the liver is checked via blood test every month for the first 6 months. I wonder how doctors test to see if liver or spleen is enlarged. From what I gather a liver problem can affect the spleen. I’m on @aubagio and haven’t gotten the required blood test, so will do that as soon as I get my insurance restarted. So far no liver or spleen location pain, but keeping a close watch for any changes in those areas.

Good luck with your insurance.

The aubagio safety guide states to get blood test for liver once per month for the first 6 months. I double checked and it does not state how often to check after the end of the first 6 months. I suspect getting checked depends on whether or not something changes. Pain at spleen area should be checked out and a second opinion, for sanities sake, then why not, it’s your body.
Maybe they press on the liver/spleen areas to determine if enlarged. And also blood test.