Sophia
I can understand the pain and anxiety that you are going through because I've been going through this situation for two years now. I have a daily fever - not as high as your son's however - of up to 101F which is accompanied by arthralgia, fatigue, appetite and weight loss. I've been hospitalised 4 times and subjected to numerous and painful tests which all came out negative. So, now doctors have come to the conclusion that it all boils down to a connective tissue disease - possibly lupus. My advice would be, since the doctors who are monitoring your son have excluded any "bad" diseases, to look even for something "unimportant" like a bad tooth or toncils which are "hidden". If you've excluded those possibilities too, you should run some rheumatological tests on your son like ANA, anti-dsDNA, C3 and C4 levels, RF-factor, LE cells etc. If any of those is at least indicatory of a connective tissue disease the best you can do is wait. It'll come up in the bloodwork some time. Of course, some tests like CAT-scans, a mantoux test and a full immunological set of tests are necessary, especially those looking for EBV-virus, a mono-test, toxoplasmosis, IGg and IGm, typhoid tests and specifically Widal and Wright tests. It could be brucellosis. As you can see, there are so many possible causes of unexplained fever that doctors are at a loss sometimes. 8 - 13% FUO (fever of unknown origin) cases worldwide elude diagnosis. I know how difficult this is but you have to be patient and be on alert at any time! Don't just accept a FUO "diagnosis", get a 2nd and 3rd - if necessary - opinion. At least, one that is somehow satisfactory. And... don't give up! Hope dies last! I hope I have helped you at least a little bit! Hang in there!