3 year old Grandson - Hives, Joints inflammed, Fever

[caballus]

My 3 year old grandson came in from playing with swollen ankle, couldn't walk on it and then over the course of a couple of hours got hives all over his body. The next day the other ankle was swollen. Now, days later swelling has also gone to knees, elbows and inside of wrists. Hives still apparent. Low grade fever. One night golf-ball sized lump in middle of the back of the head then 3 more at base of skull the next morning. These have now gone away. The hives and joint swelling with debilitating pain persists after 5 days.. Drs. do not know what it is. Blood tests came back normal. Could not get urine sample - grandson will not pee in the poddy nor release urine when in hospital and catheterized. He was also receiving IV fluids at the time. After being sent home he fully released and urine was profuse. From hospital went to Pediatrician. Said they don't really know what it is -- could be one of 10 things and all but 2 of them are viral and just to let the 'bug' run its course. We're now going on 6 days and he's still miserable.

What could this possibly be? Very worried.

[caballus]

Thanks ... has been back to Dr.(s) ...  Daughter has gotten 4 opinions. All conflicting and no one knows. Last Dx was "Serum Sickness" but he hasn't had immunizations or medications for a long while. Yesterday the rash was covering his belly and face. Swelling still appararent in all joints. Fever still running low. No other symptoms. :(

[sweetpea03]

Sounds like an allergic reaction.. though that's just one possibility. Did they try testing his uric acid levels?, as it could be gout. It could also be an infection, so it's just a matter of time. Have you gone for a second opinion? I'd go to another doctor to see what they say. good luck.