SF writer Peter Watts needs help diagnosing mysterious, debilitating illness

Eerie. I had something similar going on in the latter part of 2014, with a very debilitating immune response that made my joints inflamed and swollen (knees, elbows, hands), among other symptoms. The pain, the pain!
The doctor sent me to a specialist, who decided to send me to more specialists to rule out Churg-Strauss syndrome. Luckily, I only fit two-thirds of the criteria. Strangely enough, after two months, it passed as quickly as it came. They never did come to a definite conclusion.