Would you expect to see severe arthralgias within the first few days of immune-therapy in a patient without history of autoimmune disease?

The short answer is: Absolutely!

The long answer is:

From a mechanistic standpoint, it is common to see severe arthralgias within days of initiating immune checkpoint inhibition, even in a patient without a prior autoimmune diagnosis.

Checkpoint inhibitors rapidly release inhibitory signals on T-cell a...

Yes, I agree with the excellent and comprehensive answer from Dr. @Dr. First Last- I’ve happened to see this strange presentation occur as well within a few days of starting immunotherapy.