Do you discontinue or adjust azathioprine when a patient develops elevated MCV after starting it?

Great question, with practical implications for the clinic:

Azathioprine (AZA) is a prodrug that likely exerts its immunosuppressive effects against B- and T-cell function by interfering with purine metabolism through its metabolites (including 6-MP).

Logically, many of the "classic" AZA side effect...

Interesting discussion but analogously, there are different ways to approach elevated MCV in patients on MTX.

Usually, in patients on AZA, there are alternate immunosuppressant agents to use.