Have had mild anemia and low platelets for at least 15 years before becoming symptomatic. Imuran hit my blood after 18 months and lowered my RBC, WBC, and platelet counts so it was reduced from 150mg to only 50. Numbers have been stable for the past 18 months and eventually I will stop taking imuran but probably not for another year.
Imuran is a cytotoxin, a poisin and can be a problem for some. However, most tolerate it well for indefinite use. All the immuno suppressants are powerful meds that can cause serious problems with some individuals.
Bill