 treatment collagen diseas cytostat 22 patient collagen diseas 3 patient immunolog diseas treat cytostat antimetabolit 'purinethol' 6-mercaptopurin 'imuran' azathioprin averag period month rang eleven month improv 17 patient 20 22 patient long-term glucocorticoid medic steroid therapi perman discontinu seriou complic occur form death pancytopenia sepsi treatment requir care supervis patient institut strict indic altern long-term glucocorticoid medic 