In cardiac transplantation, mild acute rejection
grades 1A and 1B) is often not treated with increased
immunosuppression. In contrast, multifocal moderate or severe
(IHLTS grade 3 and 4)
are almost uniformly
treated with augmented immunosuppression. Therefore, the
histopathological distinction between mild and moderate is
practically important for patient management.
The most useful histopathological features used to
distinguish between mild and aggressive multifocal rejection are
the severity of the inflammation, myocyte necrosis and the
presence of segmented leukocytes (especially eosinophils). As
the rejection reaction worsens, one can see focal areas of
myocyte necrosis, edema, interstitial hemorrhage and
occasionally a frank vasculitis.