[Morphological aspects of inopportune fatty metamorphosis of the thymus]

Thymus glands from 43 early infants who died of asphyxia, birth injury and inflammatory diseases were studied morphologically. Unscheduled fatty metamorphosis (UFM) of the thymus was found in 32% of cases of inflammatory diseases. Lipid containing cells of the thymus are thymic macrophages in the state of irreversible lipoid dystrophy and death. Macrophagal enzymopathy with the disturbance of intracellular lipid digestion may account for it. Lipid dystrophy is also noted in some epithelial cells. It is shown that the accumulation of the lipids in thymic macrophages occurs not only in unscheduled fatty metamorphosis, but also during the accidental transformation of the thymus, thus the latter may be considered as a physiologic analogue of UFM. In case of UFM, however, this process acquires a pathologic character and results in macrophage death. Therefore, UFM may be considered as a variant of the accidental transformation abnormality of the thymus.