New mechanisms are responsible for the pathogenesis of SCD: the neuropathological lesions in the totally gastrectomized rats are not only due to mere vitamin withdrawal but also due to the overproduction of the myelinolytic tumor necrosis factor- (TNF-) α and the reduced synthesis of the two neurotrophic agents, epidermal growth factor (EGF) and interleukin-6. This evidence concerns the gene EGF and Schnyder corneal dystrophy.