TYMP and neuropathy, small fiber: Various theories have been put forward for the etiopathogenesis of HFS: increased expression of thymidine phosphorylase, which converts capecitabine to active 5-FU in keratinocytes leading to inflammation,[7] excess collection and secretion of the drug by eccrine sweat glands which are highly concentrated on the palms and soles,[8] and the latest research findings which claim that small-fiber neuropathy is the likely cause of neuropathic symptoms encountered in the condition.