SDHB and neurofibromatosis type 1: Sporadic mutations, which have been reported in only Rearranged during transfection, von Hippel-Lindau, Neurofibromatosis type I, MYC-associated factor X, hypoxia-inducible factor 2A, and recently SDHB and SDHD, explain the remaining 60% of cases, and more than one-third of those cases are associated with a somatic alteration in a predisposing gene.[4] The SDHx group of genes, which are tumor-suppressor genes, encode the subunits of succinate dehydrogenase (SDH) (SDHA, SDHB, SDHC, and SDHD).