Mutations in tumor-suppressing genes encoding subunits of the succinate dehydrogenase (SDH) complex (SDHA, SDHB, SDHC, and SDHD, i.e. SDHx genes) and the required assembly factor that flavinates SDHA (SDHAF2) can inhibit SDH activity and thereby cause hereditary and (apparently) sporadic PPGL [4–9]. The gene discussed is SDHA; the disease is neoplasm.