Concerning SDH, its loss-of-function mutations have been detected mainly in two rare tumors, such as paraganglioma and pheochromocytoma [24], and are generally frequent on the two subunits SDHB and SDHC, whereas only few mutations affect the other subunits (SDHA and SDHD) [28]. The gene discussed is SDHB; the disease is paraganglioma.