Additionally, significant numbers of SDHB-affected patients harbor germ line SDHB mutations and suffer from a particularly aggressive form of malignant PPGL (Amar et al., 2005; Timmers et al., 2007), whereas other family members with identical SDH mutations remain free of metastatic disease (see modifier genes above and mev-1 below). Here, SDHB is linked to metastatic neoplasm.