SDHB and neoplasm: Over the next few years, mutations in the other three SDH genes (A, B and C) and its assembly factor (SDHAF2) were also observed, adding considerable evidential weight to SDHx genes being critical tumour suppressors linked to PPGL (Astuti et al. 2001; Burnichon et al. 2010; Hao et al. 2009; Niemann and Muller 2000).