SDHB and pheochromocytoma: Although we detected evidence for partial SDHB promoter methylation using the sensitive MSP technique in a subset of phaeochromocytomas, this degree of methylation did not impair SDH activity (for comparison, Gimenez-Roqueplo et al (2002) found a mean QCCR/SCCR ratio of >200 in phaeochromocytomas with SDHB mutations and 2.7 in phaeochromocytomas without SDHB mutations).