SDHB and paraganglioma: In the Netherlands, 90% of the patients with head and neck paraganglioma have a pathogenic variant in the SDH gene encoding for the SDHA, SDHB, SDHC, SDHD, or SDHAF2 subunits.6SDHD and SDHAF2 have a parent-specific penetrance; paragangliomas are only present after paternal transmission.7The most common pathogenic variants are found in SDHD and SDHB.