SDHB and Onset: Inherited predisposition to PCC/PGL is associated with constitutional pathogenic variants (PVs) in >15 genes, including SDHA, SDHAF2, SDHB, SDHC, SDHD, VHL, FH, MAX, TMEM127, RET, MEN1, and NF1. 4,7 Among the Mendelian PCC/PGL cases, the most sizable contribution is from PVs in SDHB followed by SDHD. 4,8 Associations with subphenotypes of head-and-neck paragangliomas, namely multiple, familial, and/or young-onset disease, have been reported with underlying germline PVs in SDHA, SDHB, SDHC or SDHD (SDHx) and with metastatic disease for SDHB PVs.9