A recent study of patients with SDHD-linked head and neck paragangliomas [39] showed that both catecholamine excess and extra-adrenal paragangliomas/pheochromocytomas in this group are higher than previously thought, suggesting that SDH related tumors show distinct [13] but still broadly overlapping phenotypes. This evidence concerns the gene SDHB and hereditary pheochromocytoma-paraganglioma.