SDHD and pheochromocytoma: Germline mutation of the succinate dehydrogenase subunit genes, SDHA, SDHB, SDHC or SDHD, is associated with increased risk for paraganglioma (PGL), pheochromocytoma (Pheo), gastrointestinal stromal tumor (GIST) and renal cell carcinoma [15–18].