SDHD Gene Mutations: Looking Beyond Head and Neck Tumors

ABSTRACT Objective: Succinate dehydrogenase complex, subunit D (SDHD) gene mutations are most commonly associated with head and neck paragangliomas. We describe a pair of cases with early-onset, bilateral pheochromocytoma (PCC) and paraganglioma (PGL) syndrome associated with SDHD mutation. Methods: We describe 2 cases of hereditary, early-onset, bilateral PCC/PGL syndrome associated with SDHD mutation. Results: Both cases presented under the age of 30 with bilateral PCC and PGL with SDHD mutations. Case 1 is a female who was initially diagnosed with hypertension and later work-up revealed elevated norepinephrine levels. Positron emission tomography coupled with computed tomography showed avid uptake of fluorodeoxyglucose by the right adrenal gland, the organ of Zuckerkandl, and the left carotid bifurcation. Surgical resection was performed and resulted in normalization of her catecholamines. Case 2 is a male who similarly presented with hypertension and elevated norepinephrine levels. Imaging revealed head, neck, and abdominal PGL. He underwent staged adrenal-ectomies and abdominal PGL resection. Gene sequencing and deletion/duplication analysis revealed that case 1 had an exon 2 deletion in her SDHD gene and case 2 had a frameshift mutation resulting in a stop codon in exon 3 in his SDHD gene. Conclusion: While SDHD mutations are primarily thought to result in silent head and neck tumors, our cases indicate that they should also be considered in the evaluation of functional, bilateral adrenal PCC in young patients. Abbreviations: FDG fluorodeoxyglucose PCC pheochromocytoma PGL paraganglioma SDHD succinate dehydrogenase complex, subunit D gene VHL von Hippel-Lindau