Background
Paraganglioma pheochromocytoma predisposition syndrome is an inherited susceptibility for head and neck paragangliomas and pheochromocytomas, both of which may be malignant, in addition to renal cell cancer, thyroid cancer and gastrointestinal stromal tumour. We present the diagnostic dilemma of a SDHB pathogenic variant-related paraganglioma with elevated catecholamine metabolites in the setting of dopamine agonist therapy and the associated management issues of pre-operative blockade.
Case
A 79 year old lady with advanced Parkinson’s disease managed with a continuous Duodopa infusion was incidentally found to have a right extra-adrenal lesion and elevated plasma 3-methoxytyramine (3-MT) 890pmol/L (RR<181) and urinary 3-MT 67.7umol/d (RR<1.3) with otherwise normal catecholamine metabolites. She underwent a laparascopic resection of the paraganglioma with a partial right adrenalectomy, yet her post-operative plasma 3-MT remained elevated at 1670 pmol/L (RR<181). She was later noted to have a new Dotatate PET avid pancreatic lesion and has since been found to have a SDHB gene causing paraganglioma pheochromocytoma predisposition syndrome.
Discussion
SDHB pathogenic variant-related paragangliomas typically secrete norepinephrine rather than epinephrine, and some can secrete dopamine. In biochemically functioning paragangliomas, the sensitivity of 24 hour urinary measurements of dopamine was 18%. This case highlights the difficulties with interpreting elevated catecholamine metabolites in a patient with phaeochromocytoma paraganglioma predisposition syndrome in the setting of continuous dopamine agonist therapy.
The US Endocrine Society recommends that all patients with a hormonally functional PPGL should undergo preoperative blockade to prevent perioperative cardiovascular complications such as an alpha-adrenergic receptor blocker. However, the current evidence suggests that adrenergic blockade is contraindicated in dopaminergic phenotype phaeochromocytoma / paragangliomas (PPGLs) due to the risk of cardiovascular collapse. This emphasises the need to revise the current perioperative management guidelines for dopaminergic phenotype PPGLs.