FRI227 Functional Transformation Of An Initially Non-functional Paraganglioma In A Patient With Cyanotic Congenital Heart Disease

Disclosure: M. McConnell: None. M. Kanin: None. M.S. Auerbach: None. R. Yu: None. Background: Most pheochromocytomas and about half of paragangliomas (P-PGLs) are functional in that they produce catecholamines. Transformation of non-functional to functional P-PGLs is exceedingly rare. We present a case of such transformation in a young male with cyanotic congenital heart disease (CCHD), resulting in catecholamine-induced cardiomyopathy. Clinical Case: A 27-year-old male with CCHD presented to the hospital with tachycardia, hypertension, and hypoxia. He had a newly depressed ejection fraction of <20% and was in florid heart failure. Despite intervention, he decompensated rapidly, requiring extracorporeal membrane oxygenation (ECMO). Five years prior to this presentation, he had had normal 24-hour urine fractionated metanephrines, vanillylmandelic acid (VMA), and homovanillic acid (HVA) levels; on imaging, he had been incidentally found to harbor a 3.3 x 1.6 x 2.5-cm nodule in the upper aortocaval space which could represent a paraganglioma. Subsequent imaging showed slow growth of this mass. Given this pertinent history, urine and plasma free metanephrine studies were repeated during the hospitalization while he was not on vasopressors. 24-hour urine normetanephrines were elevated at 2,644 mcg/d (81-667 mcg/d), metanephrines at 405 mcg/d (55-320 mcg/d) while plasma free metanephrines were elevated at 0.92 nmol/L (0-0.49 nmol/L) and normetanephrines at 11.85 nmol/L (0-0.89 nmol/L). DOTATATE PET/CT revealed a soft tissue mass measuring 4.3 x 3.1 x 4.9 cm with intense DOTATATE activity in the right paravertebral space between the aorta and cava. He was treated with alpha-adrenergic blockade with improvement in blood pressure. Two months later, he underwent resection of the mass with pathology confirming a 4.9 cm paraganglioma. Conclusion: It is very rare for a paraganglioma to undergo transformation from non-functional to functional status although it is reported in the literature. This scenario is supported by our patient’s normal 24-hour urine metanephrines, VMA, and HVA results on initial presentation followed by marked elevation in urine and plasma metanephrines 5 years later when he presented with heart failure. The functional transformation in this patient was accompanied by significant growth of the paraganglioma. We surmise that alterations in gene expression during tumor growth may be responsible for the functional transformation. It is crucial to reassess the functionality of a paraganglioma if the clinical condition suggests catecholamine excess. Presentation: Friday, June 16, 2023