SAT561 Pathogenic RET V804M Germline Variant Without Clinical Manifestations Of Multiple Endocrine Neoplasia Type 2 In An Elderly Male

Disclosure: R. Ghosh: None. G. Al-Naqeeb: None. P. Veeraraghavan: None. C. Craig: None. J. Klubo-Gwiezdzinska: None. S. Gubbi: None. Background: Germline pathogenic variants in the RET protooncogene give rise to multiple endocrine neoplasia (MEN) types 2A and 2B. MEN2A is mainly characterized by MTC (∼100%), pheochromocytoma (PHEO; 4% - 88%), and primary hyperparathyroidism (HPTH; 2% - 30%), while MEN2B predominantly manifests with MTC (100%), PHEO (50%), mucocutaneous neuromas, and marfanoid habitus. Both MEN2A and 2B follow an autosomal dominant mode of inheritance. While certain pathogenic RET variants (M918T, A883F, and C634X) have high penetrance and present with aggressive disease, other variants such as V804M are of low penetrance and manifest with clinically mild disease.Clinical case: A 75-year-old male was referred to our center for further evaluation of the finding of an abnormal RET gene that was identified on a peripheral blood whole-exome gene sequencing research panel performed at an outside center. The patient was noted to have a germline RET c.2410 G>A, p.V804M heterozygous pathogenic variant. The patient denied any history of lump in the neck, symptoms of hyper- or hypothyroidism, tremors, headaches, fatigue, facial flushing, palpitations, constipation, diarrhea, anxiety, depression, or history of fragility fractures. Medical history consisted of hypertension, nephrolithiasis, type 2 diabetes mellitus, obstructive sleep apnea, interstitial pulmonary fibrosis, and colonic diverticula and polyps. Family history was significant for leukemia, colon, and breast cancers, but none of the relatives had a history of MTC, PHEO, or MEN2, and his children, while healthy, had not undergone RET germline testing. Physical examination showed no evidence of hypothyroidism or hyperthyroidism. Neck examination showed no evidence of thyromegaly or cervical lymphadenopathy. Laboratory investigations were unremarkable [serum calcitonin: 7.9 pg/ml (NL: </=14.3), CEA 2.8 mcg/L (NL: 0.8-3.4), thyrotropin (TSH): 1.92 microIU/ml (NL: 0.35-4.94), free thyroxine: 0.9 ng/dl (NL: 0.7-1.5), plasma free normetanephrine: 0.31 nmol/L (NL: <0.9), plasma free metanephrines 0.24 nmol/L (NL: <0.5), parathyroid hormone: 28.2 pg/ml (NL: 15-65), and ionized calcium 1.23 mmol/l (NL: 1.09-1.30)]. Thyroid sonogram was normal. We recommended active annual surveillance with biochemical markers and imaging along with genetic testing of the RET gene in his children. Conclusion: The V804M RET variant has been often associated with MTC or MEN2A phenotypes [1]. However, the variable expression of this variant may lead to a mild clinical phenotype or even absence of MTC/MEN2A manifestations. Hence, active surveillance as opposed to radical surgery like prophylactic thyroidectomy would be more beneficial in patients with no clinical or biochemical evidence of disease. Reference: Pinna et al., 2007, V804M is the most frequent mutation and may be associated with FMTC/MEN-2A phenotype. Thyroid, 17(2), 101-104. Presentation Date: Saturday, June 17, 2023