Normalization of Hypercalcemia Following Successful Treatment of Bilateral Pheochromocytomas Due to A MAX Gene Mutation

ABSTRACT Objective: Pheochromocytoma (PCC) is one of the most heritable tumors known. Currently, 14 gene mutations have been linked with familial PCC. This report describes a novel mutation in one of these known PCC-predisposing mutations. Methods: A patient was diagnosed with bilateral PCCs following discovery of elevated 24-hour urine catecholamines and an abdominal computed tomography scan demonstrating bilateral adrenal masses. Pre-operatively, the patient was found to have elevated serum calcium and calcitonin levels, raising the possibility of multiple endocrine neoplasia (MEN) type 2. The patient underwent a bilateral total adrenalectomy. Postoperative genetic testing was performed. Results: Genetic testing for mutations in the RET proto-oncogene was negative. Serum calcium and calcitonin levels returned to the normal range postoperatively. Repeat genetic testing at a later date revealed a novel heterozygous MYC-associated factor X (MAX) gene mutation (c.3G>A). Conclusion: Testing for mutations in the MAX gene should be considered in patients with bilateral PCC, especially those with a family history of the condition. In addition, caution should be taken when interpreting pre-operative serum calcium and calcitonin levels in patients with PCC to avoid misdiagnosis of MEN type 2 as levels may return to normal following successful treatment. Abbreviations: MAX MYC-associated factor X; MEN multiple endocrine neoplasia; PCC pheochromocytoma; PGL paraganglioma; PTH parathyroid hormone