Endocrine Abstracts

Background: Patients with Phaeochromocytomas (PCC) have been found to carry germline mutations in 40% of cases. The number of known susceptibility genes has risen sharply in recent times, from six to sixteen since 2009. We present a patient who was found to have a mutation in Myc Associated Protein X (MAX), one of the newly identified inherited susceptibility genes.

Case Presentation: A 16-year-old female presented with paroxysmal episodes suggestive of catecholamine excess and a seizure with labile blood pressure. Subsequently, a PCC was identified in the right adrenal gland which was later removed. Ten years later, follow up showed high urinary noradrenaline levels and a PCC was confirmed in the contralateral gland. Following a left adrenalectomy, genetic testing showed no mutation in any of the known susceptibility genes at the time. However, twelve years later repeat genetic testing identified a mutation in the MAX gene.

Discussion: MAX is a tumour suppressor gene involved in the MYC pathway and is mutated in approximately 1.12% of PCC cases. Current guidance states that the decision for genetic testing should be driven by the clinical features that the patient presents with e.g. bilateral disease, young age and a family history. Testing of the different susceptibility genes should be done depending on the location of disease and specific hormonal production. Our case illustrates the importance of repeat genetic testing to identify germline mutations in genes which at the time of presentation had not been linked to the patient’s condition. Identification of patients with germline mutations is important as it enables the early diagnosis and treatment of relatives. This is especially advantageous if family members can be identified prior to metastasis, which occurs in 10% of MAX mutated cases.