CASE REPORT published: 20 August 2019 doi: 10.3389/fendo.2019.00546 Frontiers in Endocrinology | www.frontiersin.org 1 August 2019 | Volume 10 | Article 546 Edited by: Krzysztof Reiss, LSU Health Sciences Center New Orleans, Louisiana State University, United States Reviewed by: Luis Del Valle, LSU Health Sciences Center New Orleans, Louisiana State University, United States Salah A. Mohamed, Department of Cardiac and Thoracic Vascular Surgery, University Medical Center Schleswig-Holstein, Germany *Correspondence: Isabelle Bourdeau isabelle.bourdeau@umontreal.ca Specialty section: This article was submitted to Cancer Endocrinology, a section of the journal Frontiers in Endocrinology Received: 11 June 2019 Accepted: 22 July 2019 Published: 20 August 2019 Citation: Parisien-La Salle S, Dumas N, Rondeau G, Latour M and Bourdeau I (2019) Isolated Pheochromocytoma in a 73-Year-Old Man With No Clinical Manifestations of Type 1 Neurofibromatosis Carrying an Unsuspected Deletion of the Entire NF1 Gene. Front. Endocrinol. 10:546. doi: 10.3389/fendo.2019.00546 Isolated Pheochromocytoma in a 73-Year-Old Man With No Clinical Manifestations of Type 1 Neurofibromatosis Carrying an Unsuspected Deletion of the Entire NF1 Gene Stefanie Parisien-La Salle 1 , Nadine Dumas 2 , Geneviève Rondeau 1 , Mathieu Latour 3 and Isabelle Bourdeau 1 * 1 Division of Endocrinology, Department of Medicine, Research Center, Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, QC, Canada, 2 Division of Genetics, Department of Medicine, Research Center, Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, QC, Canada, 3 Department of Pathology and Cellular Biology, Centre Hospitalier de l’Université de Montréal (CHUM), Montreal, QC, Canada Pheochromocytomas (PHEOs) are a rare cause of endocrine hypertension that requires genetic counseling since at least 30% of PHEOs are associated with a germline mutation in a susceptibility gene. Neurofibromatosis type 1, NF1 is amongst the 16 known causing genes for pheochromocytomas/paragangliomas. We report a case of a 73-year-old man with PHEO in whom genetic testing revealed a large pathogenic heterozygous deletion of 1.14 Mb encompassing the entire coding sequence of the NF1 gene while the patient showed no signs of clinical NF1.This case illustrates that the diagnosis of NF1 should not be excluded in patients with PHEO in the absence of clinical diagnosis of the disease and support that older patients with PHEO should also be offered genetic counseling. Keywords: neurofibromatosis, deletion, phenotype, pheochromocytoma, hypertension INTRODUCTION Pheochromocytomas (PHEOs) are rare catecholamine-secreting tumors that can cause endocrine hypertension with a prevalence of 0.4–2% in hypertensive patients (1). Germline mutations can be identified in at least 30% of patients with PHEOs and paragangliomas (2). In light of this, genetic testing is now recommended for all patients diagnosed with PHEO (3, 4). Some of these mutations can cause hereditary syndromes such as neurofibromatosis type 1 (NF1), von Hippel- Lindau (VHL), and multiple endocrine neoplasia type 2 (MEN2) (2). NF1 is a neurocutaneous disease caused by a mutation in the NF1 gene that encodes for the neurofibromin protein (5). The NF1 gene is located on the chromosome 17q11.2 (2). Two of the following criteria are needed to establish the diagnosis of NF1: inguinal or axillary freckling, two or more neurofibromas, six or more café-au-lait macules, two or more Lisch nodules, optic gliomas, distinctive bone lesions, or a first degree relative with NF1 (6). We report here the case of a man with pheochromocytoma that was diagnosed at 73 years-old carrying an unsuspected NF1 gene deletion but with no clinical manifestations of NF1. Abbreviations: PHEO, Pheochromocytoma; NF1, Neurofibromatosis type 1.