Neurofibromin, the normal protein product of the affected allele, serves to negatively regulate the ras-oncoprotein, resulting in tumor suppression. As a result of the NF1 mutation, individuals with neurofibromatosis are prone to develop other tumors, including carcinoids and pheochromocytomas. Occurring in approximately 0.7% of patients with neurofibromatosis, pheochromocytoma most often appears as a solitary adrenal tumor, but 10% are bilateral. Classic presentation includes headache, sweating, and tachycardia. Hypertension from oversecretion of catecholamines (epinephrine and norepinephrine) can lead to hypertensive urgency and emergency. With hypertension and underlying vasculopathy, patients with neurofibromatosis are at increased risk of vessel rupture with subsequent hemorrhage, such as hemothorax.