We report 3 patients with Proteus syndrome (PS) who died suddenly from pulmonary embolism (PE). The first patient was a male diagnosed with PS at 12 years who had varicose veins, portal vein thrombosis, right iliac vein occlusion and recurrent PE. At age 25 years, he was admitted to the hospital with a severe headache. Despite therapeutic doses of warfarin, investigations for an acute episode of breathlessness showed PE and he was unable to be resuscitated. The second case was a 9-year-old male with PS who collapsed at home and could not be revived. Autopsy revealed that the cause of death was a PE associated with thrombosis of the deep veins (DVT). The third patient was a 17-year-old female undergoing inpatient treatment for sinusitis when she unexpectedly arrested. She could not be revived and a full autopsy revealed a large PE with no identified DVT. We conclude that PE is a serious complication of PS and recommend vigilance concerning the signs and symptoms of thrombosis and PE in individuals with PS, including children. Aggressive evaluation and treatment should be considered urgently in patients with PS and signs or symptoms of DVT.