Neurofibromatosis type 1 (NF-1), a phacomatosis with an incidence of 1:3,000-4,000, is characterized by multiple benign nerve tumors, skin café-au-lait spots and a variety of other dysplastic abnormalities, e.g., of blood vessels. On rare occasions NF-1 is associated with arterial dysplasia (vascular neurofibrosis), which is poorly defined and can result, e.g., in stenosis, rupture, arterio-venous fistula, or the formation of aneurysms. Although a rare feature of neurofibromatosis, haemorrhage, e.g., after minimal trauma, is a potentially lethal complication of this disease. We report the case of a 40-year-old woman with a history of NF-1 who collapsed gasping for air and died subsequently. Autopsy revealed a massive cervicomediastinal haematoma with compression of the neck region due to a vessel rupture without an adequate trauma. This fatality demonstrates that, in rare cases of NF-1 patients, the possibility of internal haemorrhage due to vessel rupture being the cause of death should be taken into consideration in medicolegal investigations even as a spontaneous event in the absence of an adequate blunt trauma.