The article reports a lethal case of a patient who rapidly developed clinical manifestations of late neurosyphilis with underlying conservative and operative treatment for fibro-cavernous pulmonary tuberculosis. The death was caused by neurosyphilis. The attending doctors, including phthisiatricians, surgeons, neurologists, and even dermatovenereologist did not attribute the patient’s seropositivity to developing neurological symptoms. Belated diagnosis of ischemic stroke and late initiation of a specific treatment predetermined poor outcome. The authors draw attention of the aforementioned medical specialists to the fact that qualified pathoanatomical study and histological validation of specific injuries of the brain and other organs and tissues involved in the specific process is highly important. Treponema pallidum was detected in lesion foci by special staining methods, which validated the etiology of the disease. The article emphasizes the advisability of more extensive use of histologic and etiologic validation of the diagnosis, which is not commonly used in the Russian Federation.