[When genetics matters: an unusual case of left-sided hemiparesis].

We report the case of a 35-year-old woman who has been admitted to our emergency room because of the sudden onset of a left-sided hemiparesis. The physical examination showed disseminated teleangiectases on the upper and lower lip, on the mucosal surface of the tongue and on the skin. The cerebral CT scan presented a right-sided fronto-parietal lesion, more likely an abscess, confirmed on surgical removal. A meticulous family history showed the presence of similar clinical features among several family members, raising the certainty about the presence of the Rendu-Osler-Weber disease. This case is highly instructive in emphasizing the value of taking a careful medical history and how doing it is extremely important in our daily practice.