Infantile congenital agranulocytosis or Kostmann syndrome is a rare hereditary kind of severe neutropenia. The typical symptoms, which appear since the first days of life, are abscesses located on various parts of the body: ear, cutis, lung and oral cavity. These abscesses are due to an almost total disimmunity typical of the neutropenia. The aim of this article is to describe the most typical signs of this pathology in the oral cavity, reporting a case observed in our department in Florence, Italy. On the basis of the personally observed case and of the review of the literature, it is possible to consider, as a characteristic finding in Kostmann syndrome, a typical very serious periodontal pathology, which is similar to the prepubertal periodontitis in deciduous dentition. At the age of 19 years the patient showed a dramatic compromise of the masticatory function. It is obvious that the lack of response of the host can obstruct the interaction between the host and the microbic flora, because the lack of neutrophils increases the susceptibility of the patient to every kind of infection, even to periodontitis. A periodontal prophylaxis, since the very first observations, followed by a rigorous maintenance with frequent and regular professional hygienic treatments could be effective in controlling the effects of periodontal disease and could reduce the tragic evolution. We need to recognise that it could be hard to monitor the oral situation correctly in these patients, as they have a continuously poor systemic condition. Finally in these cases the rehabilitative therapy is very problematical.