ABSTRACT

49, XXXXY syndrome is the most severe and rare form of Klinefelter syndrome. The number of cases of oral and dental findings with this syndrome is very little. The aims of our case report are to present oral and dental findings of the syndrome about which we have limited knowl edge, to support other case reports, and to evaluate the relationship between this syndrome in which hypodontia is seen and the MSX1 gene that is associated with hypodontia. A clinical and radiographic examination was performed on an 11-year-old patient who had been taken to a practitioner at age 1 for delayed development, diagnosed with 49, XXXXY syndrome by chromosome analysis, and exhibited characteristic features of the syndrome. Congenital miss ing permanent teeth, hypertaurodont primary and permanent teeth, delayed tooth development and mandibular prognathism were observed in the examination. Whether there were any muta tions in the MSX1 gene was researched, and the association with this syndrome was evaluated.