A case of familial hypophosphatemic vitamin D-resistant rickets or X-linked hypophosphatemia (XLH) accompanied by specific systemic and dental findings is reported. A 15-year-old boy with XLH visited our facility complaining of a toothache in the left lower canine region. Two other family members of the patient, his younger sister and their mother, also had XLH, whereas the other 2 members, his younger brother and father, are healthy. Those with XLH show systemic signs of the disease, such as growth retardation, limb deformity, and spinal curvature disorders; however, these symptoms are more severe in the patient than in the others. The patient had multiple periodontal abscesses, but no evidence of dental caries, trauma, or periodontal disease on the corresponding teeth at the time of his oral examination. A radiographic examination showed root dysplasia and enlarged pulp chambers.A histologic examination of an extracted third molar showed marked globular dentin and an increased predentin width. The abscess was thought to be caused by pulpal infection, which came from bacterial invasion through enamel cracks and dentinal microcleavage of the teeth. The treatments provided in this case are discussed.