Hypophosphatasia with premature shedding of teeth and aplasia of cementum

Abstract

Two siblings and a third unrelated child, all under 2 years of age, were examined because of a history of unexplained premature exfoliation of deciduous incisors. One child displayed skeletal deformities and had difficulty in standing and walking at 23 months of age. The three patients were hospitalized so that blood, urine, and radiological studies as well as a thorough physical examination might be made. In addition to premature loss of the deciduous incisors, all patients consistently demonstrated abnormally low serum levels of alkaline phosphatase. These two findings are characteristic of hypophosphatasia, an “inborn error of metabolism” of hereditary nature which effects the skeletal system, teeth, and other organ systems. Other diseases resulting in premature exfoliation of deciduous teeth were ruled out. Microscopic examination of exfoliated teeth from the three children revealed absence, hypoplasia, or dysplasia of cementum. It is suggested, therefore, that premature exfoliation of teeth in patients with hypophosphatasia is due to aplasia of cementum. The effect of this aplasia is to deprive the tooth of its normal periodontal membrane attachment, which leads to spontaneous exfoliation of the tooth. The possible relationship between defective cementogenesis and diminished alkaline phosphatase is discussed.