RESUMO
Hypophosphatasia is a rare inherited disorder characterized by deficient activity of tissue non-specific alkaline phosphatase [found in the bone, liver and kidney] which leads to abnormal bone and tooth mineralization. The symptoms are highly variable in their clinical manifestation, ranging from stillbirth without mineralized bone to early loss of primary teeth without bone symptoms. The diagnosis is based on low levels of serum alkaline phosphatase and increased serum or urine concentrations of phosphoethanolamine, pyridoxal 5 '-phosphate and inorganic pyrophosphate. Six clinical forms of Hypophosphatasia are currently recognized: prenatal [lethal], prenatal benign, infantile, childhood, adult and odontohypophosphatasia. A 27-month-old girl was referred to the Paediatric Dentistry Department of Shiraz Dental School with chief complaint of spontaneous loosening and shedding of anterior deciduous teeth. In clinical examination, it was noticed that, teeth number 61, 62, 71, 72 and 81 were absent. There was no sign of gingival inflammation. According to the height and weight curves, growth of patient was below the normal rate. About 1 year delay in the date of her standing or walking capability was recorded in the patient's medical history. Also there was a history of foot pain and early fatigue. CBC, serum alkaline phosphatase and urine phosphoethanolamine tests were requested for the patient. Results showed decreased serum alkaline phosphatase and increased urine phosphoethanolamine. In histological survey of exfoliated teeth, the absence of cementum on root surfaces was detected. Also, the patient's physician reported skeletal deformities and defective mineralization in her hands and feet