Hypophosphatasia is characterized by defective bone mineralization associated with impaired activity of the tissue non-specific alkaline phosphatase (TNSALP) due to mutations in the TNSALP gene. We describe a child with a mutation that has not been described up to now.A 4-year-old child presented with clinical symptoms of rickets and premature loss of decideous teeth. Reduced serum alkaline phosphatase activity and radiographic features led to the diagnosis of hypophosphatasia, which was confirmed by genetic investigation. The molecular study showed two missense mutations, of which one is a novel mutation.Hypophosphatasia is suspected in a child with rickets and premature loss of decideous teeth. Such symptoms should prompt the search of a reduced serum alkaline phosphatase activity. The clinical and molecular diagnosis of the disease is important for the genetic counseling but also for a proper determination of prognosis, as it is related to the type of mutation.