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Competing Interests: G. Baujat et A. Bloch-Zupan déclarent des liens ponctuels avec Alexion. G. Baujat et A. Bloch-Zupan déclarent des liens ponctuels avec Alexion. S. Ursprung déclare n’avoir aucun lien d’intérêts.

Hypophosphatasia (HPP) is an inborn metabolic bone disorder caused by loss-of-function mutations in the gene encoding tissue nonspecific alkaline phosphatase (TNSALP). The adult form can be mistaken with common osteoporosis and/or present recurrent metatarsal fractures, skeletal and muscular pain. Subtrochanteric femoral pseudofractures resembling bisphosphonate-associated atypical femoral fractures can also be present, and Bps are therefore contraindicated in HPP. Early tooth loss and renal calcifications can orient towards the diagnosis. The diagnosis is based on low serum ALP levels (< 40 U/L) and high ALP substrate levels, such as vitamin B6 (pyridoxin), eventually on genetic testing. Recent development of an enzyme replacement therapy offers new therapeutic perspectives in severe cases., Competing Interests: Les auteurs n’ont déclaré aucun conflit d’intérêt en relation avec cet article.

Background: Hypophosphatasia is a rare inherited disorder characterized by defective bone and teeth mineralization and deficiency of serum and bone alkaline phosphatase activity. Several mutations in the TNSALP gene are identified., Aim: The authors describe a Tunisian case having a mutation that has not been described up to now., Case: It is about an infant, in the antecedents of recurring disease of the lungs in child since the age of seven months, which presents clinical and radiological signs of rickets. The diagnosis of hypophosphatasia is strongly suspected in front of Reduced serum alkaline phosphatase activity and confirmed by the genetic study. The child is homozygous for a new mutation L282P in the ninth exon of the gene. The parents and two brother and sister are heterozygous for the same mutation.

Unlabelled: 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., Case Report: 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., Conclusion: 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.

Hypophosphatasia is a rare inherited disorder characterized by defective bone and teeth mineralization and deficiency of serum and bone alkaline phosphatase activity. The symptoms are highly variable in their clinical expression, which ranges from stillbirth without mineralized bone to early loss of teeth without bone symptoms. Currently, there is no treatment for the disease. Recent developments in molecular biology allow to better understand the genetics of the disease, especially its transmission that may be recessive or dominant, to improve genetic counseling and molecular diagnosis, and offer new perspectives of treatment.

A case of hypophosphatasia with osteomalacia and subtrochanteric pseudo-fractures is described in a 53 years old woman. Bone biopsy showed an excess of osteoid. Alkaline phosphatase activities in sera were low. There was no excretion in the urine of abnormal quantities of phosphoetanolamine. But alkaline phosphatase activities were low in bone and intestine. Two sons were affected by biological hypophosphatasia without clinical features. These data support the diagnosis of minimal hypophosphatasia in an adult.

Two very dissimilar cases of hypophosphatemia in the adult patient are described by the authors. The first case was symptomatic since childhood, with typical clinical and radiologic findings (fissures, diaphyseal bone spurs, bony deformities), whereas the second case was minimally symptomatic (loss of teeth and back pain). Articular chondrocalcinosis was observed in both cases, as was a decrease in alkaline phosphatase and the increased urinary excretion of phosphoethanolamine. Histological examination demonstrated an increase in osteoid. Review of the literature revealed 40 cases of this inborn error of metabolism seen in adulthood, enabling a detailed description of the characteristics of this polymorphic condition.