Hypophosphatasia (HPP) is a rare genetic disorder characterized by the diminution of the enzymatic activity of the alkaline phosphatase (ALP). The disease mainly involves multiple defects of the mineralization of the skeleton including bone fragilities. It will be expressed to varying degrees of severity and will allow to characterize different forms of HPP. Unfortunately, the prevalence of this pathology remains probably underestimated and its diagnosis must be multidisciplinary by taking into account the biochemical assays, the clinical history as well as the radiological imaging. So, in the approach of this diagnosis, a retrospective screening was carried out by the clinical chemistry department of the CHU of Liège. The aim of this study is to potentially identify the affected patients on the basis of their biochemical assays and their anamnesis in order to propose a genetic screening. Unfortunately, no case could be formally identified, which testifies the difficulty to establish a diagnosis of the slight forms encountered mainly in the adults.