[Predictive medicine].

Predictive medicine is based on the early recognition of a pathologic process before the onset of clinical manifestations, followed by preventive therapy. Prediction can be achieved by identifying disease predisposing genes. However, this approach is usually insufficient because most often the disease is polygenic and the penetrance of genetic factors is incomplete, which reduces the reliability of the prediction. It is very useful when it is possible to complement this prediction by the study of biological markers allowing the detection of the triggering of the pathogenic process, before it has induced significant lesions or functional disturbances at the origin of clinical manifestations. Predictive medicine is only justified when it may lead to preventive therapy as in the exemplary case of juvenile glaucoma. The case of insulin dependent diabetes mellitus is also interesting, even if preventive therapy is not yet routinely available.