[From gene to disease: introduction].

The knowledge of the molecular basis of many diseases is expanding rapidly. Consequently, molecular pathophysiology is becoming an integral part of all medical specialisms. In the evaluation of the relation between genes and diseases many aspects have to be considered: clinical manifestations of disease, gene structure, structure and function of the molecule encoded by the gene and molecular epidemiology in order to dissect the impact of molecular alterations in the population. In the series 'From gene to disease' these clinical, molecular and epidemiological aspects will be described for a number of diseases.