[Rare diseases: unraveling the biological bases to find future therapies].

Rare diseases are characterized by low prevalence and high complexity, affecting millions globally. Although technologies like massive sequencing improve diagnose, therapeutic options remain largely symptomatic or palliative, with few curative treatments approved. In the context of rare diseases, especially genetic neurodevelopmental disorders, therapy development faces obstacles such as phenotypic variability, diverse molecular mechanisms, and complexities in assessing neurodevelopment in natural history and clinical trials. Current strategies include drug repositioning, biomarker development, and a multilateral approach in seeking solutions, offering hope. This work reviews various strategies in developing therapies, from gene therapy and epigenetic therapies to identifying biological targets.