The lack of animal models that mimic human disease impedes the study of many pathologies that still lack treatment beyond symptom relief. This is what has happened so far with PURA syndrome, a rare disorder affecting brain development for which a mouse model has finally been developed. Other times, small and large models exist, but an effective treatment remains elusive, as is the case with Krabbe disease, a fatal disease in children that could be prevented with the advances in gene therapy.