Update on clinical gene therapy in childhood.

The successful use of gene therapy to correct rare immune system disorders has highlighted the enormous potential of such therapies. We review the current state of gene therapy for childhood immune system disorders, and consider why these conditions have been particularly amenable to genetic correction. As with all emerging therapies, there have been unexpected side effects and their underlying mechanisms are the subject of intense research. Minimising such risks through improved vector design will play an important role in developing the next generation of gene based therapies and extending their applicability.