Development of patient-tailored prognostic and therapeutic strategies remains a major, yet largely unmet, goal of medicine. Studies performed in patients who carry mutations in the Wiskott-Aldrich syndrome protein (WASP) gene have indicated the feasibility, but also the limitations, of this approach. In this review, we discuss the importance of specific WASP mutations, and their effects on protein expression and function in determining the spectrum of clinical phenotypes associated with WASP defects. The array of currently available and foreseeable therapeutic options is reviewed in this context as a model for other more common genetic disorders.