Induced pluripotent stem cells derived from patients with the neurodegenerative disease called spinal muscular atrophy display characteristics of the disease, according to a paper published today in Nature. Thus, iPS cells look to be fulfilling their promise of being powerful tools to study sickness and screen for drugs to stop it. (See Reprogrammed skins cells are testing ground for new drugs ). iPS cells have been made from patients with a variety of diseases (See Ten diseases in a dish). However, this is the first demonstration I know of that shows that the cells show the phenotype of the disease.