Sofia Jarvis, seen here with her family at a press conference in February, is one of several dozen children in California who have been diagnosed with a rare paralytic syndrome. It has left her left arm paralyzed. Martha Mendoza/AP hide caption

itoggle caption Martha Mendoza/AP

Tom Murphy, 56, in his home in Gainesville, Va., was diagnosed with ALS four years ago. An experimental drug seems to have slowed the progression of his disease, he says, though most ALS patients aren't as lucky. T.J. Kirkpatrick for NPR hide caption

itoggle caption T.J. Kirkpatrick for NPR

Surgeons at Methodist University Hospital in Memphis prepare to transplant a liver in 2010. Karen Pulfer Focht/The Commercial Appeal/Landov hide caption

itoggle caption Karen Pulfer Focht/The Commercial Appeal/Landov

One of the scariest parts of advanced macular degeneration can be losing the ability to read facial expressions. Maria Pavlova /iStockphoto hide caption

itoggle caption Maria Pavlova /iStockphoto

Lissette Encarnacion in her apartment at The Brook, a supportive housing complex in the New York City borough of the Bronx. Natalie Fertig/WNYC hide caption

itoggle caption Natalie Fertig/WNYC