Through the examples above, we can begin to see how rare diseases may shed light not only on more common conditions but also on each other. Disorders such as FOP, POH, MAS, and AHO provide a fertile molecular neighborhood for investigating a disease such as POH. Will POH be linked to the G proteins, c-fos, the BMPs, the BMP receptors, or perhaps an as yet undiscovered gene? For the moment, there are few answers, but there are at least some tantalizing questions to ponder and investigate. We all look forward to the day when our knowledge of, and treatment for, diseases like POH will be more than just skin and bones.