And while the inherited defect itself is rare, its discovery may help researchers unravel the mysteries of much more common paralyzing conditions, from spinal cord injury to Lou Gehrig's disease.
In a paper published online today in the American Journal of Human Genetics, and scheduled for the journal's October issue, the U-M and Penn team describes a new gene, called NIPA1, for a form of hereditary spastic paraplegia, or HSP.
HSP is the name given to a group of disorders affecting about 20,000 Americans. HSP gradually disables its victims as long nerve cells in the spinal cord degenerate and muscles weaken and become spastic. It is often misdiagnosed as other nerve disorders, including multiple sclerosis, cerebral palsy, and amyotrophic lateral sclerosis (also called Lou Gehrig's disease).
There is no cure for HSP, which is also sometimes called familial spastic paraparesis or Strumpell-Lorain disease. Treatment is limited to physical therapy and exercise to help retain as much muscle function as possible, drug treatment to tame spastic muscle movements, and medication to treat patients' bladder and bowel control problems, and depression.
"There are direct overlaps between this group of diseases and the nerve degeneration processes in other disorders," says senior author John Fink, M.D., professor of neurology at the University of Michigan Medical School, who has devoted his career to studying and treating HSP and related conditions. "Not only do we hope this discovery will aid HSP patients, but we also believe it will aid in understanding and perhaps stopping the fundamental processes involved in other types of spinal cord degeneration."