What Is GNE Myopathy?
GNE myopathy, caused by mutations in the GNE gene, is an inherited disease that disrupts a specific enzyme involved in the production of sialic acid. Without appropriate amounts of sialic acid, cells cannot move, attach to one another, or signal each other properly.
Individuals with GNE myopathy have a progressive weakening of the legs and arms, typically beginning in the late teens or early twenties and almost always before the age of 40. Typically individuals with the disease lose the ability to walk 20 years after symptoms appear. The muscles of the lower leg are typically affected first. As these muscles slowly weaken, walking becomes more difficult and the patient's gait changes. The weakness will spread to the thighs, hand muscles, and certain muscles of the shoulder and neck. A small number of individuals will also have weakness in the facial muscles. Often the large thigh muscles (quadriceps) are unaffected until late in the course of the disease.
For reasons not well understood, a small number of individuals with GNE mutations do not have symptoms of the disease.
How Common Is GNE Myopathy?
Roughly 220 individuals with GNE myopathy have been reported in medical literature. GNE myopathy is most common among Middle-Eastern Jews, particularly of Iranian descent. The disease has also been found in small numbers of non-Jews, both within and outside of the Middle East. Studies estimate that among Iranian Jewish communities in Israel and Los Angeles, 1 in every 500 to 1000 are affected by GNE myopathy.
How Is GNE Myopathy Treated?
There is no cure or treatment for GNE myopathy that can reverse or delay the progression of muscle weakness. Neurologists, rehabilitation specialists, and physical and occupational therapists can aid in relieving symptoms as they appear.
What Is the Prognosis for an Individual with GNE Myopathy?
The disease often does not cause noticeable symptoms until the late teens or early twenties, when muscle weakness begins. Movement of the arms and legs will become progressively impaired, and typically people with GNE myopathy are wheelchair-bound 20 years after symptoms begin. The disease's effect on lifespan is not well studied.