A new registry has been launched for people with conditions caused by mutations in the gene for fukutin-related protein (FKRP). This includes people with the type 2I form of limb-girdle muscular dystrophy (LGMD) and the type 1C form of congenital muscular dystrophy (CMD) and, in rare instances, the congenital muscular dystrophies muscle-eye-brain disease and Walker-Warburg syndrome.
It isn’t known why the CMDs cause muscle weakness earlier than other types of muscular dystrophy. One possibility is that the muscle proteins affected in CMD are required early in the development of an infant’s muscle, while muscle proteins linked to other muscular dystrophies don’t become important until the muscles begin to get a lot of use as a child grows.
A diagnosis of CMD can be confusing because for many years the term was used as a “catch-all” name to describe conditions that looked like other muscular dystrophies, but started much earlier or followed different patterns of inheritance.
At least 30 different types of CMD are now recognized (see the Types of CMD chart). At first glance, the various types of CMD seem to have little in common other than their early onset. But on the molecular level, the types can be grouped how their faulty protein affects cells.
A very small group of CMDs are linked to proteins that affect what happens inside muscle fibers, affecting how the fibers process signals from the nervous system, for example, or how they handle calcium.