Families

FEM1C is a gene that helps cells break down proteins they no longer need or that have been damaged. Usually, FEM1C looks for a short “signal” at the end of certain proteins (often involving the amino acid arginine) and directs those proteins to be cleared away. However, when FEM1C itself is altered—specifically at a spot called Asp126 (leading to variants known as Asp126His or Asp126Val)—it can’t recognize these proteins properly anymore. As a result, those proteins may build up and contribute to neurological symptoms.

So far, only a few people have been identified with changes in FEM1C. Individuals with these variants tend to have severe developmental delays, difficulties with speech (some have no speech at all), and movement problems such as increased muscle tightness and trouble with coordination (ataxia). It also appears that these changes often arise for the first time in the child (de novo), but we don’t yet know whether there are other ways it can be inherited. Because so few cases are known, we also don’t know exactly how common this condition is.