FUS Inheritance

[MamaT]

Sorry for the long rambling post.

Seven members of my family have died from ALS. The gene that runs in our family is the FUS gene. We thought the disease had mostly burned itself out in our family. However, a cousin was recently diagnosed with ALS at age 26. My grandmother, J, and her sister must have passed on the mutation because they each had a child who died of ALS and tested positive for the FUS mutation. J is the great grandmother of this cousin. His grandmother (J's daughter) recently died at age 79 and did not have ALS. His mother (J's granddaughter) is in her 50's and does not have ALS. His only other relatives who had ALS are his great aunt (J's daughter) and the daughter of this great aunt. Hopefully, that all makes sense.

My mother (J's daughter) is in her late 60's and does not have ALS. The family members in her generation who have gotten ALS died in their 50's. Those in my generation have died in their 30's. I am in my mid-forties with no ALS symptoms. We are both past those benchmarks so we assumed that we were in the clear until this cousin was diagnosed. I have small children and now I'm concerned for their health. The family members in their generation die in their late teens or early twenties.

The recently diagnosed cousin has not had genetic testing done (I think). With the FUS gene, does it often skip generations or is it more the case where if you get the mutation, then you get ALS?

 

[Nikki J]

This is a very complicated question. There are a number of variants in FUS and each has its own pattern. Your answer depends on which one your family carries ( the genetic report should specify). It may be worth discussing with a genetic counselor with ALS expertise.

from what I know FUS mutations are mostly autosomal dominant meaning you only need to have one copy to be affected. A few are recessive meaning you would have to inherit from both sides. Your family pattern sounds autosomal dominant. Another issue is penetrance - how likely a genetic carrier is to get the associated disease. Some forms of FUS are not very penetrant meaning carriers often live normal lifespans without ALS. Your mother had only a 50/50 chance of inheriting the mutation. If she didn’t she couldn’t pass it on and it stops in her line. There is currently a trial for genetic therapy for FUS . It is out of Columbia