Hello Jen,

Spontaneous mutations are rare but possible.  It is more probable that your husband has a mutation not in the top 95% of what is tested for but can still be there.  My husband, daughter, and I were tested and at first came back as not having any mutations.  Considering my daughter is obviously a salt-waster (as her body tells us daily),  they knew to sequence the genes and look for more rare types. My husband and I had two different rare types and our daughter inherited them both. 

Hope that helps,

 

RebeccaM