Niemann-pick types a/b
How is Niemann-Pick disease (SMPD1-associated) inherited?
We each have 2 copies of the SMPD1 gene, one we inherit from our mother and one from our father. We only need 1 copy of the SMPD1 gene to work in order for our cells to work properly. In order to have Niemann-Pick disease (SMPD1-associated), both copies of the SMPD1 gene need to have changes or mutations that make the gene not work properly. This is called "autosomal recessive" inheritance. The changes in the two copies of the SMPD1 gene can be the same change or different type of changes/mutations. As long as both changes make the gene work less or not at all, the person will have Niemann-Pick disease (SMPD1-associated).
Someone who only has 1 change/mutation in SMPD1 is known as a "carrier." Therefore, the parents of a person with Niemann-Pick disease (SMPD1-associated) are both carriers of a change in the SMPD1 gene. When both parents are carriers, there is a 25% chance with each child that they will inherit both non-working copies of the SMPD1 gene and develop Niemann-Pick disease. Additionally, each child will have a 50% chance to inherit one copy of the non-working SMPD1 gene and also be a carrier.