What causes Niemann-Pick type C disease?

Niemann-Pick type C disease (NP-C) is an inherited, autosomal, recessive disease, which means that the gene carrying the mutation is located on one identical pair of the 22 pairs of chromosomes (autosomes) that every person has. Someone with a mutated gene on one chromosome and a normal gene on the other will not have NP-C, but will be an NP-C carrier. This means that although they are perfectly healthy, they can pass the disease onto their children. Two copies of the mutated gene, one inherited from the mother and the other from the father, must be passed on for a child to inherit NP-C. It is only when both parents carry the same recessive gene mutation that there is a chance of a child being born with NP-C. Consequently, for each pregnancy involving two NP-C carriers, there is a 1 in 4 chance of having a child that will neither be a NP-C carrier nor have NP-C, a 1 in 2 chance of having a child that will be a NP-C carrier and a 1 in 4 chance of having a child with NP-C (Figure 1).¹

References

1. Wraith JE, Imrie J. Understanding Niemann-Pick disease type C and its potential treatment. UK Blackwell Publishing, 2007.