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Genetics

Of the nine forms of NBIA currently identified, all but two are recessive. Because most of our genes exist in pairs (one from the mother and one from the father), we normally carry two working copies of each gene. When one copy of a recessive gene has a change (mutation) in it, the person should still have normal health. That person is called a carrier. Recessive diseases only occur when both parents are carriers for the same condition and then pass their changed genes on to their child.

Statistically, the chances are one in four that two carriers would have an affected child, two in four that they would have a child who is also a carrier and one in four that they would have a child without the genetic mutation.

Neuroferritinopathy is a dominant condition. In this case, a person affected with neuroferritinopathy has one working copy of the gene and one copy that has a change, or mutation. This single mutation is enough to cause the disease. There is a one in two chance, or 50 percent, that an affected individual will pass the gene change on to any of his or her children. For neuroferritinopathy, most affected individuals have one parent who is also affected.

Beta-propeller Protein-Associated Neurodegeneration (BPAN) is thought to occur de novo, meaning there is an alteration in a gene that is new in the affected individual and was not inherited from either parent. This can happen in a germ cell (egg or sperm) from one of the parents or in the fertilized egg itself.  In the case of BPAN, the gene sits on the X chromosome, one of the two chromosomes that determine sex.

Affected Population: Overall, NBIA affects males and females in equal numbers (BPAN occurs more frequently in females). The frequency of NBIA in the general population is estimated between 1-3/1,000,000 individuals. Because rare disorders like NBIA often go unrecognized, these disorders may be underdiagnosed or misdiagnosed, making it difficult to determine the accuracy of these estimates.