Nijmegen Breakage Syndrome

What Your Test Results Mean:

Carriers typically show no symptoms of Nijmegen breakage syndrome; however, carriers are at an increased risk of having a child with Nijmegen breakage syndrome. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

Nijmegen breakage syndrome is an inherited condition characterized by short stature, an unusually small head size, distinctive facial features, an increased risk of cancer, and immunodeficiency. The symptoms of the disorder are caused by a non-functional protein, nibrin. Nibrin is normally responsible for repairing damaged DNA in a person’s cells, and when it is non-functional, the cells accumulate genetic damage. Because people with Nijmegen breakage syndrome have impaired immune function, they are very susceptible to recurrent infections, especially of the respiratory tract. These individuals also develop mild to moderate intellectual disability, and most affected women have premature ovarian failure. Most individuals with Nijmegen breakage syndrome develop cancer, usually in childhood or adolescence, and thus have reduced longevity. Treatment is symptomatic.

How the Genetics Works:

The clinical features of Nijmegen breakage syndrome can be explained by pathogenic variants in the NBN gene. In general, individuals have two copies of the NBN gene. Carriers of Nijmegen breakage syndrome have a single variant in one copy of the NBN gene while individuals with Nijmegen breakage syndrome have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.

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