What Is Nijmegen Breakage Syndrome?
Nijmegen Breakage Syndrome (NBS), caused by mutations in the NBN gene, is an inherited disease in which the body's DNA is prone to breakages. The NBN gene is responsible for the nibrin protein which is involved in DNA repair and the promotion of chromosome stability. Dysfunction of the nibrin protein causes individuals with NBS to develop cancer at an early age and experience frequent lung and sinus infections.
Infants with NBS are often born with small head size. Their physical growth is often slow, leaving them smaller than average for their age. They have characteristic features, including a sloping forehead, small chin, big ears, and a prominent nose, which become more apparent later in childhood.
In one study, 35% of the 70 people studied who had NBS developed cancer, most commonly a type known as B-cell lymphoma, between the ages of 1 and 34. Individuals with NBS cannot tolerate the high doses of ionizing radiation often used to treat cancer and must find alternate treatment methods such as chemotherapy.
Individuals with NBS have a reduced immune response and experience frequent infections in the lungs, ears, sinuses, and urinary tract. Recurrent pneumonia or bronchitis in those affected by NBS can be life-threatening. Patients' intellect appears to develop normally or near-normally in early childhood but typically declines until the patient reaches mild-to-moderate levels of intellectual disability around the age of 10.
Carriers of NBS do not show symptoms of the disease. However, recent studies have shown that some carriers may have a greater-than-average risk of developing cancers, including but not limited to non-Hodgkin lymphoma, breast cancer, and prostate cancer. Breast-cancer screening recommendations for female carriers include mammography and possible breast MRI starting at age 40.
How Common Is Nijmegen Breakage Syndrome?
The prevalence of NBS is estimated to be 1 in 100,000 births, but there is currently insufficient population-specific prevalence information. The disease is most common in individuals of Eastern European or Slavic background, specifically those from Poland, the Czech Republic, and Ukraine.
How Is Nijmegen Breakage Syndrome Treated?
There is no treatment to address the underlying cause of NBS, but specific symptoms can be treated. Supplements such as Vitamin E and folic acid may be helpful, and in some individuals, intravenous infusions with immunoglobulin or preventative antibiotics can be used to reduce infections. Special education and speech therapy can also be considered to address delays in development. Hormone replacement therapy may be useful for female sexual development, but most women with NBS are not fertile. Stem-cell transplantation may also be considered for treatment of NBS.
Large doses of radiation must be avoided in individuals with NBS, even before birth. Individuals with NBS should be monitored for proper growth and development, delayed onset of puberty, and early cancer signs.
What Is the Prognosis for an Individual with Nijmegen Breakage Syndrome?
Some individuals with NBS do live into adulthood, though typically the lifespan does not extend beyond one's thirties or forties. The longest known lifespan of an individual with NBS is 53. Cancer is the most common cause of death among individuals with NBS, followed by lung infections leading to respiratory failure.