What are the other Names for this Condition? (Also known as/Synonyms)
- Atrophia Bulborum Hereditaria
- Fetal Iritis Syndrome
- Whitnall-Norman Syndrome
What is Norrie Disease? (Definition/Background Information)
- Norrie Disease (ND) is an X-linked inherited disorder characterized by significantly reduced vision and hearing (which may manifest as blindness and deafness), along with cognitive and/or behavioral problems in some individuals
- Norrie Disease affects males almost exclusively and symptoms are generally apparent at birth. The risk factors include genetic abnormalities in the NDP gene that is typically observed, if there is a family history of the condition
- The disorder is caused by an inherited genetic mutation affecting the NDP gene on the X-chromosome, which controls production of the protein ‘norrin’
- The signs and symptoms may include retinal degeneration, eye opacity, increased eye pressure, underdeveloped iris, progressive hearing loss, cognitive developmental delays, behavioral problems, endocrine dysfunction, and even severe mental retardation
- A diagnosis of Norrie Disease includes a thorough physical examination and evaluation of the patient’s medical history, and genetic tests for families and individuals suspected of carrying the defective gene
- Complications include progressively worsening pain in the eye due to increased intraocular pressure, behavioral problems, aggressive behavior, cognitive regression, and decreased quality of life
- The treatment for Norrie Disease includes eye surgery, use of hearing aids, special education, and counseling for families with a member affected by the condition
- In many cases, the prognosis is good as individuals lead fulfilling lives, with adequate treatment. However, the prognosis also depends upon the severity of the symptoms of Norrie Disease
Who gets Norrie Disease? (Age and Sex Distribution)
- Children with Norrie Disease display most symptoms at birth or shortly after birth
- The disorder almost only affects males, although females can be affected as well
- All races and ethnic groups can be affected and no specific predilection is observed
What are the Risk Factors for Norrie Disease? (Predisposing Factors)
The risk factors for Norrie Disease may include:
- Having a positive family history of the disorder
- In some cases, the affected individual’s mother may also have experienced vision loss
It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.
Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.
What are the Causes of Norrie Disease? (Etiology)
Norrie Disease may be caused by an inherited genetic mutation affecting the NDP gene on the X-chromosome.
- This gene holds the blueprints for making certain proteins, known as norrin, which is believed to play a part in the formation of blood vessels, especially those which supply blood to parts of the eye and ear
- Severe cases can arise from a deletion of large areas of the NDP gene
- Though it is X-linked, females who inherit only one copy of the defective gene may sometimes experience symptoms of the disorder
What are the Signs and Symptoms of Norrie Disease?
The signs and symptoms of Norrie Disease may include the following:
- Degeneration of the retina during fetal development, which can leave the child blind from birth
- The retina is responsible for converting light signals to nerve impulses to be relayed to the brain
- The retinas separate from their supporting tissue, which can create a small, gray-yellow mass to form in the back of the eye that may be mistaken for a tumor
- This can also cause the pupil to appear whitish, a condition referred to as leukocoria
- The front of the eye may later increase in opacity (cataract), which will worsen with age
- Shrinking of the eyeballs over time, which may also appear small at birth (microphthalmia)
- Dilated pupils
- Increased eye pressure, which can be painful due to occluded ocular tracts leading out of the eyeball
- Underdeveloped iris (colored portion of the eye) that may stick to the lens (anterior synechiae) or the cornea (posterior synechiae)
- Progressive hearing loss due to abnormalities in blood flow to the cochlea (structure of the inner ear), which can vary greatly from one to another, depending on the individual’s specific condition
- Cognitive developmental delays beyond what is expected in conjunction with blindness may be present
- Behavioral problems including psychosis, aggressive behavior, and cognitive regression
- Some individuals with Norrie Disease may experience dementia later in life
- Venous stasis ulcers (improperly functioning venous valves, especially of the legs)
In severe cases (NDP deletion), affected individuals may experience seizures, growth failure, endocrine dysfunction, and severe mental retardation.
How is Norrie Disease Diagnosed?
A diagnosis of Norrie Disease may include the following tests and exams:
- A careful physical examination and evaluation of the patient’s medical history
- Examination of characteristic findings (signs and symptoms)
- Assessment of a family history of the disorder
- Vision testing
- Testing for hearing abilities
- Genetic testing to help identify the defective NDP gene
Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.
What are the possible Complications of Norrie Disease?
The possible complications associated with Norrie Disease may include:
- Progressively worsening pain in the eye due to increased intraocular pressure
- Behavioral issues including psychosis, aggressive behavior, and cognitive regression
- Decreased quality of life
How is Norrie Disease Treated?
Treatments for Norrie Disease may involve groups of physicians working in coordination to help propose specific treatments, which may include:
- Eye surgeries to remove cataracts and reattach retinas
- In utero vitrectomy (removal of the vitreous humor from the eye) may help reduce vision loss
- Use of hearing aids or cochlear implants in case of severe hearing difficulties, typically as the individual nears adulthood
- Specialized education so that children can reach their maximum potential
- Genetic counseling for families with a family history of the Norrie Disease
How can Norrie Disease be Prevented?
Norrie Disease is a genetic disorder, and currently, there are no methods or guidelines available to prevent its occurrence.
- Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
- If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
- Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Norrie Disease
What is the Prognosis of Norrie Disease? (Outcomes/Resolutions)
The prognosis for Norrie Disease is generally good.
- With proper medical attention and therapy, many individuals can live long, fulfilling lives
- In some cases, the characteristic symptoms associated with Norrie Disease (such as blindness and deafness), may present serious challenges for caregivers and the affected individuals
Additional and Relevant Useful Information for Norrie Disease:
The disorder was first characterized by the Danish ophthalmologist Gordon Norrie in 1927.