Norrie Disease

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Boys with ND are typically completely blind, with no light perception, in both eyes (bilateral) from birth (congenital). Some are born with a small amount of vision which usually deteriorates shortly after birth leaving a few with a little residual vision.

The visual problems are a result of incomplete formation of the eyes during a baby’s development in the womb. The retina, which is the thin layer of light sensitive cells at the back of the eye, is disorganised and separates from it’s underlying supporting tissue (retinal detachment). This results in the development of greyish yellow fibrovascular masses in the back of the eyes which can cause the pupils to appear white.

As the eyes age through childhood and adolescence, secondary issues emerge. These include eye shrinkage, clouding of the lens of the eye (cataracts), and degeneration of the coloured part of the eye (iris atrophy).

In addition to the eye problems, the symptoms of ND include hearing loss which slowly gets worse over many years. This often starts in childhood but may not develop until adulthood.

Some (approximately 30%-50%) boys with ND have developmental delay, learning disability or behavioural issues.

In some cases ND has been associated with peripheral venous insufficiency where the flow of blood through the veins is inadequate, causing blood to pool in the legs. Varicose veins and leg ulcers can develop.

Individuals with the condition can also have low muscle tone and compromised immune systems.

Around 20 cases in the UK are known and up to 800 globally. However, the Norrie Community feel there are probably many more people with Norrie who have not been diagnosed.

Contact other families affected by Norrie Disease

Diagnosis

ND is most often initially diagnosed on the basis of clinical findings, if the individual presents with congenital blindness. Clinical genetic testing is available to help confirm the diagnosis.

Treatment

The treatment of ND is directed towards the specific symptoms that are apparent in each individual. Treatment is likely to require the coordinated efforts of a team of specialists:

Ophthalmologists - this could include removal of cataracts, treatment for glaucoma, laser treatment, shells for the eyes (for structural and cosmetic purposes) or prosthesis. Those who have not completely lost their vision have been treated with surgery or laser therapy in infancy in the US.

Audiologists - regular hearing tests and hearing aids or cochlear implants.

Speech and language therapists.

Occupational Therapists.

Physiotherapists.

Rehabilitation Officer for sensory impairment.

Qualified Teacher of the Visually Impaired.

Endocrinologist.

Rheumatologist.

Paediatrician.

Other healthcare professionals may also be needed to systematically and comprehensively plan the treatment and management of the condition on a case by case basis.

Research

Norrie research and studies can be found on the Norrie Disease Association website http://www.norriedisease.org/

The Norrie Community are looking at securing further research into Norrie and the secondary effects of Norrie, for example, the hearing loss.

Genetics and Inheritance

ND is caused by a genetic misprint (mutation) in the ND pseudoglioma (NDP) gene which is located on the X chromosome. ND is passed on in families in an X-linked recessive pattern of inheritance.

Females (XX) have two copies of the NDP gene, one on each of their two X chromosomes. Males (XY) have only one copy on their single X chromosome. ND occurs in males when there is a misprint in their single copy of the NDP gene. Otherwise healthy females can carry an altered NDP gene with the working copy on their other X chromosome usually being enough to compensate for this, preventing them from developing the condition.  Women who are carriers of ND have a 1 in2 (50%) chance of passing the condition on to each son they have. Each of their daughters has a 1 in 2 (50%) chance of being a carrier of the condition.  When a man with ND has children he will pass on his X chromosome to all his daughters and so all (100%) daughters will be carriers of ND. None of the sons of a father with ND will inherit the condition from him as they will get their single X chromosome from their mother.

The vast majority of mothers of a boy with ND are carriers of the condition. Very occasionally ND can occur due to a new spontaneous (de novo) mutation, without the mother actually being a carrier of the condition. If the mother has had carrier testing for ND and has NOT been found to be a carrier then the chance of her having another child with a Norrie gene alteration is low but still slightly higher than that of the general population. This is because of the very small possibility of there being a few egg cells in her ovaries that have a Norrie gene alteration (a situation known as germline mosaicism).

Genetic Services and Testing

Genetic testing methods change over time. A genetic doctor from an NHS genetic clinic (http://www.bsgm.org.uk/information-education/genetics-centres/) can arrange testing of the NDP gene where appropriate, review the inheritance pattern and provide up-to-date management advice. Families are welcome to seek advice at various times of life from the genetic service or paediatrician. For example, when a child growing up with ND or their siblings want more details, they could attend the genetic clinic to ask about the condition for themselves.

Contact other families affected by Norrie Disease

We will try to put you in touch with other families affected by Norrie Disease. Fill in the form below and a member of our support team will get back to you within 7 working days.

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