Stargardt’s Disease Genetic Information Page
Stargardt’s disease is also sometimes called fundus flavimaculatus, Stargardt’s macular dystrophy, juvenile macular degeneration and STGD.
The diagnosis of Stargardt’s disease often requires a number of tests and examinations. These include an Ophthalmologist examining the back of the eyes, visual acuity, visual field and colour vision tests. Different methods are used to take images of the retina including fundus autofluorescence (FAF) to see the structure of the retina and optical coherence tomography (OCT) which looks at the layers of the retina. An electroretinogram (ERG) assesses retinal function.
Genetic testing can also now help to clarify the diagnosis, although testing does not yet identify the genetic cause of the condition in all cases (2017).
Children with Stargardt’s disease should have an annual review by an Ophthalmologist. Adults with the condition are often discharged as there is no treatment, but seeing an Ophthalmologist about every 5 years for a general check-up and update on what is known about the condition is reasonable. Regular general eye checks with an optician are advisable for everyone, including people with Stargardt’s.
Management is focussed on maximising existing vision using aids and techniques. Low Vision clinics can provide optical aids, such as, magnifiers and monoculars. Many people with Stargardt’s read large bold print. Assistive technology including electronic magnifiers and magnification and text to speech computer software can also be helpful.
Social services can offer certain home adaptations and practical mobility training.
Some evidence suggests that people with Stargardt’s should avoid taking extra vitamin A in supplements. Wearing UV blocking sunglasses outdoors is also recommended.
GENETICS AND INHERITANCE
The most common form of Stargardt’s disease, Stargardt 1 (STGD1), is caused by genetic changes (mutations) in a gene called ABCA4 on chromosome 1. This gene provides the instruction for an adenosine triphosphate (ATP)-binding cassette transporter found in the light-sensing (photoreceptor) cells of the retina. Genetic changes in the ABCA4 gene cause defects in the function of this transporter resulting in the accumulation of toxic waste products (lipofuscin pigments) which over time cause retinal cell death.
Stargardt 1 is passed on in families in an autosomal recessive pattern. This means that someone with the condition will have two changed copies of the ABCA4 gene. They will have inherited one changed copy from their mother and the other from their father. Someone with one changed and one working copy of the ABCA4 gene is a carrier of Stargardt 1. Carriers do not have symptoms of the condition.
Each full sibling of someone with Stargardt 1 has a 1 in 4 or 25% chance of inheriting the condition. This chance is the same for males and females.
When someone with Stargardt 1 has children with an unrelated partner, the chance of a child inheriting the condition is about 1 in 100 or 1%.
Less commonly people can have a disorder that looks like Stargardt’s but it is due to a different gene. Other known genes include the ELOVL4 gene (causing STGD3), PROM1 gene (causing STGD4) and RDS gene (also known as PRPH2). The disorder originally suggested to be STGD2 was subsequently found to be caused by the same gene as STGD3.
Stargardt’s caused by changes in the ELOVL4, PROM1 and RDS genes is inherited in an autosomal dominant pattern, which is different from that described above. For more information on dominant inheritance visit: http://www.geneticdisordersuk.org/aboutgeneticdisorders/inheritance#dominant
GENETIC SERVICES AND TESTING
Genetic testing methods change over time. A genetic professional from an NHS genetic clinic (http://www.geneticdisordersuk.org/parentsofaffectedchildren/managinghealthcare/specialistgeneticcentres) can arrange genetic testing, where needed, and review the inheritance pattern. Families are welcome to seek advice from genetic clinics at various times of life. For example, when an individual with Stargardt’s disease or their siblings want more details as they get older, they could ask about the condition for themselves.
For further information and support for Stargardt’s disease you can also visit:
The Macular Societyhttps://www.macularsociety.org/
Helpline: 0300 3030 111
RP Fighting Blindness https://www.rpfightingblindness.org.uk/
Helpline: 0845 123 2354,
Stargardt’s UK Facebook group: https://www.facebook.com/groups/318029081640409/
Many thanks to Emily Clarke, a registered Genetic Counsellor at Genetic Disorders U.K. who has written this page.