Genes are the blueprint for our bodies. If a gene contains a change (called a mutation), it disrupts the gene message. Those with albinism have a mutation on a gene influencing the production or development of pigment in the eye (and perhaps also in the hair and skin). While there are 21 (or more) different genes causing albinism, for the purpose of this discussion we will refer to them collectively as albinism genes.
Genetics of Albinism
The mutated genes causing ALBINISM are generally autosomal recessive genes, although one type is an X linked gene which behaves differently in men.
Autosomal – a “non sex” chromosome (ie not linked to the X or Y chromosome)
Recessive – only appears if two copies of the same gene are present
Albinism results when two mutated copies of genes (albinism genes) are received at conception, combining as a pair (one from the mother and one from the father).
When both parents are carriers
When both parents are carriers of the albinism gene there are different ways the condition could present.
With each pregnancy there is a one in four (25%) chance of a child inheriting the two albinism genes and having albinism, a two in four (50%) chance of the child receiving one albinism gene and one unchanged gene, resulting in them being a carrier of the albinism gene, and a one in four (25%) chance of not carrying the albinism gene at all.
Like the roll of a dice, using a family of four children as an example, all four children could present with albinism, none could, one could or some could. Each pregnancy has the chances anew.
When one parent has albinism and the other is a carrier
When one parent has albinism and the other is a carrier (has one copy of the albinism gene), each pregnancy has a two in four (50%) chance of the child having albinism, and a two in four (50%) chance of the child being a carrier.
When both parents have albinism
If both parents have albinism, all children will generally have albinism, although they may present with a different form of albinism, depending on the gene/s affected and how they are paired.
When only one parent carries the albinism gene
When only one parent has the albinism gene, whether as a carrier or presenting with albinism, the partner’s matching non-albinism gene in the pair will dominate and generally none of the children will have albinism, although they may be carriers with no symptoms (a two in four (50%) chance with each pregnancy).
Why is there often no history of albinism in the family?
If only one parent has the albinism gene, it can be carried for generations without it “appearing” – it is in “carrier” state, or in other familial branches. When a child with albinism is born, both sides of the family commonly say “it’s not from our side” – it is definitely from both sides, you just may not have seen or heard of it. Smaller families can also “hide” the condition, as albinism may be passed at carrier level to children and those children’s children, to then present in later families.
Official Albinism genes
At the beginning of 2020 there were officially 19 albinism genes: TYR, OCA2, TYRP1, SLC45A2, SLC24A5, LRMDA, GPR143, HPS1, AP3B1, HPS3, HPS4, HPS5, HPS6, DTNBP1, BLOC1S3, BLOC1S6, APB3D1, LYST and SL38A8. All of these 19 genes have a recessive behaviour apart from GPR143 which is X-linked and therefore behaves differently in men.
Mid 2020 there are now 21 known albinism genes as two new genes were discovered – one in the OCA group and one in the HPS group. Research has also identified several other non albinism genes that when combined with an albinism gene, may result in albinism.
We are working with professionals in other organisations in order to bring you the latest accurate information, where we hope to accurately demonstrate how the albinism genes work in the previously known types of albinism.
Genetic Testing
An ophthalmologist is able to make a clinical diagnosis of albinism by looking at the structures inside the eye, supported by a range of vision tests. While they may make a clinical judgment about an OCA or OA diagnosis based on skin and hair colouring, only genetic testing can accurately determine the exact type of albinism present – a genetic diagnosis.
While researchers have found the mutations that cause albinism, these changes are not always in exactly the same place, even for a given type of albinism.
Should I undergo genetic testing?
This is a personal decision to a point. With genetic testing in Australia being so limited, you would potentially be facing a high cost and long delay in receiving results, as tests are sent overseas to be conducted in full.
If there are associated excessive bruising, bleeding, breathing or irritable bowel (IBS) type symptoms, there is a possibility of HPS, and this can only be discovered thorough genetic testing. Those with HPS recommend all people with OCA or inconclusive OCA be tested; again this would involve overseas testing, but if HPS is suspected, is a worthy reason for testing.
Those who have not been able to receive a definite clinical diagnosis of albinism may also benefit from genetic testing, in order to receive a diagnosis that will be accepted by NDIS. Where an ophthalmologist states albinism is suspected due to partial changes in the retina (and perhaps pigment in hair and skin), the person may not be recognised as having a recognised disability, and therefore deemed not eligible for the NDIS.
With research discovering so much, the potential for albinism related genetic data leading to further discoveries is high. Added to this, future genetic testing may find other links, more mutations and variants, and may even be used for cross research (as in linking results with those from other conditions) and much more.
Undergoing testing for a particular type of albinism will change the outcome very little (unless you have HPS symptoms), but it does give albinism research another piece of information which is stored at your ophthalmologist’s office; potentially one day being used to create an Australian research database.
Genetic Testing in Australia
In order to access genetic testing, patients will need to be referred (from a GP or Ophthalmologist) to a clinical genetics service for consultation with a genetics doctor and/or genetic counsellor who will advise what testing (if any) is suitable. There are a number of different genetics services available depending on where individuals live and whether they are an adult or child. Appointments with these services are free of charge, however testing is not generally covered by Medicare.
The following are services that are known to conduct tests for albinism, however the AFA does not make recommendations. The following information has been provided by each facility early in 2020 – we welcome any information that can be added to this section. Many services send some samples to overseas laboratories for testing, resulting in additional expense or delay in reporting of results.
Victoria
The Victorian Clinical Genetics Service (VCGS) offer tests for Ocular and Oculocutaneous Albinism and (in 2019) looks at 18 genes, via technology known as exome sequencing. For these tests you require a referral from your doctor to the local Genetics Service, the Clinical Geneticist there will then make the request to the VCGS for testing. The cost is a bit more than $1000 (current in 2019) and there is no subsidised funding by Medicare or other means for this test. Go to the website for more information https://www.vcgs.org.au/tests/clinical-exomes
For children, the best pathway is a referral to VCGS – Ophthalmology at the Royal Children’s Hospital should be able to refer them. For adults who are not pregnant, referral to their nearest adult genetics service is the best option.
If a female member is pregnant, then referral should go to a prenatal genetic service.
Queensland
Genomics for Life in Queensland does some genetic testing for albinism. As of 2019, they are able to offer testing of the genes GPR143, OCA2, TYR associated with Oculocutaneous Albinism Type 1, Oculocutaneous Albinism Type 2 and X-Linked Ocular Albinism. Other types of albinism, including HPS, are not covered. All of their testing is conducted in house, at their laboratory in Brisbane.
More information to come
We are currently following the latest research into the genetics of albinism and the testing available in Australia. We will notify members of any updates to this page.
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