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Condition report · Ophthalmological

GPR143-Related Foveal Hypoplasia (Ocular Albinism Type 1)

Whole genome sequencing reads the GPR143 gene on the X chromosome for changes that cause foveal hypoplasia, mainly in males, with reduced vision and involuntary eye movements.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

An inherited eye condition, mainly affecting males, in which the central retina (fovea) does not fully develop, causing reduced vision and involuntary eye movements. It is caused by changes in the GPR143 gene on the X chromosome.

This is an inherited eye condition, mainly affecting males, in which the centre of the retina, called the fovea, does not fully develop. It causes reduced vision from infancy and nystagmus, meaning involuntary eye movements. Many males also have less pigment in the iris and retina, and eyes that do not point in the same direction.

The condition is caused by changes in GPR143, which makes a receptor in the pigment cells of the eye that controls the growth of pigment granules. Because the gene is on the X chromosome, males with one changed copy are affected, while females are usually carriers.

The vision loss is permanent but usually does not get worse. Care involves glasses, low-vision aids, sunglasses for light sensitivity and educational support. Genetic counselling explains X-linked inheritance, and carrier testing is available for female relatives.

An affected male passes the change to all of his daughters and to none of his sons. Carrier women have a 50% chance of passing it to each child, so sons of carrier women have a 50% chance of being affected.

The condition we analyse

GPR143-Related Foveal Hypoplasia

X-linked recessive

Caused by changes in GPR143, which makes a receptor in pigment cells of the eye that controls pigment granule growth. Because the gene is on the X chromosome, males with one changed copy are affected, while females are usually carriers.

Signs and symptoms

Reduced visual acuity from infancy and nystagmus (involuntary eye movements), with an underdeveloped fovea. Many males also have reduced pigment in the iris and retina, misrouted optic nerve fibres and strabismus, while skin and hair colour are usually normal. Carrier females usually have normal vision but may show a mottled pattern of retinal pigment.

What a diagnosis changes

Regular eye care with glasses, low-vision aids and educational support; sunglasses can help with light sensitivity. Genetic counselling explains X-linked inheritance: sons of carrier women have a 50% chance of being affected, and carrier testing is available for female relatives.

Genes analysed

Also known as

GPR143-related foveal hypoplasia with or without albinism

Includes 2 related subtypes ↓
  • nystagmus 6, congenital, X-linked
  • X-linked recessive ocular albinism
MONDO:0700230Sources: [1][2][3]

Why whole genome sequencing

This X-linked condition mainly affects males, so the family pattern matters when advising female relatives. Whole genome sequencing reads the GPR143 gene in the same test.

Sons and daughters of carriers

Carrier women have a 50% chance of passing the change to each child, and males who inherit it are affected. Carrier testing is most informative once the family's GPR143 change has been identified.

A negative result is not conclusive

Genetic testing finds a GPR143 change in more than 9 in 10 affected males, so a negative result does not completely rule out the condition. The diagnosis also rests on clinical eye findings such as nystagmus and foveal hypoplasia, so a negative result should be read alongside them.

Limitations

  • Genetic testing finds a GPR143 change in more than 9 in 10 affected males, so a negative result does not completely rule out the condition.

References

  1. Lewis RA, 2004. Ocular Albinism, X-Linked – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY. GeneReviews
  2. Ocular albinism. MedlinePlus Genetics
  3. GPR143 gene. MedlinePlus Genetics

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