Choroideremia- A Rare Genetic Disorder

Introduction:

Choroideremia is a condition that primarily affects men and is characterized by progressive vision loss. Night blindness, a condition that can start in early childhood, is typically the first sign of this condition.

What Is Choroideremia?

Choroideremia is a rare genetic condition that impacts the eyes. It deteriorates vision, which eventually results in blindness. It is a serious condition that affects men as it is an X-linked inherited condition. Night blindness, a condition that starts in early childhood, is the first sign of this condition. The other signs that are present are tunnel vision (decrease in the field of vision) and visual acuity (ability to visualize the details decreases). The vision problems encountered in choroideremia are due to atrophy of the cells of the specialized light-sensitive tissue that lines the back of the eye (retina) and a nearby network of blood vessels (the choroid). The progression of choroideremia-related vision impairment varies among those who are affected, but it worsens over time. However, everyone who has this condition will eventually go blind, usually in their late 20s or early 30s.

Photoreceptor cells in the retina of the eye are responsible for capturing light and converting it into electrical signals. The optic nerve carries these signals to the brain, where they are transformed into images. The white protective layer between the retina and sclera that covers the eye is a layer called the choroid.

What Are the Clinical Manifestations of Choroideremia?

• Night Blindness- Difficulty in seeing at night is the first sign and usually occurs before ten years of age.

• Difficulty inside (peripheral) vision, which eventually results in vision loss.

• Inability to see the colors.

• Lack of sharpness in the vision.

• Despite the fact that carrier females typically exhibit no symptoms, chorioretinal degeneration signs can be consistently seen.

How Is Choroideremia Inherited?

Choroideremia has an X-linked recessive inheritance pattern. The gene responsible for choroideremia is present on the X chromosome, which is one of the two sex chromosomes. One altered copy of the gene in each cell is sufficient to cause the condition in males (who have only one X chromosome). A mutation must exist in both copies of the gene in females (who have two X chromosomes) for it to result in the disorder. X-linked recessive disorders affect men much more frequently than they do women. Fathers are unable to pass on X-linked traits to their sons, which is a trait of X-linked inheritance.

A female who has one mutated copy of the gene in each cell is referred to as a carrier in X-linked recessive inheritance. In spite of not showing symptoms of the disorder, she can pass on the altered gene. During a comprehensive eye exam, it is possible to spot small areas of retinal cell loss in females who have choroideremia. Later in life, these changes can hinder vision.

How Is Choroideremia Diagnosed?

It is crucial to get an eye examination regularly. In case a patient complains of any symptoms, an eye doctor will check the eyes immediately. Below is the list of tests performed if a patient is suspected of choroideremia.

• Clinical Findings-

  • Defective Dark Adaptation- Poor night vision is frequently the first symptom in affected males, usually as a preteen.

  • Fundus Appearance- The mid-periphery of the fundus is where patchy areas of chorioretinal degeneration typically start to appear. The deep choroidal vessels are preserved as the chorioretinal degeneration progresses to a marked loss of the retinal pigment epithelium and choriocapillaris (the inner of the two vascular layers of the choroid that is primarily made up of capillaries).

• Diagnostic Methods-

  • Electroretinogram- This examination measures how the retina reacts to light. Electroencephalogram disks will be applied to the face, eyes, head, and scalp by a healthcare professional, who will then place a pair of incredibly thin wires over the front of each eye, just above the lower eyelid. To evaluate the activity of the retina, the technician will shine bright lights in front of the eyes.

  • Optical Coherence Tomography (OCT)- It is a non-invasive examination technique that creates images of the back portion of the eye, which is the retina using reflected light.

  • Fluorescein Angiography- It is a technique to examine the blood vessels of the eye. A dye is injected into the veins so that the blood vessels become visible.

  • Genetic Testing- A DNA test, also known as genetic testing, can reveal gene mutations. The blood, hair, skin, tissue, or amniotic fluid can all be used as samples in a lab. Choroideremia and retinitis pigmentosa can be distinguished through genetic testing.

What Is the Treatment of Choroideremia?

Providers are unable to treat choroideremia. However, a patient may be treated for other problems. In a patient with choroideremia, treatment for the clinical manifestations is provided by healthcare workers. Devices like magnifiers and genetic and mental health counseling are just a few examples of coping strategies.

• The problem of retinal detachment, which is more common in people with high myopia and is also seen in patients with choroideremia, is handled by an ophthalmologist using standard surgical methods.

• For patients who have a posterior subcapsular cataract, cataract surgery may be necessary.

• When a person suffering from choroideremia is outside, UV-blocking sunglasses should be used. It offers some protection to the eyes.

• Bevacizumab administered intravitreally (through the eyes) may be used to treat a few rare cases of choroidal neovascularization.

• Treatment utilizing the remaining vision left in a patient is provided by specialists of low vision (optometrists). This treatment benefits patients who are unable to perform various functions due to low vision or vision impairment. Optometrists decide the treatment plan based on age and the needs of the patient.

• Counseling from organizations or specialists who assist the blind and visually impaired may be able to help the affected person deal with problems like depression, losing their independence, driving, and anxiety over work-related issues.

Conclusion:

Patients with choroideremia can typically anticipate that their peripheral (side) vision will deteriorate over time, leaving them with only their central vision. The condition could eventually lead to blindness. So many emotions can arise in a patient from having a condition for which there is no known treatment. Management of the disease is based on treating the symptoms, as there is no cure for this genetic disorder. However, having a good working relationship with the medical team can be beneficial. Research is currently being done to find cures and treatments for genetic diseases like choroideremia. With a positive approach and proper counseling, patients are able to lead a better life.