What is Choroideremia? Causes and Treatments

Written by Medicover Team and Medically Reviewed by Dr Manaswini Priya Varanasi , Ophthalmologists

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1. Causes 2. Find a Doctor 3. Diagnosis 4. Treatment 5. FAQs

Choroideremia is a rare, progressive genetic disorder that primarily affects males, leading to degeneration of the choroid, retinal pigment epithelium (RPE), and photoreceptors in the eye. This degenerative condition results in progressive vision loss and may eventually lead to blindness. Understanding its causes, symptoms, diagnosis, and treatment options is essential for effective management and vision preservation.

What are the Causes of Choroideremia?

Genetic Factors

Choroideremia is inherited in an X-linked recessive pattern, meaning the defective gene is located on the X chromosome. Since males have only one X chromosome, a single abnormal gene is enough to cause the disorder. Females usually act as carriers because they have two X chromosomes, although some carriers may develop mild symptoms.

The condition is caused by mutations in the CHM gene, which produces Rab Escort Protein-1 (REP-1). This protein is essential for the normal transport of materials within retinal cells. Mutations in the CHM gene result in a deficiency or absence of REP-1, leading to progressive degeneration of retinal cells.

Pathophysiology

The lack of functional REP-1 protein causes abnormal intracellular transport due to the accumulation of unprenylated Rab proteins. This defect particularly affects retinal pigment epithelial cells and photoreceptors, resulting in their gradual degeneration and the progressive vision loss characteristic of choroideremia.

What are the Symptoms of Choroideremia?

Early Symptoms

The earliest signs of choroideremia usually appear during childhood or adolescence. Night blindness (nyctalopia) is often the first symptom because rod photoreceptors, responsible for vision in low-light conditions, are affected early in the disease.

Progressive Vision Loss

As the disease advances, peripheral vision gradually narrows, resulting in tunnel vision. This occurs because of the progressive degeneration of peripheral retinal cells and the choroid. Over time, central vision may also become affected, making activities such as reading and recognizing faces increasingly difficult.

Advanced Stage

In advanced stages, degeneration extends to the macula, the central portion of the retina responsible for detailed vision. This can result in severe central vision loss and significant impairment of daily activities.

When to See a Doctor for Choroideremia?

If you or your child develops symptoms suggestive of choroideremia, consult an Ophthalmologist promptly. Early diagnosis and regular monitoring can help preserve vision, identify complications, and provide access to genetic counseling and emerging treatment options.

If you experience difficulty seeing in dim light or notice worsening night vision.
If you develop gradual loss of peripheral (side) vision or tunnel vision.
If you notice progressive blurred vision or difficulty performing daily visual tasks.
If you have a family history of choroideremia or other inherited retinal disorders and develop vision changes.
If routine eye examinations reveal retinal or choroidal degeneration.
If you experience unexplained vision loss in one or both eyes.
If genetic testing suggests a mutation associated with choroideremia.
If your symptoms persist or worsen, consult an Ophthalmologist promptly for a comprehensive eye examination, retinal imaging, genetic evaluation, and appropriate management.

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How is Choroideremia Diagnosed?

Clinical Examination

A comprehensive eye examination is the first step in diagnosing choroideremia. Ophthalmologists evaluate for characteristic retinal changes such as:

Peripheral chorioretinal atrophy
Pigmentary changes in the retina
Attenuation of retinal blood vessels

Genetic Testing

Genetic testing confirms the diagnosis by identifying mutations in the CHM gene. Genetic counseling is recommended for affected individuals and their families to understand inheritance patterns and future reproductive risks.

Imaging Techniques

Advanced imaging methods such as optical coherence tomography (OCT) and fundus autofluorescence (FAF) help assess retinal and choroidal damage, monitor disease progression, and evaluate the effectiveness of potential treatments.

What are the Treatment Options for Choroideremia?

Current Treatments

Currently, there is no cure for choroideremia. However, several treatment strategies are being investigated to slow disease progression and preserve vision for as long as possible.

Gene Therapy

Gene therapy is one of the most promising treatment approaches for choroideremia. This technique delivers a functional copy of the CHM gene to retinal cells using viral vectors. Early clinical trials have shown encouraging results, with some patients experiencing stabilization or improvement in their vision.

Retinal Implants

Retinal implants, also known as bionic eyes, are electronic devices designed to restore some degree of vision in individuals with severe vision loss. These devices convert light into electrical signals that stimulate the remaining healthy retinal cells. Although still under investigation, retinal implants offer hope for individuals with advanced choroideremia.

Vitamin A Supplementation

Some studies suggest that high-dose vitamin A supplementation may help slow retinal degeneration in individuals with choroideremia. However, the evidence remains inconclusive, and supplementation should only be taken under the guidance of a healthcare provider.

Emerging Therapies

CRISPR-Cas9 Gene Editing

CRISPR-Cas9 gene-editing technology has the potential to correct the genetic mutation responsible for choroideremia. This approach aims to repair the defective CHM gene and restore its normal function. Although still in the research stage, it represents a promising future treatment option.

Stem Cell Therapy

Stem cell therapy focuses on replacing damaged retinal cells with healthy cells derived from stem cells. While still experimental, early research suggests it may help regenerate retinal tissue and improve vision in the future.

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How to Live with Choroideremia?

Coping Strategies

Living with progressive vision loss can be challenging. Individuals with choroideremia and their families should seek support from ophthalmologists, low vision specialists, rehabilitation services, and support groups. Assistive technologies such as magnifiers, screen readers, and mobility aids can help maintain independence and improve quality of life.

Regular Monitoring

Routine eye examinations are essential for monitoring disease progression. Early detection of changes in vision allows timely intervention and appropriate management to help preserve remaining vision.

Research and Clinical Trials

Individuals with choroideremia may consider participating in clinical trials to contribute to ongoing research and gain access to emerging therapies. Clinical studies play a vital role in developing safer and more effective treatment options for this rare genetic condition.