How is Choroideremia diagnosed?

Choroideremia is a rare genetic disorder that primarily affects the retina, leading to progressive vision loss. Diagnosing this condition involves a combination of clinical evaluation, genetic testing, and specialized eye examinations.

Clinical Evaluation: The first step in diagnosing choroideremia involves a thorough clinical evaluation by an ophthalmologist or a retina specialist. The doctor will review the patient's medical history, including any family history of vision problems or genetic disorders. They will also conduct a comprehensive eye examination, which may include visual acuity tests, visual field tests, and a dilated eye examination to assess the health of the retina and other structures in the eye.

Genetic Testing: Choroideremia is caused by mutations in the CHM gene, which is responsible for producing a protein called REP-1. Genetic testing can identify these mutations and confirm the diagnosis of choroideremia. The most common method of genetic testing is DNA sequencing, which involves analyzing a blood or saliva sample to identify any changes or abnormalities in the CHM gene. Genetic testing can also help determine if a person is a carrier of the condition, which is particularly important for family planning purposes.

Electroretinography (ERG): ERG is a specialized eye test that measures the electrical activity of the retina in response to light stimulation. It can help assess the function of the photoreceptor cells in the retina, which are primarily affected in choroideremia. During the test, the patient's eyes are dilated, and electrodes are placed on the surface of the eye to record the electrical signals. The results of the ERG test can provide valuable information about the severity and progression of the disease.

Ocular Coherence Tomography (OCT): OCT is a non-invasive imaging technique that uses light waves to create detailed cross-sectional images of the retina. It can help visualize the layers of the retina and detect any structural abnormalities. In choroideremia, OCT can reveal thinning of the choroid and the outer retina, which are characteristic features of the condition. This imaging technique is particularly useful for monitoring disease progression over time.

Family History: Choroideremia is an X-linked recessive disorder, which means it primarily affects males and is passed down through generations. Therefore, obtaining a detailed family history is crucial in diagnosing choroideremia. If there is a family history of vision loss or known cases of choroideremia, it increases the suspicion for the condition and may prompt further genetic testing.

In conclusion, diagnosing choroideremia involves a combination of clinical evaluation, genetic testing, and specialized eye examinations. A thorough assessment of the patient's medical history, genetic testing to identify CHM gene mutations, and specialized tests like ERG and OCT are essential for an accurate diagnosis. Early diagnosis is crucial for appropriate management and genetic counseling for affected individuals and their families.