cone-rod dystrophy 21

Cone-Rod Dystrophy 21: A Rare Inherited Retinal Disorder

Cone-rod dystrophy 21, also known as CORD21, is a rare inherited retinal disorder that affects the retina's ability to detect light and color. This condition is characterized by the degeneration of both cone and rod photoreceptors in the retina.

Key Features:

• Retinal Pigment Deposits: Cone-rod dystrophy 21 is marked by the presence of retinal pigment deposits, particularly in the macular region.
• Vision Loss: The disorder leads to progressive vision loss, which becomes more severe over time.
• Inherited Trait: CORD21 is inherited in an autosomal recessive manner, meaning that a person must inherit two copies of the mutated gene (one from each parent) to develop the condition.

Symptoms:

• Night Blindness: Individuals with cone-rod dystrophy 21 often experience night blindness due to the degeneration of rod photoreceptors.
• Reduced Visual Acuity: The disorder leads to reduced visual acuity, making it difficult for affected individuals to read, recognize colors, or perform daily activities that require good vision.
• Color Vision Defects: Cone-rod dystrophy 21 is characterized by color vision defects, as the cone photoreceptors responsible for detecting colors are also affected.

Prevalence and Genetics:

• Rare Condition: Cone-rod dystrophy 21 is a rare condition, with an estimated prevalence of 1 in 40,000 people.
• Genetic Heterogeneity: The disorder can be caused by mutations in the DRAM2 gene on chromosome 1p13.

References:

• [3] A number sign (#) is used with ... retinal dystrophy with early macular involvement (CORD21) is caused by homozygous or compound heterozygous mutation in the DRAM2 gene (613360) on chromosome 1p13.
• [4] Clinical features · Macular atrophy · Night blindness · Reduced visual acuity · Retinal dystrophy.
• [14] Any cone-rod dystrophy in which the cause of the disease is a mutation in the DRAM2 gene. Synonyms. CORD21; DRAM2 cone-rod dystrophy; cone-rod dystrophy 21 ...

Early Signs and Symptoms

The first signs and symptoms of cone-rod dystrophy often occur in childhood and include decreased sharpness of vision (visual acuity) [1, 4]. This is followed by increased sensitivity to light (photophobia) [9] and abnormalities in retinal imaging, such as a bull's eye maculopathy and RPE atrophy.

Progressive Vision Loss

As the disease progresses, symptoms worsen and may include:

• Blind spots in the central field of vision (scotomas)
• Loss of color perception
• Loss of peripheral vision [7]
• Night blindness and loss of peripheral vision, which reflect the predominant involvement of cones, leading to decreased visual acuity [5]

Key Symptoms

The key symptoms of cone-rod dystrophy include:

• Decreased visual acuity
• Color vision defects
• Decreased sensitivity in the central visual field [6]
• Blind spots in the central field of vision (scotomas)
• Loss of color perception and loss of peripheral vision

These symptoms are usually followed by a progressive loss of rod photoreceptor cells, leading to further deterioration of vision.

Diagnostic Tests for Cone-Rod Dystrophy 21

Cone-rod dystrophy 21, a rare genetic disorder affecting the eyes, can be diagnosed through various clinical and genetic tests.

• Clinical Features: The condition is characterized by progressive vision loss, which becomes more severe over time [3]. A thorough eye examination, including an electroretinogram (ERG), can help identify the condition.
• Genetic Testing: Genetic testing can confirm the diagnosis of cone-rod dystrophy 21. This involves analyzing genes associated with the condition, such as ABCA4, RPGRIP1, ADAM9, and CERKL [5].
• Specific Diagnostic Codes: The International Classification of Diseases (ICD-9) codes for cone-rod dystrophies are listed under code 21.0 to 21.9 [10].

Available Genetic Tests

Several genetic testing options are available for cone-rod dystrophy 21, including:

• Blueprint Genetics' Cone Rod Dystrophy Panel: This panel is ideal for patients with a clinical suspicion or diagnosis of cone rod dystrophy [2].
• Molecular Vision Laboratory's Clinical Genetic Test: This test offers comprehensive analysis of genes associated with various conditions, including cone-rod dystrophy 3 and achromatopsia [4].

Important Considerations

When interpreting genetic testing results, it is essential to consider the clinical findings in context. In some cases, genetic testing may be inconclusive or detect a variant of unknown significance [6]. Therefore, a comprehensive evaluation by an eye care professional is necessary for accurate diagnosis and management.

References:

[2] Blueprint Genetics' Cone Rod Dystrophy Panel Is ideal for patients with a clinical suspicion / diagnosis of cone rod dystrophy. [3] Mar 1, 2018 — Cone-rod dystrophy is a group of related eye disorders that causes vision loss, which becomes more severe over time. [4] Clinical Genetic Test offered by Molecular Vision Laboratory for conditions (51): Cone-rod dystrophy 3; Achromatopsia 2; Achromatopsia 3; ... Testing genes ... [5] A study based on literature searches (RetNet) reports that the autosomal recessive Cone-Rod Dystrophy (AR CRD) genes ABCA4, RPGRIP1, ADAM9 and CERKL are ... [6] Feb 11, 2022 — Genetic testing was inconclusive, detecting a previously unpublished variant of unknown significance in a gene that may cause cone-rod dystrophy ...

Current Status of Drug Treatment for Cone-Rod Dystrophy

As of now, there are no proven treatments for Cone-Rod Dystrophies (CRD) [1]. However, researchers have been exploring potential solutions, including gene therapy. A study in 2022 found that mice with CDHR1 mutations were treated with a gene therapy called SPVN06 investigational gene therapy, which showed promise in restoring some sight to the mice [6].

Unfortunately, this treatment is still in its experimental stages and has not been approved for human use yet. In fact, as of now, there are no treatments available for most patients with CRD [6]. The current management approach focuses on alleviating symptoms and optimizing visual function through consultation with a vision specialist [5].

Research and Future Directions

While there is still much to be learned about CRD, researchers are actively investigating potential solutions. Gene therapy has shown promise in restoring some sight to mice with cone dystrophy, but more research is needed before it can be considered for human use [9]. It's essential for individuals with CRD to stay informed about the latest developments and consult with a vision specialist for personalized guidance.

Key Points:

• No proven treatments exist for Cone-Rod Dystrophies as of now.
• Gene therapy has shown promise in restoring some sight to mice with cone dystrophy, but more research is needed.
• Current management focuses on alleviating symptoms and optimizing visual function through consultation with a vision specialist.
• Research continues to explore potential solutions for CRD.

References:

[1] Feb 4, 2019 — There are no proven treatments for Cone-Rod Dystrophies as of yet, although recent years have noted advances in clinical research and ... [5] While studies are underway investigating potential solutions, no cure has been identified. It is suggested that people with CRD consult a vision specialist to ... [6] May 9, 2024 — No treatment is currently available to most patients,” Gow and colleagues wrote in their poster. “SPVN06 investigational gene therapy is ... [9] Research. Gene therapy has restored some sight to mice with cone dystrophy. More research is needed before we can say whether it could be used in humans too.

Differential Diagnosis of Cone-Rod Dystrophy

Cone-rod dystrophy (CRD) is a progressive degenerative disorder predominantly affecting retinal cones, with varying patterns of inheritance. When diagnosing CRD, it's essential to consider other hereditary and acquired disorders that may present similar symptoms.

Other Hereditary Disorders:

• Achromatopsia: A rare genetic disorder characterized by cone dysfunction, leading to severe visual impairment.
• Cone dystrophy: A rare genetic retinal disorder primarily affecting cones, with variable fundus appearance.
• Stargardt disease: An autosomal-recessive inherited macular degeneration that may be confused with CRD due to similar symptoms.

Acquired Disorders:

• Retinitis pigmentosa (RP): A group of genetic disorders causing progressive vision loss, which can be distinguished from CRD by the sequence of photoreceptor involvement (rod photoreceptors followed by cone photoreceptors).
• Choroideremia: An X-linked recessive rod-cone dystrophy characterized by marked atrophy of the choroid and retinal pigment epithelium.

Key Considerations:

When diagnosing CRD, it's crucial to consider these differential diagnoses and rule out other conditions that may present similar symptoms. A comprehensive evaluation, including clinical history, fundus examination, and electrophysiological tests (such as electroretinography), can help establish a definitive diagnosis.

Citations:

• [1] Cone-rod dystrophy. ... Differential Diagnosis. Each retinal dystrophy phenotype is often confused with other genetic or acquired disorders. Misdiagnosis is common and must be avoided, as it has a great bearing on genetic and prognostic counseling.
• [5] Differential diagnosis includes other hereditary cone disorders (including achromatopsia and allied cone dysfunction syndromes, cone dystrophy, and Stargardt disease).
• [10] Cone rod dystrophies (CRDs) are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region.
• [11] Differential diagnosis of non-syndromic CRDs with other pigmentary retinopathies, including retinitis pigmentosa and choroideremia.