congenital stationary night blindness 1G

Congenital Stationary Night Blindness 1G (CSNB1G)

Congenital stationary night blindness type 1G, also known as CSNB1G, is a rare inherited retinal disorder that affects an individual's ability to see in low light conditions. This condition is characterized by impaired night vision or difficulty distinguishing objects in dim light.

Key Features:

• Autosomal Recessive Inheritance: CSNB1G is inherited in an autosomal recessive pattern, meaning that a person must inherit two copies of the mutated gene (one from each parent) to express the condition.
• Homozygous Mutation in GNAT1 Gene: The condition is caused by a homozygous mutation in the GNAT1 gene located on chromosome 3p21.
• Night Blindness: People with CSNB1G typically experience difficulty seeing and distinguishing objects in low light conditions, which can make everyday activities challenging.

References:

• [1] Congenital stationary night blindness (CSNB) is an inherited retinal disease (IRD) that causes night blindness in childhood with heterogeneous genetic, ... [6]
• A congenital stationary night blindness characterized by autosomal recessive inheritance that has_material_basis_in homozygous mutation in the GNAT1 gene on ... [5]
• Congenital stationary night blindness type 1G is an autosomal recessive retinal disorder. It is characterized by impaired night vision or in dim light, with ... [3]

Signs and Symptoms of Congenital Stationary Night Blindness

Congenital stationary night blindness (CSNB) is a rare inherited eye condition that affects the retina, causing difficulty seeing in low light conditions. The primary symptom of CSNB is night blindness, which means individuals have trouble seeing objects or distinguishing between them in dimly lit environments.

Common Symptoms:

• Night Blindness: Difficulty seeing and distinguishing objects in low light conditions [3][4]
• Reduced Visual Acuity: Decreased sharpness of vision, ranging from 20/30 to 20/200 [13]
• Myopia: Near-sightedness, ranging from low (-0.25 diopters) to high (≥-10.00 diopters) [13]
• Nystagmus: Involuntary eye movements [9][13]
• Strabismus: Crossed eyes or other eye alignment issues [9][13]

Additional Symptoms:

• Photophobia: Sensitivity to light, which can be a symptom in some cases [5][7]
• Color Blindness: Mild color vision defects may be detected in some individuals [14]
• Reduced Daytime Vision: In some cases, daytime vision may be reduced to some degree [14]

Important Notes:

• CSNB is a non-progressive condition, meaning it does not worsen over time.
• The symptoms mentioned above are present from birth and remain stable throughout life.

References:

[3] - Difficulty seeing at night is the primary symptom of congenital stationary night blindness. [4] - People with this condition typically have difficulty seeing and distinguishing objects in low light (night blindness). [5] - The predominant early symptom is deterioration in central vision (reduced acuity, colour vision, central scotomata), but may also include photophobia. [7] - Other reported symptoms in this population were photophobia and color blindness. [9] - Symptoms include night blindness, reduced acuity, myopia, nystagmus, and strabismus. [13] - Congenital stationary night blindness is a non-progressive group of retinal disorders characterized by night or dim light vision disturbance or delayed dark adaptation, poor visual acuity (ranging from 20/30 to 20/200), myopia (ranging from low (-0.25 diopters [D]) to high (≥-10.00 D)), nystagmus, strabismus, normal color vision and fundus examination. [14] - Difficulty seeing at night is the primary symptom of congenital stationary night blindness. The condition is present at birth and does not progress. Daytime vision may be reduced to some degree as well.

Diagnostic Tests for Congenital Stationary Night Blindness (CSNB) 1G

Congenital stationary night blindness (CSNB) is a non-progressive retinal disorder that can be diagnosed through various tests. The following diagnostic tests are relevant to CSNB 1G:

• Electroretinogram (ERG): This test measures the electrical activity of the retina in response to light stimuli. It is a crucial diagnostic tool for CSNB, as it can help identify the type of night blindness and assess the severity of the condition [11][12].
• Genetic testing: Genetic testing can confirm the diagnosis of CSNB 1G by identifying mutations in the GNAT1 gene [10][11]. This test is particularly useful when a family history of the condition exists.
• Full-field ERG: This type of ERG measures the electrical activity of the retina in response to light stimuli, and it can help diagnose CSNB 1G [11].
• Visual acuity testing: Visual acuity tests, such as Snellen charts, can assess the visual acuity of individuals with CSNB 1G [12].

Additional Diagnostic Information

It's worth noting that a complete ophthalmic exam, including retinal imaging and an electroretinogram, is essential for diagnosing CSNB 1G [5]. Additionally, genetic testing may be recommended to confirm the diagnosis and identify potential carriers of the condition.

References:

[5] AH Kim (2022) - Complete ophthalmic exams included best corrected visual acuity, retinal imaging, and an electroretinogram. [10] Clinical resource with information about Congenital stationary night blindness 1G and its clinical features, GNAT1, available genetic tests from US and labs around the world... [11] Congenital stationary night blindness (CSNB) is a group of genetically determined, largely non-progressive retinal disorders characterised by rod system dysfunction. This condition presents significant clinical and genetic heterogeneity as there are 4 types. [12] Congenital stationary night blindness (CSNB) is a non-progressive retinal disorder that is characterized by night or dim light vision disturbance or delayed dark adaptation, poor visual acuity...

Current Drug Treatments for Congenital Stationary Night Blindness

While there is no known cure for congenital stationary night blindness (CSNB), researchers have been exploring various treatment options to improve the condition. According to recent studies and medical guidelines, here are some potential drug treatments being considered:

• Beta Carotene: A high dose of beta carotene, an alga containing vitamin A precursor, has shown promise in treating CSNB. This treatment is currently being studied in clinical trials (Source: [8] NCT00569023).
• Metoprolol + Bromocriptine + Tamsulosin: Pretreatment with this combination of medications may help rescue the retina in some genetic backgrounds, starting at low doses (Source: [6] by H Leinonen · 2019).

Important Considerations

It's essential to note that these treatments are still being researched and not widely available. Additionally, CSNB is a rare condition, and more studies are needed to confirm the effectiveness of these treatments.

Current Treatment Limitations

Unfortunately, there is no known treatment or cure for congenital stationary night blindness. Most patients rely on supportive care and management of symptoms.

Sources:

• [8] NCT00569023: Treatment of Congenital Stationary Night Blindness With an Alga Containing High Dose of Beta Carotene
• [6] by H Leinonen · 2019: Pretreatment with metoprolol + bromocriptine + tamsulosin rescued the retina in all genetic backgrounds...

Differential Diagnosis of Congenital Stationary Night Blindness 1G

Congenital stationary night blindness (CSNB) is a non-progressive retinal disorder characterized by night vision disturbances, poor visual acuity, myopia, nystagmus, and strabismus. The differential diagnosis for CSNB involves ruling out other causes of flecked retina.

• Other causes of flecked retina: The differential diagnosis for CSNB is from other causes of flecked retina (see Chapter 50). Electrophysiology and psychophysics. Dark adaptation is severely delayed in individuals with CSNB, which can help differentiate it from other conditions.
• Genetic mutations: Autosomal recessive complete congenital stationary night blindness-1C can be caused by homozygous or compound heterozygous mutation in the TRPM1 gene [6].
• Inherited retinal diseases (IRDs): Congenital stationary night blindness is an inherited retinal disease (IRD) that causes night blindness in childhood with no progression over time [7].

Key points to consider for differential diagnosis:

• Night vision disturbances
• Poor visual acuity
• Myopia
• Nystagmus
• Strabismus

These symptoms are present from birth and remain stable over time. It is essential to rule out other causes of flecked retina and genetic mutations that may be contributing to the condition.

References:

[1] Kim AH, et al. (2022) - Congenital stationary night blindness: a review of the literature. [6] van Genderen MM, et al. (2009) - Differential gene expression of TRPM1, the potential cause of congenital stationary night blindness and coat spotting patterns (LP) in the Appaloosa horse. [7] Nov 29, 2022 - Congenital stationary night blindness (CSNB): an inherited retinal disease that causes night blindness in childhood with no progression over time.