Oguchi disease

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Oguchi disease
Synonyms	Congenital stationary night blindness type 2
Pronounce	N/A
Specialty	N/A
Symptoms	Night blindness, abnormal fundus reflex
Complications	N/A
Onset	Childhood
Duration	Lifelong
Types	N/A
Causes	Mutations in the SAG or GRK1 genes
Risks	Consanguinity
Diagnosis	Electroretinography, genetic testing
Differential diagnosis	Retinitis pigmentosa, fundus albipunctatus
Prevention	N/A
Treatment	No specific treatment; low vision aids
Medication	N/A
Prognosis	Stable vision with no progression
Frequency	Rare
Deaths	None directly attributable

Oguchi disease is a rare, autosomal recessive congenital stationary night blindness (CSNB) disorder characterized by a unique golden or grayish discoloration of the retina that reverses after prolonged dark adaptation. This condition is named after the Japanese ophthalmologist Chuta Oguchi, who first described it in 1907.

Clinical Features

Patients with Oguchi disease typically present with night blindness (nyctalopia) from an early age. Despite the significant difficulty in seeing in low-light conditions, their daytime vision remains relatively normal. The hallmark of Oguchi disease is the Mizuo-Nakamura phenomenon, where the abnormal golden or grayish discoloration of the retina disappears after several hours of darkness, revealing a normal-appearing retina.

Pathophysiology

Oguchi disease is caused by mutations in genes involved in the phototransduction pathway in the retina. The two primary genes associated with this condition are SAG (S-arrestin) and GRK1 (G protein-coupled receptor kinase 1). Mutations in these genes disrupt the normal function of rod photoreceptors, leading to impaired dark adaptation and night blindness.

Diagnosis

The diagnosis of Oguchi disease is primarily clinical, based on the characteristic retinal appearance and the Mizuo-Nakamura phenomenon. Electroretinography (ERG) can be used to confirm the diagnosis, showing a typical pattern of reduced rod function with relatively preserved cone function. Genetic testing can identify mutations in the SAG or GRK1 genes, providing a definitive diagnosis.

Treatment

There is currently no cure for Oguchi disease. Management focuses on coping strategies for night blindness, such as using bright lighting and avoiding activities in low-light conditions. Genetic counseling may be beneficial for affected individuals and their families.

Epidemiology

Oguchi disease is extremely rare, with most cases reported in Japan. However, it has been identified in various populations worldwide. The exact prevalence is unknown due to its rarity and the potential for misdiagnosis as other forms of night blindness.

See Also

• Night blindness
• Congenital stationary night blindness
• Retina
• Phototransduction
• Electroretinography

External Links

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