DIS - Inherited Retinal Disease - Week 2 Flashcards
What are most genetic diseases and how is AMD different to them?
Many inherited retinal diseases are monogenic
AMD involves multiple genes, environmental factors, dietary factors, and lifestyle habits
Can the exact same mutations in one gene cause different disease presentations or do they always have the same outcome?
Can cause different presentations
-epistasis
Define epistasis.
A form of gene-gene interaction in which genes not directly involved in causing the disease have an effect on the phenotypic expression of the disease trait (caused by the mutation in another gene)
What are rod-cone dystrophies?
A family of progressive diseases in which rod dysfunction is more severe than cone dysfunction
Can rod-cone dystrophies cause night blindness?
Yes
What kind of vision loss do rod-cone dystrophies cause?
Peripheral loss
Describe the severity and progression of rod-cone dystrophies at birth or if developed in childhood.
Severe at birth, with little progression
Can be developed in childhood with rapid progression
-usually results in severe vision loss and nystagmus
Describe how delayed onset rod-cone dystrophies differ from early onset. Do they result in complete vision loss or nystagmus?
Symptoms develop late and progress more slowly
Rarely results in near complete vision loss or nystagmus
What kind of disease is lebers congenital amaurosis and what kind of mode of inheritance does it have? Is it common or rare?
Common form of early onset rod-cone dystropy
Autosomal recessive
What kind of vision is present since birth for those with lebers congenital amourosis? What else is present?
Very poor vision with roving nystagmus
What is the fundus like in lebers congenital amourosis?
May appear normal or may show abnormalities
Is ERG normal or abnormal with lebers congenital amourosis?
Abnormal
Is x-linked retinitis pigmentosa a common or uncommon form of retinitis pigmentosa? What about rod-cone dystrophy?
Common form of early onset rod-cone dystrophy, but not a common form of RP overall
Which gender is usually fully affected with x-linked retinitis pigmentosa? Explain.
Males usually fully affected
Females often have milder form (can be fully affected)
What is vision like in childhood with x-linked retinitis pigmentosa? What eventually happens?
Fairly good vision in childhood, but lose both peripheral and central vision rapidly
How many genes have been implicated in x-linked retinitis pigmentosa?
At least 6
What is the most common form of retinitis pigmentosa?
Autosomal recessive
List three classical features of retinitis pigmentosa.
Night blindness
Loss of peripheral vision
Intraretinal pigmentation
-bone spicule-like
Are the dominant or recessive forms of retinitis pigmentosa often more severe?
Recessive forms often more severe
How many genes are implicated in autosomal recessive retinitis pigmentosa?
At least 25
What is the second-most common form of retinitis pigmentosa?
Autosomal dominant
Does autosomal dominant retinitis pigmentosa have the classical features of retinitis pigmentosa?
Yes
Describe the severity, age of onset, and penetrance of autosomal dominant retinitis pigmentosa (2).
It varies widely depending on abnormal function gained and haploinsufficiency
Is it easy or difficult to predict causal gene from the observed phenotype in autosomal dominant retinitis pigmentosa?
Difficult
How many genes are implicated in autosomal dominant retinitis pigmentosa?
At least 18
Describe cone-rod dystrophies.
Family of progressive diseases in which cone dysfunction is more severe than rod dysfunction
What kind of vision loss is expected in cone-rod dystrophies?
Loss of central vision - central scotoma
What is seen on ERG with cone-rod dystrophies?
Cone-driven ERG responses affected
Is retinal damage typically seen with cone-rod dystrophies?
Yes
-atrophy and/or pigmentary changes
True or false
Cone dystrophies are allelic to cone-rod dystrophies
Explain what this means.
True
Cone and cone-rod dystrophies
represent phenotypic variations of the same disease
True or false
Cone and cone-rod dystrophies do not cause light aversion.
False
They do
How many genes are implicated for the following cone and cone-rod dystrophies?
X-linked
Autosomal recessive
Autosomal dominant
X-linked - at least 1
Autosomal recessive - at least 13
Autosomal dominant - at least 13