Inherited Dystrophies Flashcards
What is a dystrophy?
They are usually bilateral and have symmetry. They run in families. Usually develops after inheriting a faulty gene from one or both parents. Faulty gene caused by mutations (alterations). Certain functions can no longer be performed or adequately performed due to faulty gene.
What is Retinitis Pigmentosa?
s a rod – cone dystrophies which is progressive. It’s a group of disease. Primary degeneration of rod photoreceptors followed by cone photoreceptors. Inner retina becomes progressively disorganised as the outer retina degenerates (where the rod photoreceptors are). It has a worldwide prevalence of 1:4000. Initial symptom of reduced night vision followed by progressive VF loss due to rod photoreceptors being affected first. Macular function usually well preserved until the later stages. 20 – 30% have a syndromic (has other conditions in other parts of the body e.g. RP patients can have hearing disorders) form of RP. Chief gene mutation relate to defects in activation/deactivation of the visual pigment or pathways involved in the visual phototransduction cascade. Various phenotypes (i.e., observable traits) result from multiple mutations
What are the fundus abnormalities expected from RP?
Fundus abnormalities:
- Bone spicule pigmentation predominantly in the periphery and/or mid – periphery (pigmentation is sometimes absent in early stages)
- Attenuation of retinal blood vessels
- Waxy pallor of ONH
What are the various patterns of inheritance for RP?
Various patterns of inheritance:
- X – linked (5 – 16%) ►most severe symptoms, less common
- Autosomal recessive (50 – 60%)
- Autosomal dominant (30 – 40%) ►best long-term prognosis
What is Congenital Stationary night blindness (CSNB)?
is a disorder affecting the rod system and it’s a stationary disorder – it had very little progression. It a group of diseases that result in poor night vision. At least 17 genes found to be associated with CSNB which includes genes encoding proteins involved in:
- Phototransduction
- Photoreceptor to bipolar cell signalling cascades
- Retinoid recycling
What are the classification for CSNB
- Riggs is less common and Schubert Bornschein type is more common
- Diagnosis with a dependent on ERG results
- Fundus ablipunctatus – is where numerus white dots in the periphery may change as the age, when the patient is young they appear as flecks and become spots over time. They can increase and decrease in number over the years.
- Oguchi Disease – it’s a gold colour reflective of the fundus, after hours of dark adaptation is fundus can appear in a normal colour but will return back once exposed to light. This is called the Mizuo Nakamura phenomenon
What is Cone - Rod dystrophy syndrome?
usually not symptomatic until late childhood/early adulthood. Visual acuity deteriorates over time to the level of 6/60 to counting fingers. Signs and symptoms include colour vision defects, “bull’s eye” appearance on fundus in early stage, macular atrophy develops over time. In late stages signs and symptoms may include peripheral RPE atrophy, retinal pigmentation, arteriolar attenuation, and optic disc pallor. Various patterns of inheritance:
- Autosomal dominant
- Autosomal recessive ►most common
- XL recessive ►least common
What is Leber Congenital Amaurosis (LCA)
its congenital or presents within the first few months of life. Visual acuity often remains stable although progression is seen sometimes. Signs and symptoms include nystagmus, no light perception to 6/30, often hypermetropic and poor pupil responses ►reflects severe retinal dysfunction. Undetectable full – field electroretinogram (ERG) in most cases. Some genes associated with more of the rod – cone disease while others with cone – rod disease. Fundoscopic retinal phenotype is very variable. Majority present with normal fundus or few abnormalities at birth. With time, the following change may occur:
What are the expected finding on a fundus of a patient with Leber Congentital amaurosis (LCA)
- Chorioretinal atrophy with narrowing of retinal vasculature
- Spicular/nummular intraretinal pigment migration
- Intra – subretinal white flecks
- Optic disc pallor
- Macular atrophy
These symptoms can be found in which disease?
- Chorioretinal atrophy with narrowing of retinal vasculature
- Spicular/nummular intraretinal pigment migration
- Intra – subretinal white flecks
- Optic disc pallor
- Macular atrophy
Leber congenital Amaurosis
What is stargardt disease?
Stargardt disease – autosomal recessive macular dystrophy, a.k.a. Fundus flavimaculatus. Typically occurs in childhood between the ages of 7 and 15 years but there can also be adult onset forms. Causes loss of central vision, with vison deteriorating more rapidly in childhood onset form and most cases have a VA of 6/60 or worse within 2 – 3 years of disease onset. Central scotoma with preserved peripheral field in early stages, but peripheral field loss in some cases. There can be diffuse dystrophy in late stage in some cases. The fundus can be normal in early stages. Typically central macular atrophy at presentation and most cases develop white yellow flecks at level of RPE.
What is Best Vitelliform Macular Dystrophy?
belongs to a group of diseases called bestrophinopathies. Mutations in the BEST1 gene which encodes the multifunctional protein bestrophlin – 1 that is present in the RPE. Variable age of onset ranging from first decade to beyond 6th decade (mean age at onset within 4th decade). Mildly to markedly hyperopic. Reduced VA and metamorphopsia. Adult-onset form → Adult-onset foveomacular vitelliform dystrophy (mild loss of VA, usually after the age of 35)
List the stages of Best Vitelliform Macular Dystrophy
Stages of Best Vitelliform Macular Dystrophy
1. Pre Vitelliform stage
2. Vitelliform stage
3. Vitelliruptive
4. Pseudohypopyon
5. Atrophic
6. Cicatricial Stage
o Note: The vitelliruptive stage and pseudohypopyon stage may evolve back and fourth for several years.
What is Pattern Dystrophy?
A group of diseases characterised by variable distributions of pigment deposition at the level of the RPE. Often present in 4th to 5th decades. Mildly reduced VA. Usually good prognosis unless complicated by choroidal neovascularisation (CNV)
What is sorsby fundus dystrophy?
Central visual loss in 5th decade of life. Early signs are macular yellowish grey drusen-like deposits at the level of Bruch’s membrane which preferentially accumulate along the temporal arcades. Deposits progress over time to include the central macula. CNV is a common complication which can result in severe VA loss.
