ERG changes

Flecked Retina Syndromes

Clinical Characteristics
Ocular Features: 

There exist a considerable number of disorders often classified under the heading of 'flecked retina' syndrome.  Prior to the modern genomic period, distinctions among them were based on the clinical picture, functional abnormalities, and electrophysiological studies.  The nosology is becoming clearer as more individuals are genotyped and we can expect further discrimination of these disorders in the near future.

White or yellow discrete dots are found throughout the fundus.  These are most dense in the midperiphery RPE and the macula is generally not involved.  This is most common in patients with fundus albipunctatus who have a nonprogressive disease.  Stationary night blindness is the predominant symptom.  However, patients with mutations in RDH5 may have more serious cone involvement and progressive macular disease.  Visual acuity varies from near normal to severe loss.  Photopic ERGs may be normal but only low scotopic responses can be recorded in such patients.  Cone dysfunction is more severe in older patients.

Systemic Features: 

No systemic disease is associated with these syndromes.

Genetics

These disorders are sometimes grouped into the category of 'flecked retina disease'.

Autosomal dominant inheritance is typical for fundus albipunctatus (136880) resulting from mutations in the RDS (PRPH2) gene (6p21.1-cen).

Autosomal recessive fundus albipunctatus (136880) is caused by mutations in RDH5 (12q13-q14) and sometimes in RLBP1 (15q26.1).

Retinitis punctata albescens (136880) and fundus albipunctatus (136880) may both be caused by mutations in RLBP1 (15q26.1).  In a consanguineous family in which younger individuals (aged 3-20 years) had signs of fundus albipunctatis, older individuals in the fourth and fifth decades of life had features of retinitis punctata albescens (136880).  Homozygous mutations in RLBP1 were found in all individuals.  Homozygous mutations in the same gene are also responsible for Bothnia type retinal dystrophy (607475) and for the Newfoundland type of retinal dystrophy (607476).

Familial Benign Fleck Retina (228980) is characterized by a normal ERG and normal vision. The macula is spared from the white/yellow flecks located behind retinal vessels. Autofluorescence is present and the fluorescein angiogram shows irregular hypofluorescence.  Nothing is known about the mutation but the clinical condition is inherited in an autosomal recessive pattern.

Some group Stargardt disease (248200), fleck retina of Kandori (228990),  juvenile retinoschisis (312700), and familial benign fleck retina (228980) as well into the category of 'flecked retina disease'.

Other disorders in which retinal flecks may be seen are: spastic paraplegia 15 (270700), hyperoxaluria (259900), Alport syndrome (301050), Bietti-crystalline-corneoretinal-dystrophy (210370 ), Sjogren-Larsson syndrome (270200), pantothenate kinase-associated neurodegeneration (234200), Leber congenital amaurosis (204000), and Bardet-Biedl syndrome (209900),

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

Low vision aids may be useful when macular disease is present.  A recent report describes improvement in peripheral fields and rod function following administration of high-dose oral 9-cis-beta-carotene.

References
Article Title: 

Flecked-retina syndromes

Walia S, Fishman GA, Kapur R. Flecked-retina syndromes. Ophthalmic Genet. 2009 Jun;30(2):69-75..

PubMed ID: 
19373677

Novel mutations in the cellular retinaldehyde-binding protein gene (RLBP1) associated with retinitis punctata albescens: evidence of interfamilial genetic heterogeneity and fundus changes in heterozygotes

Fishman GA, Roberts MF, Derlacki DJ, Grimsby JL, Yamamoto H, Sharon D, Nishiguchi KM, Dryja TP. Novel mutations in the cellular retinaldehyde-binding protein gene (RLBP1) associated with retinitis punctata albescens: evidence of interfamilial genetic heterogeneity and fundus changes in heterozygotes. Arch Ophthalmol. 2004 Jan;122(1):70-5.

PubMed ID: 
14718298

Benign fleck retina

Isaacs TW, McAllister IL, Wade MS. Benign fleck retina. Br J Ophthalmol. 1996 Mar;80(3):267-8. PubMed PMID: 8703867

PubMed ID: 
8703867

Abetalipoproteinemia

Clinical Characteristics
Ocular Features: 

The major ocular manifestations of abetalipoproteinemia are in the retina which develops diffuse and sometimes patchy pigmentary changes often called atypical retinitis pigmentosa.  In other cases the picture resembles retinitis punctata albescens with perivascular white spots in the peripheral retina.  Night blindness is an early and prominent symptom with abnormal dark adaptation thresholds evident before fundus pigment changes are seen.  The ERG shows loss of rod function before that of cone function.  The macula may or may not be affected while peripheral fields are often severely constricted.  Loss of photoreceptors occurs throughout life and visual fields show progressive constriction, sometimes with central sparing.  A single case of bilateral disc swelling in a 9 year-old girl has been reported.

Systemic Features: 

Celiac disease and steatorrhea due to a deficiency of circulating chylomicra underlie the malabsorption of vitamins A and E which is probably responsible for the majority of systemic manifestations.  Red blood cells have a peculiar burr-like morphology that has led to the designation 'acanthocytes'.  Liver failure and cirrhosis sometimes occur.  Plasma lipids are generally low including cholesterol, triglycerides, and beta lipoproteins.  Central and peripheral nerve demyelination occurs leading to a progressive ataxia and other neurological symptoms.

Genetics

This autosomal recessive disease seems to result from an inability to synthesize the apoB peptide that is a part of the LDL and VLDL.   A mutation in the MTP gene (4q22-q24) is responsible.  The gene is sometimes called MTTP as it codes for micosomal triglyceride transfer protein.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Treatment with vitamins A and E may be beneficial.  Cone function improves before rod function with massive doses of vitamin A but usually only after months of treatment.  It has been reported that Vitamin A alone without vitamin E is insufficient to arrest the retinal disease.

References
Article Title: 
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