night blindness

Retinal Dystrophy, Newfoundland Type

Clinical Characteristics
Ocular Features: 

There is considerable clinical heterogeneity, mostly age-dependent.  Night blindness can occur in early childhood but usually later even though scotopic responses can be undetectable in the first decade of life while photopic responses are reduced on the ERG at all ages.  Both rod and cone responses may be extinguished in later life.  Visual acuity can be decreased beginning in early childhood and legal blindness usually occurs by the second or third decade of life.  However, the loss of vision continues to progress and severe vision loss to finger-counting may be present in older individuals.  A scallop-bordered lacunar atrophy may be seen in the midperiphery.  The macula is only mildly involved by clinical examination although central retinal thinning is seen in all cases.  Dyschromatopsia is mild early and usually becomes more severe.  The visual fields are moderately to severely constricted although in younger individuals a typical ring scotoma is present.  The peripheral retina contains ‘white dots’ and often resembles the retinal changes seen in retinitis punctate albescens.

Systemic Features: 

None reported.

Genetics

Homozygous mutations in the RLBP1 gene (15q26.1) are responsible for this disorder.  Homozygous mutations in RLBP1 have also been found among patients with fundus albipunctatus (136880), retinitis punctata albescens, and in Bothnia type retinal dystrophy (607475),

NFRCD clinically resembles Bothnia type retinal dystrophy (607475) which likewise results from mutations in the RLBP1 gene but the maculae appear normal or have only a mild ‘beaten-bronze’ atrophy.

See Flecked Retina entry for somewhat similar conditions.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Retinitis Pigmentosa 38

Clinical Characteristics
Ocular Features: 

This is a rare clinically heterogeneous condition in which both rods and cones functions are variably affected.  It is a progressive disorder with children often being aware of night vision difficulties during the latter half of the first decade of life.  Reduced vision is often present at this time as well and progressively deteriorates.  Visual fields are constricted to 20-30 degrees.  Rod responses may be nondetectable in the first decade.

Central vision is subnormal as early as childhood and progressively worsens with age.  Dyschromatopsia to some degree is often present early as well and some patients have a maculopathy with a bull’s eye pattern and thinning of the photoreceptor layer seen on OCT.  Attenuated retinal vessels, pale optic discs, and variable fundus pigmentary changes (including pigmentary mottling and bone spicules) have been seen.  The degree and course of the photoreceptor damage is variable leading some to propose that RP38 is primarily a cone-rod dystrophy.

Systemic Features: 

None

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the MERTK gene (2q13).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported but young people especially could benefit from low vision aids and special education therapy.

References
Article Title: 

Retinal Cone Dystrophy 3B

Clinical Characteristics
Ocular Features: 

This is a degenerative disorder in which patients have a progressive deterioration of visual acuity and color vision.  Most patients have significant myopia.  Visual difficulties begin in early childhood with acuity of 20/100 or worse by the second decade of life.  Color vision deficits can be detected in the second decade but nyctalopia occurs later in young adults.  Photophobia is a prominent symptom.  The ERG shows reduced and delayed cone responses.  Rod responses to low intensity flashes are undetectable but increased stimulus intensity leads to an abrupt increase in amplitude, often exceeding the upper limits of normal.

The fundus appears normal in some patients but foveal or parafoveal atrophy, a macular bull’s eye, hyperfluorescence anomalies, and a generalized fine pigmentary retinopathy have been reported.  There may be some temporal pallor in the optic nerves.  Nystagmus and strabismus may be present.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in the KCNV2 gene (9p24.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available for this dystrophy.  Low vision aids and tinted lenses may be helpful.

References
Article Title: 

Retinitis Pigmentosa 25

Clinical Characteristics
Ocular Features: 

There is considerable clinical heterogeneity with a wide range in age of onset and progression.  Night blindness, sometimes with photophobia, has its onset in the second or third decade of life and central acuity can be impacted by age 30 years.  Other patients have no symptoms until the fifth decade.  Some patients lose the ability to perceive light by the sixth decade.  The visual fields are usually constricted although one patient had a central scotoma.  The ERG is usually nonrecordable but other patients may have a variable rod-cone pattern of attenuation.  The retinal vessels are also attenuated and some patients have mild optic atrophy.  The pigmentary retinopathy is also variable with sometimes central lesions and in other patients more peripheral.  One patient had posterior subcapsular cataracts.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal recessive form of retinitis pigmentosa resulting from homozygosity or compound heterozygosity in the EYS gene (6q12).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment has been reported.

References
Article Title: 

Knobloch Syndrome 3

Clinical Characteristics
Ocular Features: 

High myopia and marked nystagmus are cardinal ocular findings.  Night blindness leads to symptoms between 2 and 4 years of age.  Vision loss leads to complete blindness by age 15 to 18.  Visual acuity in young adults is often 20/400 to NLP.  Cataracts with subluxated lenses, glaucoma, and chorioretinal atrophy are often present.  Scattered pigment clumping, attenuation of the retinal vasculature, and prominent choroidal vessels can often be seen.  Marked optic atrophy is usually present.  Phthisis and band keratopathy may be seen in older individuals although no retinal detachments have been reported.  The vitreous is described as degenerated in several patients and a vitreal hemorrhage was seen in one patient.

Systemic Features: 

This variant was identified in a four-generation consanguineous Pakistani family in which detailed information was obtained in 5 members. A hairless, purplish-red patch is usually present in the occipital-parietal region during infancy but becomes smaller as children grow.  No encephalocele is present.  Hearing loss and heart defects have not been reported.  Intelligence is normal.

Genetics

This is an autosomal recessive condition resulting from a presumed homozygous mutation on chromosome 17 (17q11.2).

Other variants of Knobloch syndrome are Knobloch 1 (267750) caused by homozygous mutations in COL18A1 (21q22.3) and Knobloch 2 (608454) secondary to homozygous mutations in ADAMTS18 at 16q23.1.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cataracts and dislocated lenses may be removed.

References
Article Title: 

Congenital Disorder of Glycosylation, Type Ia

Clinical Characteristics
Ocular Features: 

Strabismus, roving eye movements (and nystagmus), and visual inattention are found in nearly all patients. Esotropia with defective abduction seems to be the most common oculomotor finding and may be present at birth.  Cataracts, ocular colobomas, oculomotor apraxia, disc pallor, and glaucoma have also been reported.  Vision is always subnormal. Reports of ocular disease before modern genotyping are not specific to the subtypes of CDG I now recognized.

This is a congenital, progressive disorder of photoreceptor degeneration with a later onset of progressive pigmentary retinopathy.  It is described in some cases as a typical retinitis pigmentosa.  The ERG is abnormal in all patients even if the pigmentary pattern is atypical for RP.  Rod responses are usually absent while the cone b-wave implicit time is delayed.  The degree of photoreceptor damage is variable, however.  Extended retinal function among younger patients suggest that the ‘on-pathway’ evolving synapses in the outer plexiform layer among photoreceptors, bipolar cells, and horizontal cells is severely dysfunctional.

Systemic Features: 

This is a multisystem disorder, often diagnosed in the neonatal period by the presence of severe encephalopathy with hypotonia, hyporeflexia, and poor feeding.  Failure to thrive, marked psychomotor retardation, delayed development, growth retardation, and ataxia become evident later in those who survive.  Cerebellar and brainstem atrophy with a peripheral neuropathy can be demonstrated during late childhood.  Some older patients have a milder disease, often with muscle atrophy and skeletal deformities such as kyphoscoliosis and a fusiform appearance of the digits.  Maldistribution of subcutaneous tissue is often seen resulting in some dysmorphism, especially of the face.  Hypogonadism and enlargement of the labia majora are commonly present.  Some patients have evidence of hepatic and cardiac dysfunction which together with severe infections are responsible for a 20% mortality rate in the first year of life.

Genetics

This is one of a group of genetically (and clinically) heterogeneous autosomal recessive conditions caused by gene mutations that result in enzymatic defects in the synthesis and processing of oligosaccharides onto glycoproteins. This type (Ia) is the most common.   The mutation lies in the PMM2 gene (16p13.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Most children require tube feeding with nutritional supplements.  The risk of systemic infections is high.  Those patients who survive into the second decade and beyond may require orthopedic procedures and are confined to wheelchairs.  Physical, occupational, and speech therapy along with parental support are important.

References
Article Title: 

Retinitis Pigmentosa 1

Clinical Characteristics
Ocular Features: 

Night blindness, the predominant presenting symptom, is often noted in the first decade of life but may not be a significant complaint until the third decade.  Concentric peripheral field loss likewise follows a similar timeline.  ERG responses progressively decrease in amplitude and may become undetectable in the second decade.  The retinal disease progresses relentlessly, albeit slowly, as the result of photoreceptor degeneration and most patients have severe visual handicaps by midlife but there is considerable clinical variation.  The pigmentary retinopathy is typical for classical retinitis pigmentosa with vascular attenuation, perivascular bone-spicule pigment clumping, optic atrophy, and generalized retinal atrophy with relative sparing of the macula early in the disease.  Lens opacities in late stages of the disease are common.

Systemic Features: 

No systemic disease is associated with the ocular disorder caused by mutations in RP1.

Genetics

Multiple heterozygous, homozygous, and compound heterozygous mutations in the RP1 gene (8q12.1) sometimes called the oxygen-regulated photoreceptor protein 1 or ORP1 gene are responsible for this disorder.  The protein product is active specifically in retinal photoreceptors.  Retinitis pigmentosa 1 is generally considered to be an autosomal dominant disorder and accounts for 5-7% of dominantly inherited RP disease.  However, recent reports suggest that some mutations in RP1 are responsible for familial cases transmitted in an autosomal recessive pattern in which the clinical disease is more severe. 

More than 20 different mutant genes have been associated with autosomal dominant RP but many cases lack a family history suggesting additional genetic heterogeneity remains.  Reduced penetrance and variable expressivity characteristic of genetic disease likely contributes to the clinical heterogeneity as well.  For more about autosomal dominant retinitis pigmentosa, see Retinitis Pigmentosa, AD (180380, 268000).  

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

Photoreceptor transplantation has been tried in a number of patients without improvement in central vision or interruption in the rate of vision loss.  Longer term results are needed.  Resensitizing photoreceptors with halorhodopsin using archaebacterial vectors shows promise in mice.  High doses of vitamin A palmitate slow the rate of vision loss but plasma levels and liver function need to be checked at least annually.  Oral acetazolamide can be helpful in reducing macular edema.

Low vision aids and mobility training can be facilitating for many patients.  Cataract surgery may restore several lines of vision at least temporarily.

Several pharmaceuticals should be avoided, including isotretinoin, sildenafil, and vitamin E.

References
Article Title: 

Retinitis Punctata Albescens

Clinical Characteristics
Ocular Features: 

Uniform white dots are symmetrically distributed in the midportion and periphery of the retina but the central portion of the macula is usually relatively spared in early stages of the disease.  These flecks are present in the first decade of life increasing in density and covering larger areas of the retina in older individuals.  Difficulties with night vision are also noted early and visual acuity may be compromised, in the range of 20/40.  By the fifth and sixth decades there may be retinal pigment atrophy in the midperiphery and this eventually progresses to geographic atrophy of the macular RPE as the visual field becomes more constricted.  The fundus in older individuals resembles that seen in retinitis pigmentosa with retinal vascular attenuation, frank bone spicule pigmentation, macular disease, and pallor of the optic nerves with significant loss of vision.  The ERG shows reduction in scotopic responses and mild reductions in photopic amplitudes.

This form of flecked retina is sometimes considered to be a variant of fundus albipunctatus (136880).  In favor of this argument are the observations in families in which some young members have the fundus picture of fundus albipunctatus (136880) while older ones with more advanced disease have all of the features of retinitis punctata albescens.  Also supportive is the fact that mutations in RLBP1 have been identified in both conditions.  

However, many individuals with fundus albipunctatus (136880) are described as having a stable disease with night blindness as the major symptom while many patients reported with retinitis albescens clearly have a more progressive and more serious disease with a fundus picture in late stages resembling retinitis pigmentosa.  The relationship of these two conditions should become clearer once we learn more about the natural history of these rare disorders.

Systemic Features: 

No systemic abnormalities have been reported.

Genetics

This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in RLBP1 (15q26.1).  Parental consanguinity is frequently present.  Mutations in the same gene are also responsible for Bothnia type retinal dystrophy (607475), fundus albipunctatus (136880), and occasional patients with classical retinitis pigmentosa. 

Some authors consider retinitis punctata albescens to have an autosomal dominant pattern of transmission, perhaps based on the presence of white spots in the retina of parents.  However, heterozygotes are always asymptomatic.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available.

References
Article Title: 

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

Fundus Albipunctatus

Clinical Characteristics
Ocular Features: 

This disorder is often considered to belong to the category of retinal disease known as flecked retina syndrome.  Further, the nomenclature is not standardized and varying names have been attached to the more or less characteristic fundus picture consisting of uniformly distributed small yellow-white dots in the retina.  These tend to be concentrated in the midperiphery.  The macula usually is not involved in young people although ERG evidence suggests some worsening of cone dysfunction with age and central acuity may be decreased in midlife.  Frank macular degeneration has been seen clinically .  Delayed dark adaptation can be demonstrated with delays in recovery of rod and cone function.  Patients complain of night blindness beginning in childhood with little evidence of progression.

The disease known as retinitis punctata albescens (136880) may or may not be a unique disorder.  It is sometimes grouped with fundus albipunctatus while others consider it to be a separate entity.  Evidence for its uniqueness is based on the progressive nature of field loss and the presence of pigmentary changes and retinal vascular attenuation which are not found in fundus albipunctatus.  Further, the scotopic ERG waveforms usually do not regenerate.  More discriminating studies, especially genotyping, will likely provide additional information.  It would also be useful to have additional follow-up information on families. 

Systemic Features: 

No systemic disease is associated.

Genetics

Fundus albipunctatus is a genetically heterogeneous disorder.  Mutations in two genes, PRPH2 (6p21.1) and RDH5 (12q13.2) have been found among families.  The inheritance pattern for families with mutations in PRPH2 is consistent with autosomal dominant inheritance while mutations in RDH5 result in an autosomal recessive pattern.  Mutations in RLBP1 have also been found in some families.

Gene studies so far have not been helpful in discriminating between fundus albipunctatus and retinitis punctata albescens (136880).  For example, RLBP1 mutations have been identified among members of the same kindred having the clinical diagnosis of retinitis punctata albescens (136880) among older individuals while younger patients had features of fundus albipunctatus.  Further, the latter disorder has also been described among families with mutations in PRPH2 and RHO hinting at further genetic heterogeneity.

A similar clinical picture may be seen in Bietti crystalline corneoretinopathy (210370), Bardet-Biedl syndrome (209900), and hyperoxaluria (259900).  More information on flecked retina syndromes may be found at Flecked Retina Syndromes.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available to restore full receptor cell function.  However, high oral doses of beta-carotene may lead to an improvement in night blindness. Low vision aids could be beneficial when central acuity is damaged.

References
Article Title: 

Chorioretinopathy, Ataxia, and Hypogonadism

Clinical Characteristics
Ocular Features: 

The retinal pigment epithelium changes may be seen as early as the first decade of life with pigment deposition resembling bone spicules.  These changes as well as atrophy of the choriocapillaris are most apparent in the posterior pole and extend into the midperiphery.  Retinal vessels may be attenuated.  Progressive loss of vision, dyschromatopsia, and photophobia are the primary ocular symptoms. Night blindness and constricted visual fields are noted by some patients.  The ERG shows subnormal and sometimes absent photopic and scotopic responses.  Nystagmus is present in more than half of individuals. 

Systemic Features: 

Difficulties with balance, intention tremors, and scanning speech are evident in adolescence or early adult life.  Cerebellar ataxia is present in nearly 40 percent of individuals.  However, there is marked variability in the rate of progression.  Many patients have atrophy of the superior and dorsal areas of the cerebellar vermis and atrophy of the cerebellar hemispheres as noted on MRIs. Hypogonadotrophic hypogonadism is a feature with delayed puberty noted in 26 percent.  In the absence of exogenous hormone administration, secondary sexual characteristics fail to develop.

Genetics

Autosomal recessive inheritance has been suggested on the basis of consanguinity in three families, multiple affected sibs born to normal parents, and a 1:1 sex ratio.  Homozygous and compound heterozygous mutations in PNPLA6 (19p13.2) have been found in several patients.

Mutations in PNPLA6 occur in other conditions including a form of Bardet-Biedl Syndrome (209900), and Trichomegaly Plus Syndrome (275400), in this database.

 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

The use of appropriate hormones can stimulate the development of normal secondary sexual characteristics and may restore reproductive function.   At least two female patients gave birth to a child following hormone substitution.

Low vision aids could be helpful in selected patients.

References
Article Title: 

Boucher-Neuhäuser syndrome: cerebellar degeneration, chorioretinal dystrophy and hypogonadotropic hypogonadism: two novel cases and a review of 40 cases from the literature

Tarnutzer AA, Gerth-Kahlert C, Timmann D, Chang DI, Harmuth F, Bauer P, Straumann D, Synofzik M. Boucher-Neuhauser syndrome: cerebellar degeneration, chorioretinal dystrophy and hypogonadotropic hypogonadism: two novel cases and a review of 40 cases from the literature. J Neurol. 2014 Oct 31. [Epub ahead of print].

PubMed ID: 
25359264

PNPLA6 mutations cause Boucher-Neuhauser and Gordon Holmes syndromes as part of a broad neurodegenerative spectrum

Synofzik M, Gonzalez MA, Lourenco CM, Coutelier M, Haack TB, Rebelo A, Hannequin D, Strom TM, Prokisch H, Kernstock C, Durr A, Schols L, Lima-Martinez MM, Farooq A, Schule R, Stevanin G, Marques W Jr, Zuchner S. PNPLA6 mutations cause Boucher-Neuhauser and Gordon Holmes syndromes as part of a broad neurodegenerative spectrum. Brain. 2013 Dec 19. [Epub ahead of print].

PubMed ID: 
24355708

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