pigmentary retinopathy

Hypotrichosis with Juvenile Macular Degeneration

Clinical Characteristics
Ocular Features: 

Macular dystrophy usually becomes symptomatic before the second decade of life but retinal evidence of macular degeneration can be seen in the first decade.   EOG is usually normal while the ERG responses are decreased early and with time decrease further in amplitude.  Pattern reversal VEPs are significantly subnormal even while vision is relatively good.  Visual acuity decreases slowly in spite of significant deterioration of cone- and rod-mediated retinal function.  Retinal pigmentary changes consisting of irregular clumping and areas of hypopigmentation are evident in the macular and perimacular areas and sometimes beyond.  Most patients eventually become blind. 

Systemic Features: 

Scalp hair loss occurs during the first months of life but the alopecia does not affect eyebrows or eyelashes unlike that seen in the EEM disorder (225280)  which in addition has digital and dental anomalies.  Partial regrowth may occur during puberty.  Light and electron microscopy of hair shafts may reveal pili torti, longitudinal ridging with scaling, and fusiform beading but these are not present in all patients. 

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the CDH3 gene located at 16q22.1.

EEM syndrome (225280) is an allelic disorder with similar hair and retinal features plus dental, digital and limb anomalies.  The hypotrichosis also involves the eyebrows and eyelashes in this disorder, however. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no known treatment for this disorder. 

References
Article Title: 

Pierson Syndrome

Clinical Characteristics
Ocular Features: 

Microcoria is the most consistent ocular feature but is not present in some families.  It is congenital and sometimes seen with iris hypoplasia.  Glaucoma and lens opacities (including posterior lenticonus sometimes) are present in one-fourth of patients.  Corneal size varies with some patients having apparent macrocornea which can lead to the mistaken diagnosis of buphthalmos.  Pigment mottling and clumping is common in the retina and the ERG can show changes characteristic of cone-rod dystrophy.  Retinal thinning is often present as well.  Non-rhegmatogenous retinal detachments occur in 24% of patients and optic atrophy is seen in some individuals.  There is considerable interocular, intrafamilial, and interfamilial variability in these signs. 

Systemic Features: 

The primary and most consistent systemic problem is progressive renal disease. Congenital nephrotic syndrome with proteinuria, hypoalbuminemia and hypertension is characteristic.  Renal failure eventually occurs although the rate of progression varies. Most patients require a renal transplant for end-stage kidney disease in the first decade of life.  Kidney histology shows glomerulosclerosis, peritubular scarring, and diffuse mesangial sclerosis.  Hypotonia and muscle weakness are sometimes present and congenital myasthenia has been reported.  Severe global psychomotor retardation is common and many infants never achieve normal milestones. 

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the LAMB2 gene located at 3p21.  The normal gene encodes laminin beta-2 that is strongly expressed in intraocular muscles which may explain the hypoplasia of ciliary and pupillary muscles in Pierson syndrome.  Mutations in this gene are often associated with nephronophthisis but ocular abnormalities are not always present. 

Microcoria is also a feature of the autosomal dominant ocular condition known as congenital microcoria (156600).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Kidney replacement can restore renal function.  Glaucoma, cataracts, and retinal detachments require the usual treatment but patient selection is important due to the neurological deficits.  Lifelong monitoring is essential. 

References
Article Title: 

Ocular findings in a case of Pierson syndrome with a novel mutation in laminin ß2 gene

Arima M, Tsukamoto S, Akiyama R, Nishiyama K, Kohno RI, Tachibana T, Hayashida A, Murayama M, Hisatomi T, Nozu K, Iijima K, Ohga S, Sonoda KH. Ocular findings in a case of Pierson syndrome with a novel mutation in laminin ss2 gene. J AAPOS. 2018 Aug 16. pii: S1091-8531(18)30497-X. doi: 10.1016/j.jaapos.2018.03.016. [Epub ahead of print].

PubMed ID: 
30120985

Ophthalmological aspects of Pierson syndrome

Bredrup C, Matejas V, Barrow M, Bl?deghov?deg K, Bockenhauer D, Fowler DJ, Gregson RM, Maruniak-Chudek I, Medeira A, Mendon?ssa EL, Kagan M, Koenig J, Krastel H, Kroes HY, Saggar A, Sawyer T, Schittkowski M, Swietli?Nski J, Thompson D, VanDeVoorde RG, Wittebol-Post D, Woodruff G, Zurowska A, Hennekam RC, Zenker M, Russell-Eggitt I. Ophthalmological aspects of Pierson syndrome. Am J Ophthalmol. 2008 Oct;146(4):602-611.

PubMed ID: 
18672223

Cone-Rod Dystrophies, AD and AR

Clinical Characteristics
Ocular Features: 

Cone-rod dystrophies (CRD) are a group of pigmentary retinopathies that have early and important changes in the macula.  Cone dysfunction occurs first and is often followed by rod photoreceptor degeneration.

Common initial symptoms are decreased visual acuity, dyschromatopsia, and photophobia which are often noted in the first decade of life.  Night blindness occurs later as the disease progresses.  A fine nystagmus is also common. Visual field defects include an initial central scotoma with patchy peripheral defects followed by larger defects in later stages.  The fundus exam can be normal initially, but is followed by pigmentary bone spicule changes, attenuation of retinal vessels, waxy pallor of the optic disc and retinal atrophy.  A ring maculopathy surrounding the fovea is usually evident.  The ERG first reveals photopic defects and later scotopic changes.  Fluorescein angiography and fundus autofluorescence generally reveal atrophic retinopathy.  Many patients eventually become legally blind as the disease progresses and some end up with no light perception.

Cone-rod dystrophies are a group of disorders separate from rod-cone dystrophies where the primary defect is in the rod photoreceptors with typical pigmentary changes in the peripheral retina. The progression of vision loss is generally slower in rod-cone dystrophies. Cone dystrophies comprise another group of disorders with exclusive cone involvement in which the macula often has a normal appearance in association with loss of central acuity.

Systemic Features: 

No systemic disease is associated with simple cone-rod dystrophies.  See below for syndromal disorders with cone-rod dystrophy. 

Genetics

Non-syndromic cone-rod dystrophies can be either autosomal dominant, autosomal recessive or X-linked and are caused by defects in at least 17 different genes.  This database entry discusses only the autosomal disorders.  See X-linked cone-rod dystrophies in a separate entry.

Cone-rod dystrophies inherited in an autosomal dominant pattern include:

CORD2 (120970) is caused by mutations in CRX at 19q13.3, a homeobox gene responsible for the development of photoreceptor cells.  These are responsible for 5-10% of autosomal dominant cone-rod dystrophy cases (602225) and can also cause one type (LCA7) of Leber congenital amaurosis (602225) and a late-onset retinitis pigmentosa phenotype.

CORD5 (600977) is caused by mutations in the PITPNM3 gene at 17p13.1. 

CORD6 (601777) is caused by a mutation in GUCY2D in a similar location on chromosome 17. 

CORD7 (603649) is caused by mutations in RIMS1 at 6q12-q13.

Mutations in AIPL1 (604392), located in the same region, usually causes a form of Leber congenital amaurosis (LCA4) as well as retinitis pigmentosa (604393) but has also been reported in a cone-rod pigmentary retinopathy.

CORD11 (610381) is caused by mutations in RAXL1 (19p13.3).

CORD12 (612657) results from mutations in the PROM1 gene (4p15.3).

Mutations in the gene GUCA1A on chromosome 6p21.1 causes CORD14 (602093).

An as yet unclassified autosomal dominant type of cone-rod dystrophy has recently been localized to 10q26.

Cone-rod dystrophies inherited in an autosomal recessive pattern include:

Mutations in ABCA4 at 1p21-p13 is responsible for 30-60% of cases of autosomal recessive CRD (CORD3; 604116) .  ABCA4 is also known to cause autosomal recessive Stargardt disease.

CORD8 (605549) has been found in a single consanguineous family and the mutation localized to 1q12-q24.

ADAM9 (602713) at 8p11 and 8p11.23 contains mutations that have been shown to cause autosomal recessive CORD9 in several consanguineous families.

Mutations in RPGRIP1 (14q11) are responsible for CORD13 (608194).

The CDHR1 gene (10q23.1) contains mutations that cause CORD15 (613660).

Other autosomal CRD disorders are CORD1 (600624) described in a single individual and possibly those due to mutations in HRG4 at 17q11.2 (604011).

Syndromal cone-rod dystrophies:

Cone-rod dystrophy may also be associated with other syndromes, such as Bardet-Biedl syndrome (209900), or spinocerebellar ataxia Type 7 (164500), autosomal recessive amelogenesis imperfecta with cone-rod dystrophy or Jalili syndrome (217080), neurofibromatosis type I (162200), and hypotrichosis with juvenile macular dystrophy and alopecia (601553).  Metabolic disorders associated with cone-rod dystrophy include Refsum disease with phytanic acid abnormality (266500) and Alport syndrome (301050). 

Cone-Rod Dystrophy 19 (615860) has been associated with male infertility as the result of mutations in TTLL5 affecting both photoreceptors and sperm.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for these dystrophies but red-tinted lenses provide comfort and may sometimes improve acuity to some extent.  Low vision aids can be helpful. 

References
Article Title: 

A novel locus for autosomal dominant cone-rod dystrophy maps to chromosome 10q

Kamenarova K, Cherninkova S, Romero Dur?degn M, Prescott D, Vald?(c)s S?degnchez ML, Mitev V, Kremensky I, Kaneva R, Bhattacharya SS, Tournev I, Chakarova C. A novel locus for autosomal dominant cone-rod dystrophy maps to chromosome 10q. Eur J Hum Genet. 2012 Aug 29. doi: 10.1038/ejhg.2012.158. [Epub ahead of print]

PubMed ID: 
22929024

Cone rod dystrophies

Hamel CP. Cone rod dystrophies. Orphanet J Rare Dis. 2007 Feb 1;2:7. Review.

PubMed ID: 
17270046

Retinitis Pigmentosa, AR

Clinical Characteristics
Ocular Features: 

The term retinitis pigmentosa is applied to a large group of disorders with great clinical and genetic heterogeneity.  The ocular disease is characterized by night blindness, field constriction, and pigmentary changes in the retina.  The latter is sometimes described as having a ‘bone corpuscle’ appearance with a perivascular distribution.  A ring scotoma is usually evident.  Age of onset and rate of progression is highly variable, even within families.  The rods are impacted early but cone deterioration with loss of central vision usually follows.  Some patients complain of dyschromatopsia and photophobia.  The ERG generally documents this progression but the mfERG shows wide variations in central cone functioning.  Legal blindness is common by the 5thdecade of life or later.  The course of clinical and ERG changes is more aggressive in the X-linked form than in the autosomal dominant disease.  The final common denominator for all types is first rod and then cone photoreceptor loss through apoptosis.

As many as 50% of patients develop posterior subcapsular cataracts.  The vitreous often contains cells and particulate debris.   Retinal arterioles are often attenuated and the optic nerve may have a waxy pallor, especially late in the disease.  Occasional patients have cysts in the macula.  Some patients experience continuous photopsia. 

Systemic Features: 

The ‘simple’ or nonsyndromal type of RP described here has no systemic features.  However, the retinopathy is seen in a number of syndromes and, of course, in some infectious diseases as well.  It is more accurate to label the fundus finding as 'pigmentary retinopathy' in such cases.

Genetics

A significant proportion of RP cases occur sporadically, i.e., without a family history.  Mutations in more than 30 genes cause autosomal recessive RP disorders and these account for more than half of all cases of retinitis pigmentosa.  More than 100 mutations have been identified in the RHO gene (3q21-q24) alone.  Mutations in some genes cause RP in both autosomal recessive and autosomal dominant inheritance patterns.  Compound heterozygosity is relatively common in autosomal recessive disease.  See OMIM 268000 for a complete listing of mutations.

Many genes associated with retinitis pigmentosa have also been implicated in other pigmentary retinopathies.  In addition, numerous phenocopies occur, caused by a variety of drugs, trauma, infections and numerous neurological disorders.  To make diagnosis even more difficult, the fundus findings and ERG responses in nonsyndromic RP in most patients are too nonspecific to be useful for classification. Extensive systemic and ocular evaluations are important and should be combined with genotyping in both familial and nonfamilial cases to determine the diagnosis and prognosis. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Photoreceptor transplantation has been tried in 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 Pigmentosa, AD

Clinical Characteristics
Ocular Features: 

Retinitis pigmentosa is a large group of disorders with great clinical and genetic heterogeneity.  The ocular disease is characterized by night blindness, field constriction, and pigmentary changes in the retina.  The later may have a 'bone corpuscle' appearance with a perivascular distribution.  A ring scotoma is sometimes evident.  Age of onset and rate of progression is highly variable, even within families.  The rods are impacted early but cone deterioration with loss of central vision usually follows.  Some patients complain of dyschromatopsia and photophobia.  The ERG generally documents this progression but the mfERG shows wide variations in central cone functioning.  Legal blindness is common by the 5thdecade of life or later.  The course of clinical and ERG changes is more aggressive in the X-linked form than in the autosomal dominant RHO disease.  The final common denominator for all types is first rod and then cone photoreceptor loss through apoptosis.

As many as 50% of patients develop posterior subcapsular cataracts.  The vitreous often contains cells and particulate debris.   Retinal arterioles are often attenuated and the optic nerve may have a waxy pallor, especially late in the disease.  Occasional patients have cysts in the macula.  Some patients experience continuous photopsia.  

Systemic Features: 

The 'simple' or nonsyndromal type of RP described here has no systemic features.  However, the retinopathy is seen in a number of syndromes and, of course, in trauma and in some infectious diseases as well. 

Genetics

A significant proportion of RP cases occur sporadically, i.e., without a family history.  Mutations in more than 25 genes cause autosomal dominant RP disorders and these account for about one-third of all cases of retinitis pigmentosa but there are many more specific mutations.  More than 100 have been identified in the RHO gene (3q21-q24) alone, for example.  Mutations in some genes cause RP in both autosomal recessive and autosomal dominant inhritance patterns.  See OMIM 268000 for a complete listing of mutations.

Many genes associated with retinitis pigmentosa have also been implicated in other pigmentary retinopathies.  In addition numerous phenocopies occur, caused by a variety of drugs, trauma, infections and numerous neurological disorders.  To make diagnosis even more difficult, the fundus findings and ERG responses in nonsyndromic RP in most patients are too nonspecific to be useful for classification. Extensive systemic and ocular evaluations are important and should be combined with genotyping in both familial and nonfamilial cases to determine the diagnosis and prognosis. 

For autosomal dominant retinitis pigmentosa resulting from mutations in RP1, see Retinitis Pigmentosa 1 (180100). 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Photoreceptor transplantation has been tried in 8 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.  The use of oral and systemic carbonic anhydrase inhibitors 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 Pigmentosa 3, X-Linked

Clinical Characteristics
Ocular Features: 

Retinitis pigmentosa is a large group of disorders with great clinical and genetic heterogeneity.  The ocular disease is characterized by night blindness, field constriction, and pigmentary changes in the retina.  The later may have a ‘bone corpuscle’ appearance with a perivascular distribution.  A ring scotoma is sometimes evident.  Age of onset and rate of progression is highly variable, even within families.  In this, an X-linked form of the disease, the first symptoms often appear early in the second decade of life.  The rods are impacted early but cone deterioration with loss of central vision usually follows.  Some patients complain of dyschromatopsia and photophobia.  The ERG generally documents this progression but the mfERG shows wide variations in central cone functioning.  Legal blindness is common by the 4thor 5thdecades of life.  The course of clinical and ERG changes is more aggressive in the X-linked form than in autosomal dominant retinitis pigmentosa disease resulting from RHO mutations.  The final common denominator for all types is first rod and then cone photoreceptor loss through apoptosis.

Up to 50% of adults develop cataracts beginning in the posterior subcapsular area.  The vitreous often contains cells and some patients have cystoid macular edema.  A waxy pallor of the optic nerve is sometimes present especially in the later stages of the disease.

Female carriers generally are asymptomatic but may also have severe RP.  Occasionally they have an unusual tapetal reflex consisting of a ‘beaten metal’ appearance or sometimes scintillating, golden patches. 

Systemic Features: 

There is no systemic disease in ‘simple’ or non-syndromic retinitis pigmentosa but pigmentary retinopathy is associated with a number of syndromes (syndromal RP) e.g.,  Usher syndromes, Waardenburg syndrome, Alport syndrome, Refsum disease, Kerns-Sayre syndrome, abetalipoproteinemia, neuronal ceroid lipofuscinosis, mucopolysaccharidoses types I, II, III, and Bardet-Biedl syndromes. 

The RPGR gene is important to the normal function of cilia throughout the body.  For this reason disorders resulting from RPGR mutations such as CORDX1 (304020) and this one are sometimes classified as primary ciliary dyskinesias or ciliopathies.  The gene products of the RPGR gene, for example, are localized to connecting cilia of the outer segments of rods and cones and in motile cilia in the airway epithelia.  A subset of families with RP3 have chronic and recurrent upper respiratory infections including sinusitis, bronchitis, pulmonary atelectasis, and otitis media (300455) similar to that seen in the immotile cilia syndrome (244400).  Female carriers in these families have few retinal changes but may suffer recurrent and severe upper respiratory infections similar to hemizygous males.  Severe hearing loss also occurs in both sexes with the RPGR mutations and there is some evidence that this may be a primary sensorineural problem, perhaps in addition to conductive loss from recurrent otitis media.

Genetics

Mutations in more than 100 genes may be responsible for retinitis pigmentosa but sporadic disease occurs as well.  Between 5 and 10% of individuals have X-linked disease.  Perhaps 70% of X-linked RP is caused by mutations in RPGR (Xp11.4) as in this condition.  The same gene is mutant in one form of X-linked cone-rod dystrophy (CORDX1; 304020). These  disorders are sometimes considered examples of X-linked ocular disease resulting from a primary ciliary dyskinesia (244400).

Another form of X-linked RP (RP2) with more choroidal involvement is caused by mutations in the RP2 gene (312600 ; Xp11.23). 

Many genes associated with retinitis pigmentosa have also been implicated in other pigmentary retinopathies.  In addition numerous phenocopies occur, caused by a variety of drugs, trauma, infections and numerous neurological disorders.  To make diagnosis even more difficult, the fundus findings and ERG responses in nonsyndromic RP in most patients are too nonspecific to be useful for classification. Extensive systemic and ocular evaluations are important and should be combined with genotyping in both familial and nonfamilial cases to determine the diagnosis and prognosis. 

Treatment
Treatment Options: 

Photoreceptor transplantation has been tried in 8 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: 

Spinocerebellar Ataxia 7

Clinical Characteristics
Ocular Features: 

Pigmentary changes in the retina are somewhat variable but often begin with a granular appearance in the macula and spread into the periphery.  The macula often becomes atrophic and dyschromatopsia is common.   Retinal thinning is evident, especially in the macula.  Decreased visual acuity and loss of color vision are early symptoms and the ERG shows abnormalities of both rod and cone function.  External ophthalmoplegia without ptosis is a frequent sign.  Most adults and some children eventually are blind. 

Systemic Features: 

Symptoms of developmental delay and failure to thrive may appear in the first year of life followed by loss of motor milestones.  Dysarthria and ataxia are nearly universal features while pyramidal and extrapyramidal signs are more variable.  This can be a rapidly progressive disease and children who develop symptoms by 14 months are often deceased before two years of age.  However, adults with mild disease can survive into the 5th and 6th decades.  Peripheral neuropathy with sensory loss and motor deficits are usually present to some degree but the range of clinical disease is wide.  Cognitive decline and some degree of dementia occur sometimes. 

Genetics

Spinocerebellar ataxia 7 is caused by expanded trinucleotide repeats (CAG) in the ATXN7 gene (3p21.1-p12) and inherited in an autosomal dominant pattern.  The number of repeats is variable and correlated with severity of disease.  Most patients with 36 or more repeats have significant disease. This disorder is sometimes classified as a progressive cone-rod dystrophy.  It is sometimes referred to as olivopontocerebellar atrophy type III or OPCA3.

This disorder exhibits genetic anticipation especially with paternal transmission as succeeding generations often have earlier onset with more severe and more rapidly progressive disease. This is explained by the fact that younger generations tend to have a larger number of repeats and sometimes the diagnosis is made in children before the disease appears in parents or grandparents.

Spinocerebellar ataxia 1 (164400) is a similar autosomal dominant disorder with many of the same clinical and genetic features.  It is caused by excess CAG repeats on the ATXN1 gene on chromosome 6. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No effective treatment is known for the disease.  Low vision aids and mobility training may be useful in early stages. 

References
Article Title: 

Stargardt Disease

Clinical Characteristics
Ocular Features: 

Stargardt disease or fundus flavimaculatus is a progressive form of juvenile macular degeneration with considerable clinical and genetic heterogeneity.  It may be considered a syndromal cone-rod dystrophy because of overlapping clinical features such as loss of color vision and photophobia in some patients.  Adding to the confusion is the fact that mutations in at least 4 genes are responsible for similar clinical characteristics.  Due to the lack of diagnostic distinctions and the wide range of nonspecific clinical manifestations, Stargardt disease and fundus flavimaculatus are discussed here as a single entity.

Onset of vision loss is often noted late in the first decade of life usually with rapid progression.  However, some patients are asymptomatic until much later, even into the fifth decade.  There is evidence that patients with an early onset have a worse prognosis compared to those with a later onset.  Nevertheless, large series of patients contain at least 23% with 20/40 or better acuity, about 20% with 20/50 -20/100, 55% have 20/200-20/400, and a small number have vision less than 20/400. 

Some color discrimination is lost and photophobia may be a complaint.  Dark adaptation is prolonged but nightblindness does not usually occur and peripheral visual fields are normal.  The posterior pole characteristically has yellowish pisciform, round, and linear subretinal lipofuscin deposits which often extend to the equator.  These may be present before clinical symptoms are present.  Histopathology reveals accumulations of this material in RPE cells.  Atrophy of the RPE in the same region is often visible as well but these changes may be subtle initially.  Some patients have peripheral pigment clumping which may resemble the bone spicule configuration seen in retinitis pigmentosa.  However, retinal vessel caliber is normal in Stargardt disease.  Extensive macular disease can be associated with temporal pallor of the optic nerve.  The ERG shows reduced photopic responses with normal or near normal scotopic tracings.  Fluorescein angiography often reveals more extensive disease than seen on fundoscopy.  Window defects are common in the macula where the RPE is atrophied.  The flecks may be hypo- or hyperfluorescent.  Over 50% of patients have patches of angiographically dark choroid in the posterior pole which is thought to be secondary to transmission blockage by lipofuscin accumulations in the RPE. 

Systemic Features: 

None.

Genetics

This group of disorders may be caused by mutations in at least 4 genes.  These are: STGD1 (248200) caused by mutations in the ABCA4 gene located at 1p22.1, or in CNGB3 (262300) (8q21-q22) which also is mutant in achromatopsia 3 (ACHM3), STGD3 (605512) caused by mutations in the ELOVL4 gene at 6q14, and STGD4 (603786) caused by a mutation in PROM1 on chromosome 4p.  STGD4 and STGD3 disease have been found in pedigrees consistent with autosomal dominant inheritance but STGD1 disease seems to be inherited in an autosomal recessive pattern.

Genotyping is necessary for accurate diagnostic determinations.  In particular, a few patients clinically found to have typical areolar macular dystrophy, retinitis pigmentosa, juvenile macular degeneration, and cone dystrophies have been reported in association with several of these mutations and reports have also associated Stargardt disease with mutations in RDS.

A single family with a brother and sister with Stargardt disease and neurological malformations has been reported (612948).  Both had developmental delays associated with absence or hypoplasia of the corpus callosum, upslanted lid fissures, 'flared eyebrows', a broad nasal tip, a broad face with a pointed chin, and sensorineural hearing loss along with mild digital malformations.  Evidence of macular degeneration was seen at age 7 years and vision in both individuals was in the 20/100-20/200 range. No associated locus or mutation has been identified.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for this disorder but low vision aids can be helpful especially in the early stages of the disease.

Isotretinoin has been shown to slow the accumulation of lipofuscin pigments in mice but its role in human Stargardt disease has not been reported.  Trials using stem cells are underway with encouraging early results.

References
Article Title: 

Comprehensive analysis of patients with Stargardt macular dystrophy reveals new genotype-phenotype correlations and unexpected diagnostic revisions

Zaneveld J, Siddiqui S, Li H, Wang X, Wang H, Wang K, Li H, Ren H, Lopez I, Dorfman A, Khan A, Wang F, Salvo J, Gelowani V, Li Y, Sui R, Koenekoop R, Chen R. Comprehensive analysis of patients with Stargardt macular dystrophy reveals new genotype-phenotype correlations and unexpected diagnostic revisions. Genet Med. 2014 Dec 4.  [Epub ahead of print].

PubMed ID: 
25474345

Bornholm Eye Disease

Clinical Characteristics
Ocular Features: 

This is primarily a disorder of high myopia but with additional features.  The optic nerve head is moderately hypoplastic and RPE throughout the posterior pole is said to be thinner than normal.  The males also have deuteranopia of a stationary nature and the disorder can also be considered a form of stationary cone dysfunction.  Photophobia and nystagmus are not present.  The ERG demonstrates reduced flicker function with abnormal photopic responses.  Myopia is likely congenital as it has been found in children from 1.5-5 years of age.

The original families reported with this disorder originated on the Danish island of Bornholm from which the eponym is derived.  However, a subsequent American family of Danish descent from nearby islands was found but the males were protanopes.  All affected males had a temporal conus of the optic nerve as well as thinning of the RPE in the posterior pole.  Visual acuity ranged from 20/20 to 20/40 with myopia of minus 10-18 diopters.  No macular disease was visible, no vitreous changes were seen, and none of the subjects had a retinal detachment. There was no evidence of progression in clinical signs over a period of 5 years.  The ERG showed normal scotopic rod function but cone responses were abnormal.  All carrier females and unaffected individuals had normal ERGs and color vision. 

Systemic Features: 

No systemic disease has been associated with this disorder. 

Genetics

This is an X-linked disorder that maps to Xq28 but no gene mutation has been identified.  A form of X-linked high myopia (MYP1) (310460) maps to the same region. 

Pedigree: 
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

No treatment is available.

References
Article Title: 

X-linked high myopia associated with cone dysfunction

Young TL, Deeb SS, Ronan SM, Dewan AT, Alvear AB, Scavello GS, Paluru PC, Brott MS, Hayashi T, Holleschau AM, Benegas N, Schwartz M, Atwood LD, Oetting WS, Rosenberg T, Motulsky AG, King RA. X-linked high myopia associated with cone dysfunction. Arch Ophthalmol. 2004 Jun;122(6):897-908.

PubMed ID: 
15197065

X-linked myopia: Bornholm eye disease

Schwartz M, Haim M, Skarsholm D. X-linked myopia: Bornholm eye disease. Linkage to DNA markers on the distal part of Xq. Clin Genet. 1990 Oct;38(4):281-6.

PubMed ID: 
1980096

X-linked myopia in Danish family

Haim M, Fledelius HC, Skarsholm. X-linked myopia in Danish family. Acta Ophthalmol (Copenh). 1988 Aug;66(4):450-6.

PubMed ID: 
3264103

Leber Congenital Amaurosis

Clinical Characteristics
Ocular Features: 

Leber congenital amaurosis is a collective term applied to multiple recessively inherited conditions with early-onset retinal dystrophy causing infantile or early childhood blindness.  There are no established diagnostic criteria.  First signs are usually noted before the age of 6 months.  These consist of a severe reduction in vision accompanied by nystagmus, abnormal pupillary responses, and photophobia.  Ametropia in the form of hyperopia is common.  Keratoconus (and keratoglobus) is frequently found in older children but it is uncertain if this is a primary abnormality or secondary to eye rubbing as the latter is commonly observed.  Repeated pressure on the eye may also be responsible for the relative enophthalmos often seen in these patients.  The ERG is reduced or absent early and permanently.  Final visual acuity is seldom better than 20/400 and perhaps one-third of affected individuals have no light perception.  Some individuals experience a period of vision improvement.

The retina usually has pigmentary changes but these are not diagnostic.  Retinal vessels are generally attenuated.  The RPE may have a finely granulated appearance or, in some cases, whitish dots, and even 'bone spicules'.

Systemic Features: 

A variety of metabolic and physical abnormalities have been reported with LCA but many publications are from the pre-genomic era and the significance of such associations remains uncertain.  Most extraocular signs result from delays in mental development but it is uncertain what role, if any, that visual deprivation plays.  Perhaps 20% of patients are mentally retarded or have significant cognitive deficits.

Genetics

Leber congenital amaurosis is genetically heterogeneous with at least 18 known gene mutations associated with the phenotype.  It is also clinically heterogeneous both within and among families and this is the major obstacle to the delineation of individual clinicogenetic entities.  As more patients are genotyped, it is likely that more precise genotype-phenotype correlations will emerge.  At the present time, however, it is not possible to use clinical findings alone to distinguish individual conditions.

Below are links to the genotypic and phenotypic features of the 19 known types of LCA.  All cause disease in the homozygous or compound heterozygous state. 

LCA type               OMIM#                 Locus              Gene Symbol   

LCA 1                    204000                 7p13.1                 GUCY2D

LCA 2                    204100                 1p31                    RPE65**

LCA 3                    604232                 14q31.3               SPATA7

LCA 4                    604393                 17p13.1               AIPL1

LCA 5                    604537                 6q14.1                 LCA5

LCA 6                    613826                 14q11                  RPGRIP1

LCA 7                    613829                19q13.1                CRX*

LCA 8                    613835                 1q31-q32             CRB1

LCA 9                    608553                 1p36                    NMNAT1

LCA 10                  611755                 12q21                  CEP290

LCA 11                  613837                 7q31.3-q332        IMPDH1

LCA 12                  610612                 1q32.3                 RD3

LCA 13                  612712                 14q24.1               RDH12

LCA 14                  613341                 4q31                    LRAT

LCA 15                  613843                 6p21-31              TULP1

LCA 16                  614186                 2q37                    KCNJ13

LCA 17                  615360                 8q22.1                 GDF6

LCA 18                  608133                 6p21.1                 PRPH2***

It is likely that more mutant genes will be identified since these are found in only about half of patients studied in large series.  

*(Heterozygous mutations in CRX may also cause a cone-rod dystrophy).

**(Mutations in RPE65 has been described as also causing retinitis pigmentosa (RP20; 613794)  with choroidal involvement.)

***Mutations in PRPH2 (RDS) has also been reported to cause retinitis pigmentosa 7, choroidal dystrophy, and vitelliform macular dystrophy (179605) among others.

See also Leber Congenital Amaurosis with Early-Onset Deafness.

Mutations in the GUCY2D gene seem to be the most common being present in about 21% of LCA patients with CRB1 next at 10%.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Until recently, no treatment was available for LCA.  However, results from early clinical trials with adeno-associated virus vector mediated gene therapy for RPE65 mutations in LCA 2 show promise.  Subretinal placement of recombinant  adeno-virus carrying RPE65 complementary DNA results in both subjective and objective improvements in visual function.  Patients generally report subjective improvement in light sensitivity and visual mobility.  Some recovery of rod and cone photoreceptor function has been documented.  Studies have also documented an improvement in visual acuity, size of visual field, pupillary responses, and in the amouunt of nystagmus.  More than 230 patients have now  been treated and improvements seem to be maintained for at least 3 or more years.  However, we have also learned that along with the enzymatic dysfunction of RPE65 that disrupts the visual cycle, there is also degeneration of photoreceptors which continues after treatment and the long term prognosis remains guarded. Multiple phase I clinical trials have demonstrated the safety of this approach and phase III trials are now underway.

It is crucial for patients to be enrolled early in sensory stimulation programs to ensure optimum neural development.  For patients with residual vision, low vision aids can be beneficial.  Vocational and occupational therapy should be considered for appropriate patients.

References
Article Title: 

Mutations in NMNAT1 cause Leber congenital amaurosis and identify a new disease

Koenekoop RK, Wang H, Majewski J, Wang X, Lopez I, Ren H, Chen Y, Li Y,
Fishman GA, Genead M, Schwartzentruber J, Solanki N, Traboulsi EI, Cheng J, Logan
CV, McKibbin M, Hayward BE, Parry DA, Johnson CA, Nageeb M; Finding of Rare
Disease Genes (FORGE) Canada Consortium, Poulter JA, Mohamed MD, Jafri H, Rashid
Y, Taylor GR, Keser V, Mardon G, Xu H, Inglehearn CF, Fu Q, Toomes C, Chen R.
Mutations in NMNAT1 cause Leber congenital amaurosis and identify a new disease
pathway for retinal degeneration. Nat Genet. 2012 Jul 29.
 

PubMed ID: 
22842230

A dominant mutation in RPE65 identified by whole-exome sequencing causes retinitis pigmentosa with choroidal involvement

Bowne SJ, Humphries MM, Sullivan LS, Kenna PF, Tam LC, Kiang AS, Campbell M, Weinstock GM, Koboldt DC, Ding L, Fulton RS, Sodergren EJ, Allman D, Millington-Ward S, Palfi A, McKee A, Blanton SH, Slifer S, Konidari I, Farrar GJ, Daiger SP, Humphries P. A dominant mutation in RPE65 identified by whole-exome sequencing causes retinitis pigmentosa with choroidal involvement. Eur J Hum Genet. 2011 Oct;19(10):1074-81. Erratum in: Eur J Hum Genet. 2011 Oct;19(10):1109.

PubMed ID: 
21654732

Treatment of leber congenital amaurosis due to RPE65 mutations by ocular subretinal injection of adeno-associated virus gene vector: short-term results of a phase I trial

Hauswirth WW, Aleman TS, Kaushal S, Cideciyan AV, Schwartz SB, Wang L, Conlon TJ, Boye SL, Flotte TR, Byrne BJ, Jacobson SG. Treatment of leber congenital amaurosis due to RPE65 mutations by ocular subretinal injection of adeno-associated virus gene vector: short-term results of a phase I trial. Hum Gene Ther. 2008 Oct;19(10):979-90.

PubMed ID: 
18774912

Effect of gene therapy on visual function in Leber's congenital amaurosis

Bainbridge JW, Smith AJ, Barker SS, Robbie S, Henderson R, Balaggan K, Viswanathan A, Holder GE, Stockman A, Tyler N, Petersen-Jones S, Bhattacharya SS, Thrasher AJ, Fitzke FW, Carter BJ, Rubin GS, Moore AT, Ali RR. Effect of gene therapy on visual function in Leber's congenital amaurosis. N Engl J Med. 2008 May 22;358(21):2231-9.

PubMed ID: 
18441371

Leber congenital amaurosis

Perrault I, Rozet JM, Gerber S, Ghazi I, Leowski C, Ducroq D, Souied E, Dufier JL, Munnich A, Kaplan J. Leber congenital amaurosis. Mol Genet Metab. 1999 Oct;68(2):200-8. Review.

PubMed ID: 
10527670

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