X-linked recessive

Microphthalmia, Syndromic 1

Clinical Characteristics
Ocular Features: 

Microphthalmia is often a part of other ocular and systemic anomalies.  The full range of essential features of Lenz microphthalmia remains unknown but is often diagnosed in males when colobomas and microcornea are associated with mental deficits together with urogenital and skeletal anomalies.  Microphthalmos may be unilateral and ocular cysts are common.  The globes may be sufficiently small that anophthalmia is sometimes diagnosed but this is a misnomer as some ocular tissue is always present.   Sixty per cent of eyes have colobomas which are often bilateral and may involve the optic disc, choroid, ciliary body, and iris.  Blindness is common.  

Systemic Features: 

A large number of associated systemic anomalies have been reported with this type of microphthalmia.  Skeletal features include microcephaly, spinal deformities, high arched palate, pectus excavatum, absent or dysplastic clavicles (accounting for the narrow or sagging shoulders), and digital anomalies including syndactyly, duplicated thumbs and clinodactyly.  Physical growth retardation is evident by shortness of stature.   Urogenital malformations are present in 77% of individuals and include hypospadius, cryptorchidism, hydroureter, and renal dysgenesis.  Dental anomalies include oligodontia and irregular lower incisors that may be widely spaced.  Some degree of intellectual disability is present in 63%.  The ears may be abnormally shaped, low-set, rotated posteriorly, and anteverted. 

Genetics

This is a rare X-linked disorder that is apparently due to an unknown mutation at Xq27-Xq28.  No male-to-male transmission has been observed but affected males rarely reproduce as a result of various urogenital anomalies.

A somewhat similar X-linked syndrome of microphthalmia, sometimes called OFCD syndrome (syndromic 2 microphthalmia; 300166) has been reported to be caused by mutations in BCOR (Xp11.4).  This MCOPS2 disorder is often considered to be X-linked dominant with lethality in males.

Another X-linked non-syndromic form of microphthalmia with colobomas has been reported (Microphthalmia with Coloboma, X-Linked; 300345).  In addition there is a similar disorder of simple Microphthalmia with Coloboma that is inherited either in an autosomal dominant or autosomal recessive pattern (605738, 610092, 611638, 613703, 251505 ).

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

There is no treatment beyond supportive care for specific health issues. 

References
Article Title: 

Cataracts, Congenital, X-Linked

Clinical Characteristics
Ocular Features: 

The unique status of this type of X-linked cataract is uncertain as the phenotype is highly variable.  It is listed separately in this database because some patients do not have the dysmorphic features of Nance-Horan syndrome (302350) which also is caused by mutations in the NHS gene.  Lens opacities in males usually occur in the nucleus which may cause severe visual impairment.  Heterozygous females have granular opacities along the Y sutures but these may also be seen in males.  Microcornea, variable microphthalmia, and congenital glaucoma (usually secondary) have been noted in a few patients.  

Systemic Features: 

Facial dysmorphology, intellectual impairment, and dental anomalies are often found in patients with X-linked cataracts as part of the Nance-Horan syndrome (302350).  However, these signs may not always be apparent and therefore were not reported in early publications which adds uncertainty to the classification.  That said it is also true that some families in which X-linked cataracts segregate do not have the systemic features in spite of detailed examinations even though they have mutations in NHS. 

Genetics

A mutation in the NHS gene (Xp22.13) can be responsible for X-linked cataracts.   Mutations in the same gene cause Nance-Horan syndrome (302350).  Individuals with typical X-linked cataracts, however, may or may not have systemic malformations. 

A variety of alterations in the NHS gene, including copy number variations, intragenic deletions, and duplication/triplication arrangements, have been found and are likely responsible for the clinical heterogeneity and current nosological confusion.  Until additional fine genotyping is available for more patients it is not possible to determine if a category of X-linked cataracts without NHS mutations exists. 

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

Visually significant cataracts must be removed early to allow normal visual development.  Secondary glaucoma and retinal detachments are post-operative risks. 

References
Article Title: 

X-linked cataract and Nance-Horan syndrome are allelic disorders

Coccia M, Brooks SP, Webb TR, Christodoulou K, Wozniak IO, Murday V, Balicki M, Yee HA, Wangensteen T, Riise R, Saggar AK, Park SM, Kanuga N, Francis PJ, Maher ER, Moore AT, Russell-Eggitt IM, Hardcastle AJ. X-linked cataract and Nance-Horan syndrome are allelic disorders. Hum Mol Genet. 2009 Jul 15;18(14):2643-55.

PubMed ID: 
19414485

Nance-Horan Syndrome

Clinical Characteristics
Ocular Features: 

Congenital cataracts are a feature of this X-linked disorder.  These consist of bilateral, dense nuclear opacification (in most males) but sutural opacities are also seen, especially in carrier females.  If the nuclear cataracts are not treated promptly, severe amblyopia, nystagmus, and strabismus may result.  Microcornea, congenital glaucoma, scleral staphylomas, and retinal cystoid degeneration may also be present.  Microphthalmia has been described. These ocular signs are present in 90% of heterozygous females but they may be subtle and careful examination is required to identify them.  Cataract surgery is usually not required in females. 

Systemic Features: 

This is a developmental disorder in which facial dysmorphism and dental anomalies are consistent systemic features in affected males.  Some patients (30%) also have some intellectual impairment while others have developmental delays and behavior problems.  The pinnae may be anteverted and often appear large while the nose and nasal bridge are prominent.  The teeth in males are small and pointed or 'screwdriver shaped' and are widely separated (sometimes called Hutchinson teeth).  The enamel may be hypoplastic and dental agenesis can be present.  Supernumerary incisors have been described.  The facial and dental features may be present in female carriers but are less pronounced.  Females do not have intellectual impairment. 

Genetics

This is an X-linked recessive (dominant?) disorder resulting from mutations in the NHS gene located at Xp22.13.  However, heterozygous females may have clinical manifestations, including dense cataracts, and all offspring of such females need ophthalmological evaluations at birth.

It is likely that at least some cases of X-linked congenital cataract (CXN; 302200) represent this disorder because the facial dysmorphism may be subtle and easily missed in Nance-Horan.  Of course, the two disorders may also be allelic.  A variety of alterations in the NHS gene, including copy number variations, intragenic deletions, and duplication/triplication arrangements, have been found.  The occasionally subtle facial dysmorphology and the dental abnormalities are easily missed in patients in whom congenital cataracts are the primary clinical concern.  

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

Visually significant cataracts should be removed early to allow for normal visual maturation.  Glaucoma must be treated appropriately.  At risk males and females should have dental X-rays and dental surgery may be required.  Special education may be beneficial in males. 

References
Article Title: 

X-linked cataract and Nance-Horan syndrome are allelic disorders

Coccia M, Brooks SP, Webb TR, Christodoulou K, Wozniak IO, Murday V, Balicki M, Yee HA, Wangensteen T, Riise R, Saggar AK, Park SM, Kanuga N, Francis PJ, Maher ER, Moore AT, Russell-Eggitt IM, Hardcastle AJ. X-linked cataract and Nance-Horan syndrome are allelic disorders. Hum Mol Genet. 2009 Jul 15;18(14):2643-55.

PubMed ID: 
19414485

Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation

Burdon KP, McKay JD, Sale MM, Russell-Eggitt IM, Mackey DA, Wirth MG, Elder JE, Nicoll A, Clarke MP, FitzGerald LM, Stankovich JM, Shaw MA, Sharma S, Gajovic S, Gruss P, Ross S, Thomas P, Voss AK, Thomas T, Gecz J, Craig JE. Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation. Am J Hum Genet. 2003 Nov;73(5):1120-30.

PubMed ID: 
14564667

Adrenoleukodystrophy, X-Linked

Clinical Characteristics
Ocular Features: 

Virtually all patients have visual symptoms.  Loss of acuity, hemianopia, visual agnosia, optic atrophy, and strabismus are the most common features.   Neuropathy may cause a decrease in corneal sensation.  Gaze abnormalities due to ocular apraxia are sometimes seen.  Ocular symptoms often occur after the systemic abnormalities are noted.  However, there is considerable heterogeneity in age of onset and progression of symptoms.

Histopathology of ocular structures reveals characteristic inclusions in retinal neurons, optic nerve macrophages, and the loss of ganglion cells with thinning of the nerve fiber layer of the retina. 

Systemic Features: 

This is a peroxisomal disorder of very-long-chain fatty acid (VLCF) metabolism that leads to progressive neurological and adrenal dysfunction from accumulation of VLCFAs in the nervous system, adrenal glands, and testes.  The age of onset and clinical course are highly variable and there may be several forms.  The childhood form begins between the ages of 4 and 8 years but in other patients with the adult form, symptoms may not appear until the third decade of life.  A viral illness may precipitate the onset.   Symptoms of both central and peripheral neurologic disease are often present with cognitive problems, ataxia, spasticity, aphasia, and loss of fine motor control.  Hearing loss is seen in some patients.  Younger patients tend to have more behavioral problems while older individuals may develop dementia.

Adrenal insufficiency leads to skin hyperpigmentation, weakness, loss of muscle mass and eventually coma.  Impotence in males is common. 

Genetics

This is an X-linked disorder secondary to mutations in the ABCD1 gene (Xp28).  The result is a deficiency in the cellular transporter known as adrenoleukodystrophy protein that is active in perioxosomes.

Although this X-linked disorder is primarily manifest in males, between 20 and 50% of female carriers have at least some symptoms, usually with a later onset than seen in males.

There are also rare cases with an apparent autosomal recessive pattern of inheritance (NALD) (202370) having an earlier onset and more aggressive course. 

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

Treatment of adrenal insufficiency is important and can be lifesaving.  Low vision aids, physical therapy and special education may be helpful.  Some young patients with early disease have benefitted from bone marrow transplantation.  "Lorenzo's Oil" (a mixture of oleic acid and erucic acid) has been reported to reduce or delay symptoms in some boys.

Recent reports suggest new treatment modalities may hold promise.  Infusion of autologous CD34+ cells transduced with the Lentin-D lentiviral vector reduced major symptoms in 15 of 17 boys within 29 months after treatment.  Likewise, intrathecal baclofen treatment in two boys with rapidly advancing cerebral manifestations provided symptomatic and palliative improvement.

 

References
Article Title: 

Hematopoietic Stem-Cell Gene Therapy for Cerebral Adrenoleukodystrophy

Eichler F, Duncan C, Musolino PL, Orchard PJ, De Oliveira S, Thrasher AJ, Armant M, Dansereau C, Lund TC, Miller WP, Raymond GV, Sankar R, Shah AJ, Sevin C, Gaspar HB, Gissen P, Amartino H, Bratkovic D, Smith NJC, Paker AM, Shamir E, O'Meara T, Davidson D, Aubourg P, Williams DA. Hematopoietic Stem-Cell Gene Therapy for Cerebral Adrenoleukodystrophy. N Engl J Med. 2017 Oct 4. doi: 10.1056/NEJMoa1700554. [Epub ahead of print].

PubMed ID: 
28976817

X-linked adrenoleukodystrophy

Moser HW, Mahmood A, Raymond GV. X-linked adrenoleukodystrophy. Nat Clin Pract Neurol. 2007 Mar;3(3):140-51. Review.

PubMed ID: 
17342190

Color Blindness, Red-Green, Partial

Clinical Characteristics
Ocular Features: 

Human color vision is trichromatic and requires the normal function of three classes of cones responding to wavelengths of approximately 420nm (blue cones), 530 nm (green cones), and 560 nm (red cones).  Dichromatic color vision discussed here is based on responses of red and green cones whose pigments are generated from contiguous gene regions on the X chromosome encoding OPN1MW (green pigment), and OPN1LW (red pigment).

The degree of color deficiency is variable and some males are so mildly affected that they are unaware of any defect until tested.  The human eye is capable of seeing about a million colors which is made possible in part by the wide range of comparative signal outputs from the three classes of cones.  In addition, the ratio of red and green cones varies among individuals and these factors collectively influence how each individual interprets the spectrum of wavelengths that enter the eye.  The phenotype of red-green color blindness is highly variable.  

Four subclasses of red-green color vision defects are recognized:

               Protanopia - only blue and green cones are functional (1 percent of Caucasian males) 

               Deuteranopia - only blue and red cones are functional (1 percent of Caucasian males)

               Protanomaly - blue and some green cones are normal plus some anomalous green-like cones (1  percent of Caucasian males)

               Deuteranomaly - normal blue and some red cones are normal plus some anomalous red-like cones (5 percent of Caucasian males)

Blue color blindness (tritanopia; 190900) is the result of mutations in the OPN1SW gene on chromosome 7. ERG flicker responses can be used to define the type and nature of the cone defects. 

Systemic Features: 

There are no systemic abnormalities. 

Genetics

Red-green color perception is based on gene products called opsins which, combined with their chromophores, respond to photons of specific wavelengths.  The OPN1LW and OPN1MW genes reside in a cluster with a head-to-tail configuration on the X chromosome at Xq28.  Red-green color vision defects are therefore inherited in an X-linked recessive pattern.  There is a single gene for the red cone opsin but there are multiple ones for the green pigment.  Only the red gene and the immediately adjacent green pigment gene are expressed.  All are under the control of a master switch called the locus control region, LCR.

These DNA segments undergo relatively frequent unequal crossovers which can disrupt the color sensitivity of the gene products so that red-green colorblindness in some form is the most common type of anomalous color vision.  It is found in approximately 8% of males and perhaps 0.5% of females. 

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

No treatment is available for red-green color blindness although appropriately tinted lenses may enhance the perception of certain shades for specific tasks. 

Early work in non-human primates suggest that viral-mediated gene therapy can restore trichromacy to at least some extent.

References
Article Title: 

Microphthalmia with Coloboma, X-Linked

Clinical Characteristics
Ocular Features: 

Isolated colobomatous microphthalmia is caused multiple mutations and usually inherited in an autosomal dominant pattern.  Type 1 is an X-linked disorder with typical features of small eyes, small corneas, colobomas, and elevated intraocular pressures. 

Systemic Features: 

By definition no systemic disease is present. 

Genetics

The combination of colobomas and microphthalmia is found in numerous heritable syndromes but also occurs in isolation.  X-linked syndromes with this combination usually include mental retardation and cataracts but these are absent in the isolated type described here.  A locus on the X chromosome was identified to lie either on the proximal short arm or the proximal long arm but no specific mutation or gene has been identified.  In the single multigenerational reported family, all affected individuals were male except for one female in whom non-random X-inactivation was postulated. 

Syndromal forms of X-linked microphthalmia with coloboma (309800 ) have also been reported.

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

No treatment is available for the malformations but low vision aids should be considered for appropriate individuals. 

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: 

Cone-Rod Dystrophies, X-Linked

Clinical Characteristics
Ocular Features: 

Three X-linked forms of progressive cone-rod dystrophies each with mutations in different genes have been identified.  Central vision is often lost in the second or third decades of life but photophobia is usually noted before vision loss.  Cones are primarily involved but rod degeneration occurs over time.  The ERG reveals defective photopic responses early followed by a decrease in rod responses.   All three types are rare disorders affecting primarily males with symptoms of decreased acuity, photophobia, loss of color vision, and myopia.  The color vision defect early is incomplete but progressive cone degeneration eventually leads to achromatopsia.    Peripheral visual fields are usually full until late in the disease when constriction and nightblindness are evident.  The retina may have a tapetal-like sheen.  RPE changes in the macula often give it a granular appearance and there may be a bull's-eye configuration.   Fine nystagmus may be present as well.  The optic nerve often has some pallor beginning temporally.  Carrier females can have some diminished acuity, myopia, RPE changes, and even photophobia but normal color vision and ERG responses at least among younger individuals.

There is considerable variation in the clinical signs and symptoms in the X-linked cone-rod dystrophies among both affected males and heterozygous females.  Visual acuity varies widely and is to some extent age dependent.  Vision can be normal into the fourth and fifth decades but may reach the count fingers level after that. 

Systemic Features: 

None.

Genetics

Mutations in at least 3 genes on the X chromosome cause X-linked cone-rod dystrophy.

CORDX1 (304020) is caused by mutations in an alternative exon 15 (ORG15) of the RPGR gene (Xp11.4) which is also mutant in several forms of X-linked retinitis pigmentosa (300455, 300029).  These disorders are sometimes considered examples of X-linked ocular disease resulting from a primary ciliary dyskinesia (244400).

CORDX2 (300085) is caused by mutations in an unidentified gene at Xq27.  A single family has been reported.

CORDX3 (300476) results from mutations in CACNA1F.  Mutations in the same gene also cause a form of congenital stationary night blindness, CSNB2A (300071).  The latter, however, is a stationary disorder with significant nightblindness and mild dyschromatopsia, often with an adult onset, and is associated with high myopia. Aland Island Eye Disease (300600) is another allelic disorder.   

Pedigree: 
X-linked dominant, father affected
X-linked dominant, mother affected
X-linked recessive, carrier mother
X-linked recessive, father affected
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: 

Blue Cone Monochromacy

Clinical Characteristics
Ocular Features: 

This is usually a stationary cone dysfunction disorder in which the causative mechanism has yet to be worked out.  Typical patients have severe visual impairment from birth and some have pendular nystagmus and photophobia similar to other achromatopsia disorders.  Vision seems to be dependent solely on blue cones and rod photoreceptors.  The ERG always shows relatively normal rod function whereas the cones are usually dysfunctional. 

In some families, however, there is evidence of disease progression with macular RPE changes and myopia.  This has led to the designation of 'cone dystrophy 5' for such cases even though the mutation locus impacts the same cone opsin genes at Xq28 that are implicated in the more typical BCM phenotype.

Systemic Features: 

None.

Genetics

This is an X-linked recessive form of colorblindness in which DNA changes in the vicinity of Xq28 alters the red and green visual pigment cluster genes via recombination or point mutations.  Alternatively, the control locus adjacent to the cluster may be altered.  In either case, the result may be a loss of function of these genes leaving blue-cone monochromacy.

The mutation for cone dystrophy 5 maps to Xq26.1-qter but the locus encompasses the opsin gene complex at Xq28 as well. 

At least a quarter of individuals with blue cone monochromacy, however, do not have mutations in the vicinity of Xq28 suggesting that additional genetic heterogeneity remains.

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

Low vision aids can be helpful.  Tinted lenses for photophobia allow for greater visual comfort.  A magenta (mixture of red and blue) tint allows for best visual acuity since it protects the rods from saturation while allowing the blue cones to be maximally stimulated. 

References
Article Title: 

X-linked cone dystrophy caused by mutation of the red and green cone opsins

Gardner JC, Webb TR, Kanuga N, Robson AG, Holder GE, Stockman A, Ripamonti C, Ebenezer ND, Ogun O, Devery S, Wright GA, Maher ER, Cheetham ME, Moore AT, Michaelides M, Hardcastle AJ. X-linked cone dystrophy caused by mutation of the red and green cone opsins. Am J Hum Genet. 2010 Jul 9;87(1):26-39.

PubMed ID: 
20579627

Genetic heterogeneity among blue-cone monochromats

Nathans J, Maumenee IH, Zrenner E, Sadowski B, Sharpe LT, Lewis RA, Hansen E, Rosenberg T, Schwartz M, Heckenlively JR, et al. Genetic heterogeneity among blue-cone monochromats. Am J Hum Genet. 1993 Nov;53(5):987-1000.

PubMed ID: 
8213841

Molecular genetics of human blue cone monochromacy

Nathans J, Davenport CM, Maumenee IH, Lewis RA, Hejtmancik JF, Litt M, Lovrien E, Weleber R, Bachynski B, Zwas F, et al. Molecular genetics of human blue cone monochromacy. Science. 1989 Aug 25;245(4920):831-8.

PubMed ID: 
2788922

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

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