corneal dystrophy

Tyrosinemia, Type II

Clinical Characteristics
Ocular Features: 

Keratitis is the outstanding ocular manifestation but not all patients have corneal involvement.  Symptoms include photophobia, pain, tearing, and redness which may occur as early as one year of age.  Corneal neovascularization, ulceration and scarring may lead to decreased visual acuity.  Linear and star-like corneal opacities in the epithelium resembling dendrites (pseudodendritic keratitis) have been described together with thickening of the conjunctiva.  The corneal lesions do not stain.  The conjunctival epithelium, fibrocytes, and blood vessel endothelial cells contain an accumulation of large inclusion bodies and tyrosine crystal-like structures. 

Systemic Features: 

Hydroxyphenylpyruvic acid is elevated in the urine and serum tyrosine levels are increased as the result of a defect in tyrosine aminotransferase.  Some patients have severe mental and somatic retardation.  The palms and soles can have painful punctate keratosis which may extend to the digits.  Developmental milestones such as walking are often delayed.  The keratotic lesions may be up to 2 cm in size. 

Genetics

Tyrosinemia type II is an autosomal recessive disorder caused by mutations in the tyrosine aminotransferase (TAT) gene at 16q22.1-q22.3. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

The hyperkeratosis and corneal opacities may improve with a diet low in phenylalanine and tyrosine but can recur after liberalization of the diet.  Benefits, if any, on CNS symptoms are unknown. 

References
Article Title: 

Mutation update, eleven novel mutations and description of five independent subjects with a novel founder mutation

Pena-Quintana L, Scherer G, Curbelo-Estevez ML, Jimenez-Acosta F, Hartmann B, Roche F, Meavilla-Olivas S, Perez-Cerda C, Garcia Segarra N, Giguere Y, Huppke P, Mitchell GA, Monch E, Trump D, Vianey-Saban C, Trimble ER, Vitoria-Minana I, Reyes-Suarez D, Ramirez-Lorenzo T, Tugores A. TYROSINEMIA TYPE II: Mutation update, eleven novel mutations and description of five independent subjects with a novel founder mutation. Clin Genet. 2017 Mar 3. doi: 10.1111/cge.13003. [Epub ahead of print].

PubMed ID: 
28255985

Sjogren-Larsson Syndrome

Clinical Characteristics
Ocular Features: 

The retina often has glistening white intraretinal dots which may be concentrated in the macula.  They have been found in 1 to 2 year old infants.  The macula may have ‘punched out’ lesions.  A pigmentary retinopathy is present in about 50% of patients and fluorescein angiography reveals a mottled hyperfluorescence. The cornea often has grayish stromal opacities that become vascularized, most commonly in the lower half.  Most patients have punctate keratitis resulting in marked photophobia.  Visual acuities can range from about 20/40 to finger counting.  The retinal changes may be progressive but EOG and ERG studies do not reveal abnormalities of retinal function.  VEPs though are often abnormal.  Ichthyosis may involve the lids and periorbital areas.

Systemic Features: 

The skin changes are present at birth and consist of an ichthyosiform erythroderma.  Hyperkeratosis is also present at birth and full blown ichthyosis develops during infancy.  The skin changes are most marked about the neck, flexion creases, and lower abdomen.  Scales in these areas are often darker than the surrounding skin.  Mental retardation may be mild to severe and spastic diplegia or quadriplegia is common but there is little evidence of progression.  There does not seem to be any correlation of age with the severity of neurological disease.

Genetics

Mutations in the ALDH3A2 gene (17p11.2) are responsible for this autosomal recessive disorder resulting in a deficiency of fatty aldehyde dehydrogenase. This can lead to long-chain fatty alcohol accumulation as demonstrated in the brain with proton magnetic resonance spectroscopy.

A form of Sjogren-Larsson syndrome with more severe neurologic signs is caused by recessive mutations in ELOVL4 (6p14,1),  Mutations in the same gene have been identified in patients with autosomal dominant Stargardt disease 3 (600110).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for this disorder but moisturizing skin treatments can be beneficial.

References
Article Title: 

Bietti Crystalline Corneoretinal Dystrophy

Clinical Characteristics
Ocular Features: 

The retina contains refractile glistening intraretinal crystals at all levels and choroidal vessels are said to be sclerosed.  The RPE atrophies and often forms pigment clumps.  The yellow-white crystals may be seen in the peripheral cornea and in the limbus.  Symptoms of night blindness and early vision loss begin about the third decade.  Night blindness is progressive as is the narrowing of the visual fields but this is highly variable between patients.  The visual field may show paracentral scotomas at some stage.  Central acuity can be normal until late in the disease when it becomes markedly impaired. Legal blindness can occur by the 5th decade of life. 

The ERG may show lack of rod and cone responses late in the disease and color vision may be lost.  However, the ffERG and mfERGs show decreases in amplitude of scotopic and photopic responses in all patients, even younger ones.  The EOG becomes abnormal in late stages.  The degree of involvement may be asymmetrical.  Complex lipid inclusions can be seen histologically in choroidal, conjunctival and skin fibroblasts, as well as in keratocytes and lymphocytes.

Crystalline deposits have been detected mostly in the proximal portions of RPE cells adjacent to degenerated retinal  areas.  Most common are circular hyperrefractive structures in the outer nuclear layer adjacent to areas of degeneration.  Some patients have cystoid macular edema. Others in late stages have fundus changes that resemble choroideremia.

Systemic Features: 

No other organ disease has been reported.

Genetics

This is an autosomal recessive disorder caused by mutations in the CYP4V2 gene (4q35.1) involved in fatty acid metabolism.

A homozygous CYP4V2 mutation has also been reported in patients with a choroideremia-like clinical phenotype.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment beyond low vision aids is available.

References
Article Title: 

Bietti crystalline corneoretinal dystrophy is caused by mutations in the novel gene CYP4V2

Li A, Jiao X, Munier FL, Schorderet DF, Yao W, Iwata F, Hayakawa M, Kanai A, Shy Chen M, Alan Lewis R, Heckenlively J, Weleber RG, Traboulsi EI, Zhang Q, Xiao X, Kaiser-Kupfer M, Sergeev YV, Hejtmancik JF. Bietti crystalline corneoretinal dystrophy is caused by mutations in the novel gene CYP4V2. Am J Hum Genet. 2004 May;74(5):817-26. Epub 2004 Mar 23.

PubMed ID: 
15042513

Dermochondrocorneal Dystrophy

Clinical Characteristics
Ocular Features: 

A corneal dystrophy is part of this syndrome.  Patients develop confluent, drop-like subepithelial whitish-brown infiltrates of the central cornea with some anterior stromal involvement together with stellate anterior cortical cataracts.  The intervening stroma appears hazy.  The epithelial surface remains intact but may be irregular over the superficial stromal infiltrates. The corneal opacities follow the skin and hand deformities and may be accompanied by a vascularized pannus.  Diagnosis can usually be made in the first decade of life.  Visual acuity in young adults may be reduced to the 20/80 - 20/100 range.

Systemic Features: 

Xanthomatous nodules are primarily located on the pinnae, hands, elbows, and nose.  Most of the nodules are small and primarily of cosmetic significance.  They have also been reported in oral mucosa and gingival tissue.  Hyperplasia of the oral mucosa is common.  Deformities of the hands and feet are also seen.

Genetics

Both autosomal dominant and autosomal recessive modes of inheritance have been proposed but insufficient numbers of families have been reported to be conclusive.

Treatment
Treatment Options: 

Corneal grafts could be visually beneficial but the vascularized pannus increases the risk of rejection.  CO2 laser treatment can reduce the cutaneous chondromes.  Gingival lesions and hyperplasia of the oral mucosa may require surgical treatment.

References
Article Title: 

Corneal Dystrophy, Avellino Type

Clinical Characteristics
Ocular Features: 

There is little to support the designation of a corneal dystrophy as 'Avellino type' but it is included in this database because it is entrenched in the literature.  It has features of both lattice dystrophy, type I, and granular dystrophy type I, which might be expected since all of these result from mutations in the same gene, TGFBI on chromosome 5.  Not surprisingly, reported cases have clinical and histological features of both lattice and granular dystrophy and hence are labeled as having combined granular-lattice corneal dystrophy.  There is considerable variation of the nature and quantity of the stromal deposits both within and among families, a common characteristic of autosomal dominant disorders.  Even though clinical evidence may suggest primarily lattice or granular dystrophy, histological studies can reveal changes characteristic of both.

Early cases could be traced to the Avellino region of Italy from which the title was derived but more recent reports have described families from around the world.

Systemic Features: 

No systemic disease is associated with this disorder.

Genetics

Mutations in the TGFBI (5q31) have been found in this so-called combined dystrophy.   Autosomal dominant transmission is evident from familial cases.  Mutations in the same gene also cause Thiel-Behnke (602082), Reis-Bucklers (608470), granular (Groenouw) type I (121900), lattice type I (122200) and epithelial basement membrane dystrophy (121820).  The combined features of lattice and granular dystrophies in the same corneas resulting from mutations in the same gene calls into question the value of relying solely on clinical and histological evidence to classify disease.  Modern genotyping now enables greater accuracy in the nosology and already the Cornea Society has incorporated this information in its recent reclassification of these dystrophies (Cornea Society IC3D Corneal Dystrophies(c)). 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Penetrating keratoplasty can improve vision at least temporarily but deposits tend to recur.  LASIK has been reported to exacerbate the number and density of the opacities.  Patients treated with PRK may do better and can retain corneal clarity for a decade or more.

References
Article Title: 

Avellino corneal dystrophy after LASIK

Jun RM, Tchah H, Kim TI, Stulting RD, Jung SE, Seo KY, Lee DH, Kim EK. Avellino corneal dystrophy after LASIK. Ophthalmology. 2004 Mar;111(3):463-8.

PubMed ID: 
15019320

Corneal Dystrophy, Congenital Endothelial 1

Clinical Characteristics
Ocular Features: 

(OMIM has combined this disorder with PPCD1 (122000) based on genetic and clinical evidence.)

Early onset limbus-to-limbus corneal clouding is the outstanding feature.  Some asymmetry is often present.  Vision is minimally impaired if at all in many children but slow progression occurs and adults often become visually impaired.  Nystagmus does not develop.  Photophobia and tearing are common.  The corneal appearance can lead to the erroneous diagnosis of congenital glaucoma.  However, some infants actually do have congenital glaucoma as well leading some to suggest this may be a disorder of anterior chamber dysgenesis.  The edematous cornea may be of 2-3 times normal thickness.  It may appear generally hazy and sometimes has a diffuse ground glass appearance.  

The posterior surface often appears mottled and has been described as having a peau d'orange appearance.  The endothelium is attenuated or even absent histologically and abnormal, disorganized collagen fibrils have been found in a thickened Descemet layer by electron microscopy.  The remaining endothelial cells are often vacuolated and heaped in double layers, with some containing melanin granules.  Some atrophy and edema of the epithelium with partial loss of Bowman's can be seen histologically.

Systemic Features: 

No systemic abnormalities are found in this disorder.

Genetics

This is an autosomal dominant disorder that maps to a locus on chromosome 20 (20p11.2-q11.2).   The molecular defect seems to involve the promotor of OVOL2 (20p11.23).  It is of interest that the posterior polymorphous corneal dystrophy 1 (PPCD1, 122000) mutation has been mapped to the same pericentric region, and it has been suggested that the two conditions may be allelic. These are now combined into a single entity in OMIM. 

This disorder should not be confused with congenital endothelial dystrophy type 2, CHED2 (217700) which is autosomal recessive, has an earlier presentation, and maps to a different region of chromosome 20.  Harboyan syndrome (217400) has similar corneal features but maps to a different location on chromosome 20 and is associated with sensorineural deafness.

The nosology of the corneal dystrophies is still evolving.  In the 2015 edition of the IC3D, this condition designated CHED1 is eliminated based on clinical and pathologic similarities to those in posterior polymorphous corneal dystrophy 1 (PPCD1, 122000).  However, while the loci for PPCD2 and CHED1 are located in the same pericentric region of chromosome 20, the purported mutations occur in different genes. 

 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Penetrating keratoplasty carries a good visual prognosis, even when done late in life.

References
Article Title: 

IC3D classification of corneal dystrophies--edition 2

Weiss JS, Moller HU, Aldave AJ, Seitz B, Bredrup C, Kivela T, Munier FL, Rapuano CJ, Nischal KK, Kim EK, Sutphin J, Busin M, Labbe A, Kenyon KR, Kinoshita S, Lisch W. IC3D classification of corneal dystrophies--edition 2. Cornea. 2015 Feb;34(2):117-59. Erratum in: Cornea. 2015 Oct;34(10):e32.

PubMed ID: 
25564336

Corneal Dystrophy, Congenital Stromal

Clinical Characteristics
Ocular Features: 

This rare congenital form of stromal dystrophy is sometimes considered a disorder of collagen fibrils with abnormally small diameters.  These may appear disorganized in areas.  Corneal opacities are often evident at birth or during the neonatal period.  Numerous small spots of fluffy, flaky deposits are found throughout the stroma creating a diffuse cloudy appearance and these may become more numerous with age indicating some progression.  The epithelium, Descemet membrane and the endothelium are not affected and the stroma is of normal or slightly increased thickness.  In some areas abnormal fibrillar layers are seen.  Although corneal erosions and photophobia are usually not clinically significant, acuity may be as low as hand motions and penetrating keratoplasty may be indicated.  In one series this was necessary at an average age of 20 years.  In the same series of 11 patients, 4 had strabismus, 3 eyes developed open angle glaucoma and band keratopathy was present in one patient.  Nystagmus has not been reported.

Deposition of abnormal decorin contributes to the stromal opacities. 

Systemic Features: 

No systemic abnormalities have been reported.

Genetics

This is a rare autosomal dominant stromal dystrophy that results from a mutation in the DCN gene on chromosome 12 (12q21.3).  Several frameshift mutations have been reported    in the decorin (DCN) gene causing premature truncation of the protein product.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Penetrating keratoplasty can be successful in restoring vision.  Grafts have been reported to remain clear for up to 36 years in more than half of the patients in one series but opacities recurred in others.

References
Article Title: 

Corneal Dystrophy, Fleck

Clinical Characteristics
Ocular Features: 

This stromal dystrophy may be congenital as it can be seen in the first years of life.  It is nonprogressive and generally has little clinical significance as it does not impair vision or require treatment in most cases.  It is usually diagnosed on routine examination from the presence of multiple, minute, whitish or grayish discrete opacities throughout the stroma.  The largest numbers are located centrally and posteriorly.  These may be flat, round or oval, and sometimes resemble snowflakes.  Keratocyte cell bodies contain cytoplasmic inclusions or vacuoles likely as the result of defective intracellular organelle trafficking.  Other layers such as the epithelium, Bowman layer, Descemet and endothelium are normal.  Expressivity is highly variable with considerable asymmetry of opacities in the two eyes and even unilateral involvement.

Systemic Features: 

No systemic abnormalities have been reported.

Genetics

This is an autosomal dominant stromal dystrophy resulting from mutations in the PIKFYVE (PIP5K3) gene on chromosome 2 (2q35).  A variety of missense, frameshift, and protein-truncating mutations have been found.  The gene product is a member of the phosphoinositide 3-kinase family that regulates the synthesis, sorting, and transportation of intracellular multivesicular bodies.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is required in most cases.

References
Article Title: 

Corneal Dystrophy, Gelatinous Drop-like

Clinical Characteristics
Ocular Features: 

White, gelatinous deposits of amyloid are seen in the subepithelial region giving the surface of the cornea a multilobulated appearance resembling a mulberry.  These usually appear in the first decade of life and cause photophobia as well as tearing from irritation caused by a severe foreign body sensation.  The corneal changes are variable and some patients have only a mild amount of anterior stromal opacification while others have subepithelial vascularization.  Vision loss can be severe when the deposits coalesce to opacify the cornea.  These deposits are found in the subepithelial region but in some families it may also be found in the Bowman layer.   The appearance of fusiform deposits in the stroma in some patients has led some to categorize gelatinous drop-like corneal dystrophy as a lattice dystrophy and have designated it as type III.  GDLD seems to occur more commonly in Japan but often has a much later onset and the lattice appearance is more striking suggesting that it may be a unique form of corneal amyloidosis.  True GDLD, however, occurs in diverse ethnic groups throughout the US, Europe, Latin America, and the Asian subcontinent.  Cataracts have been reported in several young individuals with corneal amyloidosis.

Systemic Features: 

No systemic abnormalities occur as part of this syndrome.

Genetics

Autosomal recessive corneal amyloidosis results from multiple mutations in the M1S1 (TACSTD2) gene located on chromosome 1 (1p32).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No satisfactory permanent treatment has been found.  Ablative treatments may give temporary relief from symptoms and improve vision but the deposits recur within a few years.

References
Article Title: 

Corneal Dystrophy, Fuchs Endothelial, Late Onset

Clinical Characteristics
Ocular Features: 

There are a number of endothelial corneal dystrophies to which Fuchs name has been attached, including two that are early in onset, or even congenital (CHED1; 121700), (CHED2; 217700) and at least three that have an adult onset, one (Fuchs endothelial dystrophy, early onset; 136800) which has a relatively early onset and two considered to have a late onset: the one described here and another known as Fuchs Endothelial Dystropy, Late Onset 2 (613267).  Evidence for multiple distinct types comes from genotyping which reveals considerable genetic heterogeneity in spite of similar phenotypes (see Genetics).  All are progressive and degenerative with various degrees of visual disability.  Most have histologic changes in both the endothelial cells and Descemet membrane.

The entity described here likely is the classical disease described in the older literature.  It is certainly the most common, occurring in 4% of the population over the age of 40 years and for unknown reasons is more often found in females.  Guttae are formed as excrescences of Descemet's membrane and develop initially in the central cornea, beginning about the 5th decade, gradually increasing in number and size toward the periphery. They tend to be relatively large, sharply peaked and often positioned at the cell-cell junctions of endothelial cells.  These are often best visualized by corneal transillumination.  Histologically, the posterior portion of Descemet membrane contains bundles and sheets of abnormal collagen.  Progressive corneal edema follows as endothelial cells are lost and the remaining ones are unable to maintain normal stromal hydration.  Fingerprint lines may be present.  The corneal edema may involve both stroma and epithelium and in advanced stages may lead to painful epithelial erosions.  The disease is relentless and early blurring of vision progresses to significant visual handicaps often requiring corneal transplantation in the 7th and 8th decades.

Corneal guttae are common in older individuals but usually are located more peripherally.  The diagnosis of Fuchs can best be made where the guttae are concentrated centrally and associated with stromal and epithelial edema.

Systemic Features: 

No systemic abnormalities have been reported.

Genetics

Late onset Fuchs of this type is due to a mutation on chromosome 13 (13pter-q12.13) but the specific molecular basis for the disease remains unclear.  Many cases occur sporadically but some pedigrees are consistent with autosomal dominant inheritance.  For unknown reasons females are more commonly affected and often have more severe disease.  Recent reports suggest that missense mutations in ZEB1 may be responsible for at least some cases of late-onset Fuchs.  This mutation has also been found in cases of type 3 posterior polymorphous dystrophy (609141) suggesting that the two conditions may be allelic.

Other rare forms of late onset endothelial dystrophy to which the eponymic designation of Fuchs has been applied include FECD3 (613267) in which various mutations in the TCF4 locus on chromosome 18 (18q21.2-q21.3) (and expanded TGC trinucleotide repeats) have been implicated.  Other variants of Fuchs endothelial dystrophy include FECD4 (613268) with a mutation in SLC4A11 (20p13-p12), FECD5 (613269) with a possible mutation on chromosome 5 (5q33.1-q35.2), FECD6 (613270) due to a mutation in ZEB1 on chromosome 10 (10p11.2), and FECD7 (613271) that can be mapped to chromosome 9 (9p24.1-p22.1).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Corneal transplantation has a good prognosis and posterior lamellar grafting may be the technique of choice.  In some patients, visually significant cataracts are present before the cornea is severely involved and a triple procedure may be considered.  However, this is best determined by pachymetry.  Individuals with a preoperative corneal thickness of even >600 micrometers can do well after cataract surgery for a number of years before the cornea needs to be replaced.

References
Article Title: 

E2-2 protein and Fuchs's corneal dystrophy

Baratz KH, Tosakulwong N, Ryu E, Brown WL, Branham K, Chen W, Tran KD, Schmid-Kubista KE, Heckenlively JR, Swaroop A, Abecasis G, Bailey KR, Edwards AO. E2-2 protein and Fuchs's corneal dystrophy. N Engl J Med. 2010 Sep 9;363(11):1016-24.

PubMed ID: 
20825314

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