lattice degeneration

Glaucoma, Pigment Dispersion Syndrome

Clinical Characteristics
Ocular Features: 

This is a form of open angle glaucoma with early onset (usually before the age of 40 years).  Marked pigment deposition in the trabecular meshwork, on the lens, zonules, and the corneal endothelium can often be seen prior to elevation of the intraocular pressure. It can be present asymmetrically, even unilaterally, but primarily in early stages.  The pigment source in humans seems to be the iris in which hypopigmentation leads to radial transillumination defects and mouse models corroborate this.  The iris configuration is sometimes described as flat or even concave.  The pattern of pigment deposition on the posterior surface of the cornea is known as a Krukenberg spindle and considered diagnostic.  Untreated, the characteristic optic nerve damage and visual field changes of glaucoma eventually occur.  Early-onset and rapidly progressive nuclear cataracts have been reported in some patients.

In one longitudinal study of 113 patients diagnosed with pigment dispersion and followed for 24 years, 23 had glaucoma initially and 9 more eventually required treatment for elevated pressure. The mean age at diagnosis was 42 years and myopic males were the most commonly affected.

The syndromic nature of PDS is suggested by the association of lattice degeneration, retinal tears, and detachments in a significant number of individuals.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal dominant form of glaucoma-related optic neuropathy that shares some features with open angle juvenile glaucoma (137750), such as myopia and early onset.  The pigment dispersion syndrome described here, however, maps to a different locus (7q35-q36).  Another candidate locus is located at 18q11-q21 but the causative mutations remain elusive.

A four generation family with an apparent autosomal recessive pattern has been reported.

The autosomal dominant pattern is not always apparent from history alone and examination of relatives is necessary to document the familial nature of this disease. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The usual glaucoma therapies are indicated.  Some have advised limiting vigorous impact sports to reduce the amount of pigment released.  All individuals with pigment dispersion must be followed vigilantly for development of glaucoma as the risk is high.  It has been estimated to be 10% within 5 years and 15% in 15 years, regardless of age and family history.  Further, the pigment dispersion is progressive along with the risk of elevated pressure as eventually 30 -50% of patients develop glaucoma.  However, regression of pigment deposition, decrease of iris transillumination and even stabilization of pressure has also been noted in some, mostly younger, patients.

Laser iridotomy has been suggested as therapeutically useful in the reduction of the IOP but there is no statistical confirmation of this.

References
Article Title: 

Spondyloepiphyseal Dysplasia Congenita

Clinical Characteristics
Ocular Features: 

Patients characteristically have vitreous abnormalities described as veils or stands.  The central vitreous may undergo liquefaction and the peripheral vitreous sometimes creates traction on the retina.  High myopia with progression is common and a significant proportion of patients suffer detachments of the retina even in the absence of myopia.  Lattice degeneration is frequently seen.  Most patients have 20/50 or better vision.

Systemic Features: 

Dwarfism with kyphosis and a barrel chest are characteristic.  The vertebrae are often flattened and malformed and the neck is short.  Delayed ossification in the epiphyses and the os pubis is common.  The disorder can be evident at birth but the full syndrome may not be evident until 3 or 4 years of age.  Radiologic studies are important in making the diagnosis.

Genetics

This is generally considered an autosomal dominant disorder secondary to mutations in the COL2A1 gene impacting type II collagen.  This type of collagen is found primarily in cartilage and vitreous and a number of type II collagenopathy disorders are associated with vitreoretinopathy and joint disease of which Stickler syndrome type I (609508, 108300) is the most common.  Other disorders in this database caused by mutations in COL2A1 are: Kniest dysplasia (156550), Stickler syndromes type I (609508, 108300 ) and II (604841), vitreoretinopathy with epiphyseal dysplasia (120140), and spondyloepiphyseal dysplasia congenita (183900).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Cervical fusion is sometimes used when odontoid hypoplasia leads to hypermobility of the cervical vertebrae.  Retinal detachments, of course, need to be repaired.

References
Article Title: 

Retinal Detachment with Lattice Degeneration

Clinical Characteristics
Ocular Features: 

Lattice degeneration of the retina is well known to increase the risk of retinal detachment.  Lattice is found in 40% of all rhegmatogenous retinal detachments but is present in only 7-10% of eye bank eyes.  Lattice degeneration by itself can lead to retinal detachment in less than 1% of patients but the risk increases into the 50% range when myopia is also present. 

A four generation pedigree of 88 individuals has been reported in which 22% had lattice without myopia and 6% developed retinal detachments.  The atrophic changes were progressive since among those of the most recent generation, 9.5% had lattice at an average of 11 years whereas 75% in earlier generations had such changes at an average age of 56 years.

Systemic Features: 

No systemic abnormalities have been reported in this disorder.

Genetics

The reported pedigree showed a clear autosomal dominant pattern with male-to-male transmission.

Rhegmatogenous retinal detachments without lattice have also been reported in autosomal dominant patterns but at least some are due to mutations in COL2A1.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Repair of the retinal detachment is indicated. No information regarding the benefits of prophylactic treatment is available. It may be prudent to counsel patients with this mutation to avoid contact sports and blunt trauma.

References
Article Title: 

Stickler Syndrome, Type I

Clinical Characteristics
Ocular Features: 

High myopia and vitreous degeneration dominate the ocular manifestations of Stickler syndrome, type I.  The vitreous often appears optically empty as it liquefies and the fibrils degenerate.  The vitreous is sometimes seen to form 'veils', especially in the retrolenticular region but they may also float throughout the posterior chamber.  They are often attached to areas of lattice degeneration in the retina as well as other areas.  Posterior vitreous detachments are common.  Vitreoretinal degeneration is progressive and by the second decade rhegmatogenous detachments occur in half of affected patients.  As many as three quarters of adult patients have retinal breaks.  The retina has pigmentary changes with deposition circumferentially near the equator and more peripherally.  Hypopigmentation is more common early creating a tessellated appearance.  Lenticular opacities occur also early with cortical flecks and wedge-shaped changes.

The ERG may be normal early but evidence of rod and cone dysfunction soon appears and is progressive.  Dark adaptation is defective later in the course of the disease.  The EOG is virtually always depressed.  The visual field is constricted and may show a ring scotoma coincident with the equatorial chorioretinal atrophy.

Glaucoma is not uncommon and may be infantile in onset and difficult to control.  

Phthisis is a significant risk especially for individuals who have multiple surgical procedures for retinal detachments. 

Systemic Features: 

It has been suggested that there is a nonsyndromic or ocular type of Stickler syndrome lacking many of the extraocular features characteristic of the complete syndrome.  However, the evidence for the ocular type described here as a distinct entity remains slim and the clinical picture may simply reflect variable expressivity of mutations in the same gene.  Type I Stickler syndrome has multiple systemic features such as cleft palate, hearing impairment, premature arthritis, micrognathia, kyphoscoliosis, and some signs such as arachnodactyly that are found in the Marfan syndrome.

Genetics

This is an autosomal dominant disease of collagen formation as a result of mutations in the COL2A1 gene (12q13.11-q13.2). The mutations causing both syndromal and the suggested nonsyndromal ocular type of Stickler disease are in the same gene.  Mutations in the same gene are known to cause autosomal dominant rhegmatogenous retinal detachments in patients who have none of the systemic clinical signs (609508).  These patients may lack the signs of vitreous degeneration seen in Kniest dysplasia (156550)  and in the disorder described here.

There is better evidence for a second type of Stickler syndrome, STL2 or type II (604841) based on phenotypic differences and the fact that a second locus (1p21) containing mutations in COL11A1 has been linked to it. 

Type III is caused by mutations in COL11A2 and has systemic features similar to types I and II but lacks the eye findings since this gene is not expressed in the eye.

Type IV also has important ocular features but is an autosomal recessive disorder caused by mutations in COL9A2.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The combination of progressive vitreoretinal degeneration, frequency of posterior vitreous detachments, and axial myopia creates a lifelong threat of retinal tears and detachments.   Half to three quarters of all patients develop retinal tears and detachments.  Certainly all patients with Stickler syndrome deserve repeated and thorough retinal exams throughout their lives.  In addition to prompt treatment of tears and detachments, some have advocated prophylactic scleral banding to reduce vitreous traction, or applying 360 degree cryotherapy.

References
Article Title: 

Stickler syndrome in children: a radiological review

McArthur N, Rehm A, Shenker N, Richards AJ, McNinch AM, Poulson AV, Tanner J, Snead MP, Bearcroft PWP. Stickler syndrome in children: a radiological review. Clin Radiol. 2018 Apr 13. pii: S0009-9260(18)30118-1. doi: 10.1016/j.crad.2018.03.004. [Epub ahead of print].

PubMed ID: 
29661559

High efficiency of mutation detection in type 1 stickler syndrome using a two-stage approach: vitreoretinal assessment coupled with exon sequencing for screening COL2A1

Richards AJ, Laidlaw M, Whittaker J, Treacy B, Rai H, Bearcroft P, Baguley DM, Poulson A, Ang A, Scott JD, Snead MP. High efficiency of mutation detection in type 1 stickler syndrome using a two-stage approach: vitreoretinal assessment coupled with exon sequencing for screening COL2A1. Hum Mutat. 2006 Jul;27(7):696-704. Erratum in: Hum Mutat. 2006 Nov;27(11):1156.

PubMed ID: 
16752401
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