macular atrophy

Chorioretinopathy with Microcephaly 2

Clinical Characteristics
Ocular Features: 

Microphthalmia and microcornea are seen in most individuals and one patient had unilateral clinical anophthalmia. Hyperopia and cataracts may be present. Nystagmus is common.  One patient had a corneal opacity.  The chorioretinopathy has not been described beyond evidence of the maculopathy, attenuated retinal vessels, and occasionally hyperpigmented zones.  The ERG is either not recordable or consistent with a severe rod-cone dystrophy.  Vitreous inclusions and a 'vitreoretinal dystrophy' with falciform retinal folds were noted in several patients.  A traction detachment was present in one and bilateral serous detachments were noted in another.

Systemic Features: 

Patients have mild to severe microcephaly (up to -15 SD) with psychomotor delays.  Profound intellectual disability is a consistent feature.  Physical growth is retarded and patients have shortness of stature.  Most patients are unable to sit, stand, or walk unassisted.  One patient died at 5.5 years of age while another was alive at 20 years of age.  Rare patients may have hearing loss and seizures.

Scoliosis, kyphosis, and lordosis may be seen while  other skeletal malformations seem to occur sporadically e.g., triphalangeal thumbs, brachydactyly, postaxial polydactyly, and restricted large joint motion.  

The forehead slopes markedly.  Neuroimaging shows a consistent reduction in cortex size with simple gyral folding while the cerebellum and the brain stem are also small.  Subarachnoid cysts have been noted in several patients and the corpus callosum may be short or otherwise malformed.

Genetics

Homozygous mutations in the PLK4 gene (4q28.2) segregate with this condition.  Its product localizes to centrioles and plays a central role in centriole duplication.

For a somewhat similar condition but without the sloping forhead see Chorioretinoapathy with Microcephaly 1 (251270) but resulting from homozygous mutations in TUBGCP6.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is know.

References
Article Title: 

Mutations in PLK4, encoding a master regulator of centriole biogenesis, cause microcephaly, growth failure and retinopathy

Martin CA, Ahmad I, Klingseisen A, Hussain MS, Bicknell LS, Leitch A, Nurnberg G, Toliat MR, Murray JE, Hunt D, Khan F, Ali Z, Tinschert S, Ding J, Keith C, Harley ME, Heyn P, Muller R, Hoffmann I, Daire VC, Dollfus H, Dupuis L, Bashamboo A, McElreavey K, Kariminejad A, Mendoza-Londono R, Moore AT, Saggar A, Schlechter C, Weleber R, Thiele H, Altmuller J, Hohne W, Hurles ME, Noegel AA, Baig SM, Nurnberg P, Jackson AP. Mutations in PLK4, encoding a master regulator of centriole biogenesis, cause microcephaly, growth failure and retinopathy. Nat Genet. 2014 Dec;46(12):1283-92.

PubMed ID: 
25344692

Retinitis Pigmentosa 38

Clinical Characteristics
Ocular Features: 

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

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

Systemic Features: 

None

Genetics

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

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

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

References
Article Title: 

Macular Edema, Autosomal Dominant Cystoid

Clinical Characteristics
Ocular Features: 

Only a few families have been reported.  The macular edema can be traced to retinal capillary leakage throughout the posterior pole as revealed by fluorescein angiography.  Scattered exudates and nerve fiber layer hemorrhages are sometimes seen.  Hyperopia and strabismus are often present as well.  Veils, strands, and white punctate deposits in the vitreous have been described.  Wrinkling of the internal limiting membrane may be present.  The ERG is normal except for elevated rod dark adaptation thresholds.  Light/dark ratios are abnormal on EOG testing and mild dyschromatopsia can be demonstrated.  Patients usually notice problems with their visual acuity in the second decade of life and it can drop to 20/200 at this time with progression to 2/120 - 2/200 in older individuals.  In later stages of the disease a central zone of beaten bronze macular atrophy can be seen.  Surrounding this central atrophy is often an area with pigmentary changes resembling retinitis pigmentosa which can extend into the periphery.

This would seem to be a unique disorder in spite of some similarities to retinitis pigmentosa in which macular cysts are often seen.  The clinical course is distinctly different and the presence of vitreous deposits and hyperopia also can be used as arguments for its separateness.  Molecular DNA evidence showing lack of allelism (Vida infra) is, of course the strongest evidence.

Systemic Features: 

No systemic abnormalities have been reported.

Genetics

This autosomal dominant form of progressive macular dystrophy is linked to a locus at 7p21-p15.  The mutation is close to the RP9 locus causing one type of retinitis pigmentosa but linkage analysis shows the two disorders to be non-allelic.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No specific treatment is available for the macular disease but low vision aids are likely useful, at least early in the disease.

References
Article Title: 

Gaucher Disease

Clinical Characteristics
Ocular Features: 

Gaucher disease is often divided into three clinical types, I, II, and III although all are caused by mutations in the same gene.  Type I, sometimes called nonneuronopathic type I, has ocular features including white deposits in anterior chamber structures such as the corneal endothelium, pupillary margin, and the angle, as well as in the ciliary body.  Pingueculae can be prominent.  The perimacular retina often appears grayish and also can show some white spots.  These may also be seen in the posterior vitreous in at least some patients with type III  There may be pigmentary changes in the macula and uveitis occurs rarely.  Macular atrophy has been reported and the retinal vasculature may be abnormally permeable. Corneal opacities have been seen in some patients.  Oculomotor apraxia and abnormal opticokinetic responses are common in types II and III.  Visual acuity may be in the range of 20/200.

Other conditions with ataxia and oculomotor apraxia are: ataxia with oculomotor apraxia 1 (208920), ataxia with oculomotor apraxia 2 (602600), ataxia-telangiectasia (208900) and Cogan-type oculomotor apraxia (257550) which lacks other neurologic signs.

Systemic Features: 

This is a severe systemic disease with perinatal lethality in some patients.  The range of clinical heterogeneity is wide, however, and minimally affected adult patients have also been described.  Individuals with nonneuropathic type I lack central nervous system involvement.  They often do have hepatosplenomegaly and pancytopenia with bone marrow involvement which are common to all types.  The latter may be responsible for frequent bone fractures and other orthopedic complications such as vertebral compression.  Thrombocytopenia with bleeding complications contributes to the primary anemia which is also present.  Interstitial lung disease can be seen in type I disease but occurs in less than 5% of patients. This is the most common of the three types. 

Patients with type I Gaucher disease have an increased risk of cancer, especially those of the hematological system.  For example, the risk for multiple myeloma has been estimated to be 37 times higher than in the general population.  There is also evidence of an increased incidence of multiple consecutive cancers in this condition.  Enzyme replacement therapy may reduce the risk of malignancies.

Patient with types II (acute neuronopathic [230900]) and III (subacute neuronopathic [231000]) are more likely to have neurologic disease with bulbar and pyramidal signs and sometimes seizures.  In type II, onset is in infancy and lifespan is about 2 years.   They have hepatosplenomegaly with growth arrest and developmental delays after a few months.  The clinical signs in type III or subacute neuronopathic type the onset is later (2.5 years to adulthood) than in type II and progression of neurologic disease is slower.  Early childhood development may appear normal for several years until abnormal extraocular movements or seizures are observed.  Type III is sometimes called Norrbottnian type.

Genetics

All three types of Gaucher disease are caused by mutations in the GBA (glucocerebrosidase) gene (1q21) and are inherited in an autosomal recessive pattern.

Evidence indicates that SCARB2, which codes for lysosomal integral membrane protein type 2 (LIMP-2), is a modifier of the phenotype in Gaucher disease.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Supportive care is required for all patients.  Splenectomy may be required for thrombocytopenia and blood transfusion can be helpful in severe anemia and excessive bleeding.  The course of disease is highly variable in all types, ranging from neonatal mortality to mild disease into adulthood, especially for individuals with type III.  Testing for deficiency in glucosylceramidase enzyme activity in leukocytes can be diagnostic.   Enzyme replacement or substrate reduction therapies can reduce the severity of clinical disease especially in type I disease but less so in types II and III.

References
Article Title: 

The clinical management of type 2 Gaucher disease

Weiss K, Gonzalez AN, Lopez G, Pedoeim L, Groden C, Sidransky E. The clinical management of type 2 Gaucher disease. Mol Genet Metab. 2014 Nov 14.  [Epub ahead of print] Review.

PubMed ID: 
25435509

A Mutation in SCARB2 is a Modifier in Gaucher Disease

Velayati A, Depaolo J, Gupta N, Choi JH, Moaven N, Westbroek W, Goker-Alpan O, Goldin E, Stubblefield BK, Kolodny E, Tayebi N, Sidransky E. A Mutation in SCARB2 is a Modifier in Gaucher Disease. Hum Mutat. 2011 Jul 27. doi: 10.1002/humu.21566. [Epub ahead of print]

PubMed ID: 
21796727

Bardet-Biedl Syndromes

Clinical Characteristics
Ocular Features: 

The term Bardet-Biedl is applied to a clinically and genetically diverse group of disorders, of which at least 21 entities (BBS1-BBS21) are recognized.  This discussion is generically relevant to all of the phenotypes since the retinal dystrophy is common to all.

A progressive rod-cone dystrophy is a cardinal feature of all forms of Bardet-Biedl syndrome.  However, a subset of patients have primary cone degeneration.  In at least some forms of this syndrome, the cause seems to be a defect in the cilia that impairs the intraciliary protein transport between the inner and outer segments of the photoreceptors.  Vision loss has an early onset and usually progresses rapidly with severe loss of central and peripheral vision by the second or third decade of life.  Night blindness may be evident by 7 or 8 years of age.  The ERG is not recordable even in early childhood.  Pigmentary changes in the retina are often labeled retinitis pigmentosa but they are atypical for the usual disease.  Early changes are more characteristic of atrophy with a paucity of pigment but later the bone spicule pattern of hyperpigmentation appears.  The macula can appear atrophic and sometimes has a bull's eye pattern.  Optic atrophy and retinal arteriole narrowing may be seen.  Bardet-Biedl syndrome is clinically similar to Biemond syndrome (210350) except for iris colobomas that occur in the latter disorder.

Systemic Features: 

Obesity, mental retardation, renal disease, and hepatic fibrosis with syndactyly, brachydactyly, and post-axial polydactyly are characteristic.  The degree of mental handicap varies widely.  Diabetes mellitus is present in about one-third of patients.  Structural deformities of genitalia as well as hypogonadism and menstrual irregularities often occur as in some other disorders but the association of severe vision loss and characteristic retinal changes are diagnostically helpful.  Kidney failure secondary to cystic nephronophthisis or other renal malformations is common. Hypercholesterolemia is found in many patients.  Many patients have motor difficulties, appearing clumsy and unsteady.  Emotional lability and inappropriate outbursts can be part of these syndromes as well.

Genetics

The syndromes of Bardet-Biedl are inherited in an autosomal recessive pattern.  At least 21 mutations have been identified.  Not all cases are caused by homozygosity of the same mutation since compound heterozygosity at two loci may also cause similar phenotypes.

Laurence-Moon syndrome (245800) is considered part of the Bardet-Biedl group of diseases in this database. 

Mutations in PNPLA6 have been found in some individuals with a form of Bardet-Biedl syndrome as well as in Boucher-Neuhauser Syndrome (215470) also known as Chorioretinopathy, Ataxia, Hypogonadism Syndrome, and Trichomegaly Plus Syndrome (275400), in this database.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment exists for these syndromes but organ specific therapy may be helpful.

Studies in a mice model suggest that the neural retina may at least partially recover in type 1 following subretinal injection of viral vectors containing the wild-type bbs1 gene.

 

References
Article Title: 

Bardet-Biedl Syndrome

Suspitsin EN, Imyanitov EN. Bardet-Biedl Syndrome. Mol Syndromol. 2016 May;7(2):62-71.

PubMed ID: 
27385362

Predominantly cone-system dysfunction as rare form of retinal degeneration in patients with molecularly confirmed Bardet-Biedl Syndrome

Scheidecker S, Hull S, Perdomo Y, Studer F, Pelletier V, Muller J, Stoetzel C, Schaefer E, Defoort-Dhellemmes S, Drumare I, Holder Graham E, Hamel Christian P, Webster Andrew R, Moore Anthony T, Puech B, Dollfus Helene J. Predominantly cone-system dysfunction as rare form of retinal degeneration in patients with molecularly confirmed Bardet-Biedl Syndrome. Am J Ophthalmol. 2015 May 14. [Epub ahead of print]. 

PubMed ID: 
25982971

Neuropathy target esterase impairments cause Oliver-McFarlane and Laurence-Moon syndromes

Hufnagel RB, Arno G, Hein ND, Hersheson J, Prasad M, Anderson Y, Krueger LA, Gregory LC, Stoetzel C, Jaworek TJ, Hull S, Li A, Plagnol V, Willen CM, Morgan TM, Prows CA, Hegde RS, Riazuddin S, Grabowski GA, Richardson RJ, Dieterich K, Huang T, Revesz T, Martinez-Barbera JP, Sisk RA, Jefferies C, Houlden H, Dattani MT, Fink JK, Dollfus H, Moore AT, Ahmed ZM. Neuropathy target esterase impairments cause Oliver-McFarlane and Laurence-Moon syndromes. J Med Genet. 2015 Feb;52(2):85-94.

PubMed ID: 
25480986

Mutations in IFT172 Cause Isolated Retinal Degeneration and Bardet-Biedl Syndrome

Bujakowska KM, Zhang Q, Siemiatkowska AM, Liu Q, Place E, Falk MJ, Consugar M, Lancelot ME, Antonio A, Lonjou C, Carpentier W, Mohand-Sayid S, den Hollander AI, Cremers FP, Leroy BP, Gai X, Sahel JA, van den Born LI, Collin RW, Zeitz C, Audo I, Pierce EA. Mutations in IFT172 Cause Isolated Retinal Degeneration and Bardet-Biedl Syndrome. Hum Mol Genet. 2014 Aug 28.  [Epub ahead of print].

PubMed ID: 
25168386
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