rod-cone dystrophy

Alström Syndrome

Clinical Characteristics

Ocular Features

Progressive failure of rods and cones begins in the first year of life and inevitably leads to blindness.  Central vision is lost first and nystagmus in early childhood results.   Photophobia can be evident in the first year of life.  Early ERGs show severe impairment of cone responses with little or no rod dysfunction.  In the second and third decades all rod and cone responses are extinguished.  Vision can be less than 20/400 by the age of 10 years and usually all light perception is lost by the beginning of the third decade.  Pale optic nerves with retinal arteriorlar narrowing and posterior subcapsular cataracts have been seen.

Systemic Features

This is a multisystem disease with onset in the first year of life.  Infants may have a normal birth weight but develop truncal obesity in the first year.  Hearing loss is evident in the first decade.  Insulin resistant type 2 diabetes mellitus with hyperinsulinemia often occurs in childhood and may be accompanied by hypothyroidism and hypogonadotropic hypogonadism.  Acanthosis nigricans and some degree of pulmonary dysfunction are common.  The majority of individuals (70%) develop restrictive or dilated cardiomyopathy, many in the first months of life, resulting in cardiac failure.  The liver may become cirrhotic and renal failure occurs late.  Intelligence is usually normal but many patients (25-30%) have early delays in their developmental milestones perhaps secondary to growth hormone deficiency which has been reported (98% are short in stature).  Lifespan is short and many die in childhood.  Few live beyond the age of 40 years.

Alström syndrome has some similarities to Bardet-Biedl syndrome (209900) but differs in the absence of mental deficiency and polydactyly.

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the ALMS1 gene on chromosome 2 (2p13).  More than 320 mutations have been reported. However, many cases remain in which no mutation has been found suggesting additional clinical heteorgeneity remains.

Treatment Options

No treatment is available for the basic disease.

References

Marshall JD, Muller J, Collin GB, Milan G, Kingsmore SF, Dinwiddie D, Farrow EG, Miller NA, Favaretto F, Maffei P, Dollfus H, Vettor R, Naggert JK. Alström Syndrome: Mutation Spectrum of ALMS1. Hum Mutat. 2015 Apr 2. doi: 10.1002/humu.22796. [Epub ahead of print].

PubMed ID: 
25846608

Marshall JD, Beck S, Maffei P, Naggert JK. Alstrom syndrome. Eur J Hum Genet. 2007 Dec;15(12):1193-202.

PubMed ID: 
17940554

Russell-Eggitt IM, Clayton PT, Coffey R, Kriss A, Taylor DS, Taylor JF. Alström syndrome. Report of 22 cases and literature review. Ophthalmology. 1998 Jul;105(7):1274-80. Review.

PubMed ID: 
9663233

Retinal Dystrophy, Newfoundland Type

Clinical Characteristics

Ocular Features

There is considerable clinical heterogeneity, mostly age-dependent.  Night blindness can occur in early childhood but usually later even though scotopic responses can be undetectable in the first decade of life while photopic responses are reduced on the ERG at all ages.  Both rod and cone responses may be extinguished in later life.  Visual acuity can be decreased beginning in early childhood and legal blindness usually occurs by the second or third decade of life.  However, the loss of vision continues to progress and severe vision loss to finger-counting may be present in older individuals.  A scallop-bordered lacunar atrophy may be seen in the midperiphery.  The macula is only mildly involved by clinical examination although central retinal thinning is seen in all cases.  Dyschromatopsia is mild early and usually becomes more severe.  The visual fields are moderately to severely constricted although in younger individuals a typical ring scotoma is present.  The peripheral retina contains ‘white dots’ and often resembles the retinal changes seen in retinitis punctate albescens.

Systemic Features

None reported.

Genetics

Homozygous mutations in the RLBP1 gene (15q26.1) are responsible for this disorder.  Homozygous mutations in RLBP1 have also been found among patients with fundus albipunctatus (136880), retinitis punctata albescens, and in Bothnia type retinal dystrophy (607475),

NFRCD clinically resembles Bothnia type retinal dystrophy (607475) which likewise results from mutations in the RLBP1 gene but the maculae appear normal or have only a mild ‘beaten-bronze’ atrophy.

See Flecked Retina entry for somewhat similar conditions.

Treatment Options

No treatment is known.

References

Hipp S, Zobor G, Glöckle N, Mohr J, Kohl S, Zrenner E, Weisschuh N, Zobor D. Phenotype variations of retinal dystrophies caused by mutations in the RLBP1 gene. Acta Ophthalmol. 2014 Nov 27.  [Epub ahead of print].

PubMed ID: 
25429852

Eichers ER, Green JS, Stockton DW, Jackman CS, Whelan J, McNamara JA, Johnson GJ, Lupski JR, Katsanis N. Newfoundland rod-cone dystrophy, an early-onset retinal dystrophy, is caused by splice-junction mutations in RLBP1. Am J Hum Genet. 2002 Apr;70(4):955-64.

PubMed ID: 
11868161

Retinal Dystrophy and Obesity

Clinical Characteristics

Ocular Features

The age of onset of symptoms is unknown but based on the report of a single family with three affected sibs, it may occur early in the second decade. Patients may note some loss of night vision and the visual fields are restricted.  The ERG responses are consistent with a generalized rod-cone dystrophy.  Fundoscopy reveals a generalized RPE atrophy together with arteriolar attenuation, peripheral pigmentary mottling and scattered white dots.  A nonspecific dyschromatopsia can be demonstrated but the fovea is relatively normal and central acuity is remarkably good.  Little is known about disease progression but an 18 year old male reported decreasing vision since the age of 11 years.  

Systemic Features

Obesity and a high BMI may be present.

Genetics

Homozygous mutations in the TUB gene (11p15) segregated with this disorder in a sibship from a consanguineous family.

Treatment Options

No treatment has been reported.

References

Borman AD, Pearce LR, Mackay DS, Nagel-Wolfrum K, Davidson AE, Henderson R, Garg S, Waseem NH, Webster AR, Plagnol V, Wolfrum U, Farooqi IS, Moore AT. A homozygous mutation in the TUB gene associated with retinal dystrophy and obesity. Hum Mutat. 2014 Mar;35(3):289-93.

PubMed ID: 
24375934

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).

Treatment Options

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

References

Ksantini M, Lafont E, Bocquet B, Meunier I, Hamel CP. Homozygous mutation in MERTK causes severe autosomal recessive retinitis pigmentosa. Eur J Ophthalmol. 2012 Jul-Aug;22(4):647-53.

PubMed ID: 
22180149

Mackay DS, Henderson RH, Sergouniotis PI, Li Z, Moradi P, Holder GE, Waseem N, Bhattacharya SS, Aldahmesh MA, Alkuraya FS, Meyer B, Webster AR, Moore AT. Novel mutations in MERTK associated with childhood onset rod-cone dystrophy. Mol Vis. 2010 Mar 9;16:369-77.

PubMed ID: 
20300561

Retinitis Pigmentosa, Hearing Loss, Ataxia, Cataract, and Polyneuropathy

Clinical Characteristics

Ocular Features

Cataracts and a pigmentary retinopathy occur in this condition but only in some, primarily older, patients.  The lens opacities progress and may become visually significant by the third decade.  Bone-spicule-shaped pigment clumping may be present in the midperiphery while the optic disk is often pale and the retinal vessels are attenuated. The ERG responses are consistent with a rod-cone dystrophy.

Systemic Features

This is a progressive neurological disorder with onset of signs and symptoms in childhood although full expression may not occur until adulthood.  Young children can have hyporeflexia, pes cavus, spasticity, and gait ataxia.  A sensorineural hearing loss may also be present in childhood but sometimes not until later.  Hyperreflexia with extensor plantar responses and Achilles tendon contractures are often present later.  The peripheral polyneuropathy is predominantly demyelinating with both sensory and motor components and is present in all adults.  Cerebellar atrophy, primarily in the vermis, can be demonstrated on MRI examination.  Mental function is usually not impaired. Some patients have dysarthria. 

This disorder has some clinical similarities to Refsum disease (266500).

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the ABHD12 gene (20p11.21).

Treatment Options

Treatment is directed at symptoms.  Visually significant cataracts may require removal.  Low vision aids and physical therapy can be helpful.

References

Fiskerstrand T, H'mida-Ben Brahim D, Johansson S, M'zahem A, Haukanes BI, Drouot N, Zimmermann J, Cole AJ, Vedeler C, Bredrup C, Assoum M, Tazir M, Klockgether T, Hamri A, Steen VM, Boman H, Bindoff LA, Koenig M, Knappskog PM. Mutations in ABHD12 cause the neurodegenerative disease PHARC: An inborn error of endocannabinoid metabolism. Am J Hum Genet. 2010 Sep 10;87(3):410-7.

PubMed ID: 
20797687

Fiskerstrand T, Knappskog P, Majewski J, Wanders RJ, Boman H, Bindoff LA. A novel Refsum-like disorder that maps to chromosome 20. Neurology. 2009 Jan 6;72(1):20-7.

PubMed ID: 
19005174

Retinal Dystrophy, Bothnia Type

Clinical Characteristics

Ocular Features

Night blindness occurs from early childhood when the fundus still appears normal.  However, rod responses may be absent from ERG recordings even in the first decade and this is followed by loss of cone responses in older individuals. Rod responses can recover after prolonged dark adaptation but cone function does not recover.  Multifocal ERGs can detect early deterioration of the macula while vision and the appearance of the macula are still normal.

Pigment deposition can sometimes be seen in the retina and the retinal blood vessels may be attenuated.  In young adults the fundus may have the appearance of retinitis albescens but eventually changes resembling central areolar atrophy develop in the macula.  Retinal thinning in the fovea and parafoveal areas has been described.  Progressive loss of vision leads to legal blindness in early adulthood.  The peripheral retina undergoes degenerative changes as well.

Systemic Features

No extraocular abnormalities have been reported.

Genetics

Homozygous mutations in the RLBP1 gene (15q26.1) have been identified in patients with Bothnia retinal dystrophy.  The protein product is essential to the proper function of both rod and cone photoreceptors.  When defective the normal cycling of retinoids between RPE cells and photoreceptors is disrupted, thereby negatively impacting what is sometimes called the 'visual cycle'. 

This rod-cone dystrophy has a high prevalence in northern Sweden.

Homozygous mutations in RLBP1 have also been found among patients in fundus albipunctatus (136880), retinitis punctata albescens, and in Newfoundland type retinal dystrophy (607476).

Treatment Options

None has been reported. Tinted lenses can be helpful.

References

Burstedt M, Jonsson F, Köhn L, Burstedt M, Kivitalo M, Golovleva I. Genotype-phenotype correlations in Bothnia dystrophy caused by RLBP1 gene sequence variations. Acta Ophthalmol. 2012 May 2. doi: 10.1111/j.1755-3768.2012.02431.x. [Epub ahead of print]

PubMed ID: 
22551409

Gränse L, Abrahamson M, Ponjavic V, Andréasson S. Electrophysiological findings in two young patients with Bothnia dystrophy and a mutation in the RLBP1 gene. Ophthalmic Genet. 2001 Jun;22(2):97-105

PubMed ID: 
11449319

Burstedt MS, Forsman-Semb K, Golovleva I, Janunger T, Wachtmeister L, Sandgren O. Ocular phenotype of bothnia dystrophy, an autosomal recessive retinitis pigmentosa associated with an R234W mutation in the RLBP1 gene. Arch Ophthalmol. 2001 Feb;119(2):260-7.

PubMed ID: 
11176989

Optic Nerve Edema, Splenomegaly, Cytopenias

Clinical Characteristics

Ocular Features

Persistent optic nerve edema is eventually followed by some degree of optic atrophy.  The nerve edema may be seen early in the first decade of life and is not associated with increased lumbar puncture pressure.  Peripapillary hemorrhages may be seen.  Visual acuity may decrease somewhat by the end of the first decade of life and becomes functionally significant in early adolescence and may be reduced to counting fingers.  The ERG, which shows minimal dysfunction early, eventually appears nearly flat without photopic or scotopic responses.  The retinal vessels become markedly attenuated and the macula may be mildly edematous and show pigmentary changes.  Pigment clumping is not seen.  Visual fields show a central or cecocentral scotoma, enlargement of the blind spot, and eventually severe peripheral constriction.  The vitreous and aqueous humor sometimes have an increased number of cells.   Lenticular opacities requiring cataract surgery has been reported.  One patient developed a phacomorphic angle closure attack at the age of 19 years.

Systemic Features

Splenomegaly is a consistent sign and is usually present in the first decade of life but histology shows primarily cellular congestion of the red pulp cords.  Bone marrow biopsies show mild erythroid hyperplasia. Peripheral blood counts show mild neutropenia and thrombocytopenia.  Occasional atypical lymphocytes may be seen.  Patients often complain of mildly to moderately severe migraine headaches.  Urticaria and anhidrosis are common features.

Genetics

Only a single report of this condition has been published.  A mother and two daughters (half sisters) had the symptoms described here and this is the basis for consideration of autosomal dominant inheritance.  Nothing is known regarding the etiology or the mechanism of disease.

Treatment Options

Topical, intravitreal, oral, and subtenon application of steroids apparently have no impact on the progression of the intraocular disease.  Cataracts may need to be removed.

References

Tantravahi SK, Williams LB, Digre KB, Creel DJ, Smock KJ, Deangelis MM, Clayton FC, Vitale AT, Rodgers GM. An inherited disorder with splenomegaly, cytopenias, and vision loss. Am J Med Genet A. 2012 Mar;158A(3):475-81. doi: 10.1002/ajmg.a.34437. Epub 2012 Feb 3.

PubMed ID: 
22307799

Spinocerebellar Ataxia 1

Clinical Characteristics

Ocular Features

Early manifestations include gaze-evoked nystagmus and saccadic hypermetria.  Ophthalmoplegia develops later in the disease process.  Some patients experience a decrease in acuity and dyschromatopsia.  The ERG shows evidence of generalized rod and cone photoreceptor dysfunction in some patients.  Optic atrophy, central scotomas, central RPE changes, retinal arteriolar attenuation, and blepharospasm have also been reported.

Time-domain OCT has revealed microscopic changes in the macula with thinning of the inner-outer segment junction and nuclear layer in areas with RPE hypopigmentation. 

Systemic Features

This is a progressive cerebellar syndrome characterized by systems of ataxia, dysarthria, and bulbar palsy.  Speech is often scanning and explosive.  DTRs can be exaggerated, and dysmetria is common.  The mean age of onset is about age 40.  Some cognitive decline may occur.  Muscle atrophy, and symptoms of peripheral neuropathy can be present.  MRI shows atrophy in the cerebellum, spinal cord, and brainstem.  There is considerable variation in clinical expression.  Individuals with adult onset of symptoms can survive for 10-30 years whereas those with a juvenile-onset often do not live beyond the age of 16 years.

Genetics

This disorder is caused by an expanded CAG repeat in the ataxin-1 gene (ATXN1) at 6p23.  It is an autosomal dominant disorder.  Alleles with 39-44 or more CAG repeats are likely to be associated with symptoms. 

A male bias and the phenomenon of anticipation have been demonstrated in this disorder as in spinocerebellar ataxia 7 (SCA7) (164500), in which affected offspring of males with SCA develop disease earlier and symptoms progress more rapidly than in offspring of females.  This is often explained by the fact that males generally transmit a larger number of CAG repeats.

SCA7 (164500), also inherited in an autosomal dominant pattern and caused by expanded CAG repeats on chromosome 3, has many similar ocular and neurologic features.

Treatment Options

Supportive care is often required.          

References

Lebranchu P, Le Meur G, Magot A, David A, Verny C, Weber M, Milea D. Maculopathy and Spinocerebellar Ataxia Type 1: A New Association? J Neuroophthalmol. 2013 Apr 11. [Epub ahead of print]

PubMed ID: 
23584155

Vaclavik V, Borruat FX, Ambresin A, Munier FL. Novel maculopathy in patients with spinocerebellar ataxia type 1 autofluorescence findings and functional characteristics. JAMA Ophthalmol. 2013 Apr 1;131(4):536-8.

PubMed ID: 
23579607

Thurtell MJ, Biousse V, Newman NJ. Rod-cone dystrophy in spinocerebellar ataxia type 1. Arch Ophthalmol. 2011 Jul;129(7):956-8.

PubMed ID: 
21746990

Bürk K, Fetter M, Abele M, Laccone F, Brice A, Dichgans J, Klockgether T. Autosomal dominant cerebellar ataxia type I: oculomotor abnormalities in families with SCA1, SCA2, and SCA3. J Neurol. 1999 Sep;246(9):789-97.

PubMed ID: 
10525976

Buttner N, Geschwind D, Jen JC, Perlman S, Pulst SM, Baloh RW. Oculomotor phenotypes in autosomal dominant ataxias. Arch Neurol. 1998 Oct;55(10):1353-7.

PubMed ID: 
9779665

Rivaud-Pechoux S, Dürr A, Gaymard B, Cancel G, Ploner CJ, Agid Y, Brice A, Pierrot-Deseilligny C. Eye movement abnormalities correlate with genotype in autosomal dominant cerebellar ataxia type I. Ann Neurol. 1998 Mar;43(3):297-302. Review.

PubMed ID: 
9506545

Stricker S, Oberwahrenbrock T, Zimmermann H, Schroeter J, Endres M, Brandt AU, Paul F. Temporal retinal nerve fiber loss in patients with spinocerebellar ataxia type 1. PLoS One. 2011;6(7):e23024. Epub 2011 Jul 29.

PubMed ID: 
21829579

Oculoauricular Syndrome

Clinical Characteristics

Ocular Features

This rare malformation syndrome affects primarily the eyes and ears.  The globes are small and usually have colobomas of both anterior and posterior segments.  The corneas likewise are small and often have opacities.  The anterior segment is dysplastic with anterior and/or posterior synechiae.  Glaucoma may be present.  The lenses may be small and often become cataractous.  There is a progressive rod-cone dystrophy associated with a pigmentary retinopathy.  Chorioretinal lacunae have been seen in the equatorial region.  The retinal degeneration is progressive, beginning with rod dysfunction but followed by deterioration of all receptors.  The onset in early childhood results in poor vision and nystagmus. 

Systemic Features

The external ears are abnormal.  The earlobes may have colobomas or may be aplastic.  The intertragic notch is often underdeveloped.  Audiograms and vestibular function tests, however, show normal function and MRI of the middle and inner ears likewise reveals no anatomic abnormalities.       

Among the few patients reported, dental anomalies, spina bifida oculta, and mild dyscrania have been noted in individual patients.

Genetics

This rare disorder has been reported in only a few families.  Based on parental consanguinity and homozygosity of mutations in the HMX1 gene (4p16.1) in affected sibs, this is an autosomal recessive disorder.  In one family there was a homozygous 26 bp deletion and in another a homozygous missense mutation.  The parents are heterozygous for the deletion.

HMX1 is a homeobox gene and the deletion abolishes its function by establishing a stop codon at position 112.

Treatment Options

No treatment is available for the extraocular malformations.  Glaucoma treatment and cataract surgery should be considered although permanent visual rehabilitation is unlikely given the progressive nature of the rod-cone dystrophy.

References

Gillespie RL, Urquhart J, Lovell SC, Biswas S, Parry NR, Schorderet DF, Lloyd IC, Clayton-Smith J, Black GC. Abrogation of HMX1 Function Causes Rare Oculoauricular Syndrome Associated With Congenital Cataract, Anterior Segment Dysgenesis, and Retinal Dystrophy. Invest Ophthalmol Vis Sci. 2015 Jan 8;56(2):883-91.

PubMed ID: 
25574057

Vaclavik V, Schorderet DF, Borruat FX, Munier FL. Retinal Dystrophy In The Oculo-auricular Syndrome Due to HMX1 Mutation. Ophthalmic Genet. 2011 Jun;32(2):114-7.

PubMed ID: 
21417677

Schorderet DF, Nichini O, Boisset G, Polok B, Tiab L, Mayeur H, Raji B, de la Houssaye G, Abitbol MM, Munier FL. Mutation in the human homeobox gene NKX5-3 causes an oculo-auricular syndrome. Am J Hum Genet. 2008 May;82(5):1178-84.

PubMed ID: 
18423520

Warburg Micro Syndrome 1

Clinical Characteristics

Ocular Features

Microphthalmia with microcornea, lens opacities, small and unresponsive pupils, and optic atrophy are the outstanding ocular features of this syndrome. Some but not all have ERG evidence of rod and cone dysfunction.  The VEP is usually abnormal.  Short palpebral fissures have been described. 

Systemic Features

Patients with the micro syndrome have many somatic and neurologic abnormalities.  Some degree of psychomotor retardation and developmental delays is common.  Both spasticity and hypotonia have been described.  Some patients have seizures.  Facial hypertrichosis, anteverted ears, and a broad nasal bridge are often noted.   There may be absence of the corpus callosum while diffuse cortical and subcortical atrophy and pachygyria may be evident on MRI imaging.  Hypogenitalism in males has been described.  Microcephaly is inconsistently present. 

Genetics

This disorder is caused by homozygous mutations in the RAB3GAP1 gene (2q21.3) and therefore inherited in an autosomal recessive pattern.

At least three other forms of Warburg Micro Syndrome have been reported: WARBM2 (614225) caused by homozygous mutations in RAB3GAP2, WARBM3 (614222) resulting from homozygous mutations in RAB18, and WARBM4 (615663) secondary to homozygous mutations in TBC1D20.  

Treatment Options

No effective treatment is available.  Vision remains subnormal even after cataracts are removed. 

References

Handley MT, Carpanini SM, Mali GR, Sidjanin DJ, Aligianis IA, Jackson IJ, FitzPatrick DR. Warburg Micro syndrome is caused by RAB18 deficiency or dysregulation. Open Biol. 2015 Jun;5(6). pii: 150047. doi: 10.1098/rsob.150047. 

PubMed ID: 
26063829

Morris-Rosendahl DJ, Segel R, Born AP, Conrad C, Loeys B, Brooks SS, Müller L,Zeschnigk C, Botti C, Rabinowitz R, Uyanik G, Crocq MA, Kraus U, Degen I, Faes F. New RAB3GAP1 mutations in patients with Warburg Micro Syndrome from different ethnic backgrounds and a possible founder effect in the Danish. Eur J Hum Genet. 2010 Oct;18(10):1100-6.

PubMed ID: 
20512159

Abdel-Salam GM, Hassan NA, Kayed HF, Aligianis IA. Phenotypic variability in Micro syndrome: report of new cases. Genet Couns. 2007;18(4):423-35.

PubMed ID: 
18286824

Warburg M, Sjö O, Fledelius HC, Pedersen SA. Autosomal recessive microcephaly, microcornea, congenital cataract, mental retardation, optic atrophy, and hypogenitalism. Micro syndrome. Am J Dis Child. 1993 Dec;147(12):1309-12.

PubMed ID: 
8249951