autosomal recessive

Fleck Retina, Benign Familial

Clinical Characteristics
Ocular Features: 

The appearance of the retina is said to be distinctive.  Bright, discrete yellow-white dots or fish-tail flecks are seen extending from the parafoveal region to the periphery where they may be larger and more confluent.  The central macula is spared.  The flecks autofluoresce and fluorescein angiography reveals mild irregular hyperfluorescence.  These have been described in multiple asymptomatic patients during the first decade of life and might be congenital in origin.  Photopic and scotopic vision remains normal and no ERG or EOG abnormalities can be recorded. The retinal pigment epithelium and vasculature are normal.

Systemic Features: 

No systemic disease is present.

Genetics

This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in the PLA2G5 gene located at 1p36.13-p36.12.

Retinal flecks can be seen in a number of hereditary retinal syndromes (see FLecked Retina Syndromes).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is necessary.

References
Article Title: 

Flecked-retina syndromes

Walia S, Fishman GA, Kapur R. Flecked-retina syndromes. Ophthalmic Genet. 2009 Jun;30(2):69-75..

PubMed ID: 
19373677

Spastic Paraplegia 15

Clinical Characteristics
Ocular Features: 

Yellowish flecks resembling those seen in fundus flavimaculatus are present, primarily in the macular area.   These can be present in large numbers in homozygotes with the full neurological syndrome.  Background retinal pigmentation appears clinically normal but fluorescein angiography shows a strikingly mottled picture with areas of hyper- and hypofluorescence.  Retinal flecks have also been reported in heterozygous parents.

The central macula exhibits autofluorescence.  Standard EOG and ERG recordings are normal but multifocal electroretinography shows subnormal responses in the macular area.  Visual acuity is minimally impacted.

Systemic Features: 

This is a form of spastic paraplegia with progressive spasticity primarily affecting the lower limbs.  Mental retardation (or at least cognitive impairment), dysarthria, a thin corpus callosum, and distal amyotrophy are often present.  Hearing deficits have also been described.  Some but not all patients have tremors, cerebellar ataxia, epilepsy and behavioral disturbances. Onset is between 10 and 19 years of age.  Little is known about the rate of symptom progression.

Genetics

This is an autosomal recessive disorder resulting from mutations in the ZFYVE26 gene (14q24.1).

Spastic paraplegia 7 (607259) has similar neurological features but with ptosis, optic atrophy, and nystagmus.  Congenital cataracts occur in addition to the neurological signs in spastic paraplegia 46 (614409) .

Other disorders with retinal flecks are described in Flecked Retina Syndromes.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Fleck retina in Kjellin's syndrome

Farmer SG, Longstreth WT Jr, Kalina RE, Todorov AB. Fleck retina in Kjellin's syndrome. Am J Ophthalmol. 1985 Jan 15;99(1):45-50.

PubMed ID: 
3966518

Canavan Disease

Clinical Characteristics
Ocular Features: 

Optic atrophy is the primary and perhaps only ocular manifestation of Canavan disease.  Acuity levels have not been reported but it has been noted that some infants and young children with early onset severe disease are able to track targets.  The ocular phenotype has not been well delineated.

Systemic Features: 

The clinical diagnosis of Canavan disease is suggested when the triad of hypotonia, macrocephaly and head lag is present.  It is a progressive form of spongy degeneration of the central nervous system but its onset, course, and severity are variable.

The disease is often evident before 6 months of age and survival is limited to a few months or years in infants with such early onset.  Such patients have the most severe and rapidly progressive disease.  It is noteworthy that, even though such infants do not achieve normal milestones such as sitting and standing, they do often interact socially by laughing, smiling, and reaching for objects.  Most young children are quiet and apathetic but some become irritable and develop spasticity as they grow.  CNS damage is evident as leukodystrophy on neuroimaging studies but this may not be present in later onset, milder forms of the disease.         

Other individuals may have a later and milder juvenile onset of symptoms and may present with delayed speech or motor development late in the first decade.  They often attend regular school but may benefit from tutoring and speech therapy.  They may live to adolescence or early adulthood.  Maldevelopment of the organ of Corti is responsible for hearing deficits in some children.

Genetics

Canavan disease is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in the gene (ASPA) located at 17p13.2 encoding the enzyme aspartoacylase.  N-acetylaspartic acid (NAA) levels are usually elevated in urine.  However, because the levels of NAA can vary depending on the severity of clinical disease, gene testing provides a more reliable diagnosis. 

The carrier frequency is high among members of the Ashkenazi Jewish population.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Antiepileptic drugs can be helpful.  Augmented feeding (gastric tubes)may be needed to maintain nutrition, while physical therapy and exercise may prevent contractures.  Speech therapy and low vision aids might be of benefit. Rare patients with a hearing deficit should be evaluated for possible benefit of hearing aids.

References
Article Title: 

Fundus Albipunctatus

Clinical Characteristics
Ocular Features: 

This disorder is often considered to belong to the category of retinal disease known as flecked retina syndrome.  Further, the nomenclature is not standardized and varying names have been attached to the more or less characteristic fundus picture consisting of uniformly distributed small yellow-white dots in the retina.  These tend to be concentrated in the midperiphery.  The macula usually is not involved in young people although ERG evidence suggests some worsening of cone dysfunction with age and central acuity may be decreased in midlife.  Frank macular degeneration has been seen clinically .  Delayed dark adaptation can be demonstrated with delays in recovery of rod and cone function.  Patients complain of night blindness beginning in childhood with little evidence of progression.

The disease known as retinitis punctata albescens (136880) may or may not be a unique disorder.  It is sometimes grouped with fundus albipunctatus while others consider it to be a separate entity.  Evidence for its uniqueness is based on the progressive nature of field loss and the presence of pigmentary changes and retinal vascular attenuation which are not found in fundus albipunctatus.  Further, the scotopic ERG waveforms usually do not regenerate.  More discriminating studies, especially genotyping, will likely provide additional information.  It would also be useful to have additional follow-up information on families. 

Systemic Features: 

No systemic disease is associated.

Genetics

Fundus albipunctatus is a genetically heterogeneous disorder.  Mutations in two genes, PRPH2 (6p21.1) and RDH5 (12q13.2) have been found among families.  The inheritance pattern for families with mutations in PRPH2 is consistent with autosomal dominant inheritance while mutations in RDH5 result in an autosomal recessive pattern.  Mutations in RLBP1 have also been found in some families.

Gene studies so far have not been helpful in discriminating between fundus albipunctatus and retinitis punctata albescens (136880).  For example, RLBP1 mutations have been identified among members of the same kindred having the clinical diagnosis of retinitis punctata albescens (136880) among older individuals while younger patients had features of fundus albipunctatus.  Further, the latter disorder has also been described among families with mutations in PRPH2 and RHO hinting at further genetic heterogeneity.

A similar clinical picture may be seen in Bietti crystalline corneoretinopathy (210370), Bardet-Biedl syndrome (209900), and hyperoxaluria (259900).  More information on flecked retina syndromes may be found at Flecked Retina Syndromes.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available to restore full receptor cell function.  However, high oral doses of beta-carotene may lead to an improvement in night blindness. Low vision aids could be beneficial when central acuity is damaged.

References
Article Title: 

Persistent Hyperplastic Primary Vitreous

Clinical Characteristics
Ocular Features: 

Persistence and hyperplasia of the embryonic vitreous in most individuals results in significant ocular morbidity.  It results from a transcription factor deficiency in retinal ganglion cells which in turn negatively impacts development of the retinal vasculature.  As a consequence, the fetal hyaloid vasculature fails to regress and its persistence leads to a retrolental mass.

PHPV usually occurs unilaterally and affected eyes are generally blind from birth. Leukocoria secondary to the presence of a retrolental fibrovascular stalk is easily visible.  Nystagmus is frequently present and some patients have microphthalmos. The anterior segment may also be involved as evidenced by the presence of peripheral anterior synechiae, corneal opacities, cataracts, and glaucoma.  Contracture of the retrolental tissue In the posterior chamber results in the ciliary processes being pulled centrally and can lead to hemorrhage and retinal detachment. 

The clinical manifestations can make it difficult to distinguish from Norrie disease.

Systemic Features: 

No consistent systemic signs have been reported in PHPV individuals.

Genetics

The majority of PHPV cases occur sporadically, but families with transmission patterns compatible with both autosomal recessive and autosomal dominant patterns have been reported.

A six-generation family has been reported in which affected members had homozygous mutations in ATOH7 (10q21.3).  Based on mouse studies, this gene is expressed in the developing optic cup at the time that coincides with retinal ganglion cell formation.  Mice with absence of functioning Atoh7 lack retinal ganglion cells and optic nerves and develop PHPV.

A single family with presumed bilateral PHPV in 3 generations in a pattern consistent with autosomal dominant inheritance has been reported (611308).  However, no genotyping was reported and only the proband and his father had ophthalmologic examinations.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

No medical or surgical treatment is effective.  The majority of individuals have no light perception.

References
Article Title: 

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).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

None has been reported. Tinted lenses can be helpful.

References
Article Title: 

Myopia, AR, with Cataracts and Vitreoretinal Degeneration

Clinical Characteristics
Ocular Features: 

Axial myopia and poor vision are noted during childhood.  Most individuals have refractive errors in the range of-5 to -18 diopters with a mean spherical equivalent of -11.3 diopters.  The axial length ranges from 25.1 and 30.5 mm.  Peripheral vitreoretinal degeneration and cataracts are usually present after the onset of myopia.  Lenticular opacities may necessitate cataract surgery in 11 of the 13 myopic patients in one kindred, usually by the second decade of life.  Lens instability or frank subluxation was noted in 8 patients.  At least five eyes suffered retinal detachments secondary to retinal dialyses and blindness of at least one eye occurred in 23% of patients.

Systemic Features: 

Deafness was reported in a single patient.

Genetics

This condition results from homozygous mutations in the gene LEPREL1 (3q28) encoding prolyl 3-hydroxylase.  It was identified in a large consanguineous Israeli Bedouin kindred containing seven affected males and 6 affected females.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cataract and retinal surgery may be indicated. However, the instability of the lens can lead to complications. The nature and location of retinal tears likewise make repairs difficult and blindness is a relatively frequent complication.

References
Article Title: 

GM3 Synthase Deficiency

Clinical Characteristics
Ocular Features: 

Profound optic atrophy is the primary ocular feature in this disorder.  ERG amplitudes are normal.  Visual impairment is pronounced with no reactions to environmental stimuli but it is not possible to determine how much of this is due to general CNS disease.  Eye movements are random and uncoordinated. 

Systemic Features: 

Infants may appear normal at birth but within a few months develop signs of developmental stagnation with onset of tonic-clonic seizures.  Irritability, poor feeding, vomiting and failure to thrive are important features.  Generalized hypotonia is evident but lower limb deep tendon reflexes may be present.  Normal developmental milestones are never achieved and patients are unresponsive to their environment.  Older individuals develop non-purposeful choreothetoid movements.  The EEG shows multifocal epileptiform discharges and brain MRIs show diffuse atrophy in older patients.         

Genetics

This is an autosomal recessive disorder secondary to homozygous mutations in SIAT9 (ST3GAL5) (2p11.2).  It has so far been found only among members of several Old Order Amish isolates.

The nonsense mutation results in a deficiency of functional GM3 synthase important in the utilization of lactosylceramide necessary for the production of downstream gangliosides.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no known treatment for the enzyme deficiency.  Seizures respond poorly to anti-epileptic medications.

References
Article Title: 

Friedreich Ataxia 1

Clinical Characteristics
Ocular Features: 

Nystagmus and optic atrophy are important ocular signs.  The visual pathway, both anterior and posterior, is consistently involved and field defects are common even though many patients are asymptomatic.  OCT usually shows a reduced nerve fiber layer secondary to loss of axons.  About half of patients have abnormal visual evoked potentials.  A few patients experience a sudden loss of central vision during the second decade of life.

Systemic Features: 

Friedreich ataxia is a progressive neurodegenerative disorder with onset before puberty.  The spinocerebellar tracts, dorsal columns, pyramidal tracts, cerebellum, medulla, and optic radiation, may all be involved.  The outstanding symptom is ataxia with prominent involvement of gait and limbs.  Muscle weakness, extensor plantar responses, and absent lower limb reflexes are usually present.  Dysarthria is usually notable.  Sensory signs include impairment of position and vibratory senses.  ‘Twitching’ in limbs and digits is often noted and ‘restless leg syndrome’ is common.

Secondary changes include pes cavus, scoliosis, and hammer toe.  Cardiac disease is frequently present and heart failure is the most common cause of death.  Most patients have hypertrophic cardiomyopathy with characteristic EKG changes and some have subaortic stenosis as part of the hypertrophied myocardium.  Diabetes mellitus is present in 20-25%.  Some hearing loss occurs in more than 10% of individuals.

Most patients require a wheelchair within 15 years of disease onset and the mean age of death is about 36 years.

Rare patients with a later onset of FRDA retain lower limb deep tendon reflexes.

Genetics

Homozygous mutations in FXN (9p21.11) are responsible for Friedreich ataxia.  The most common DNA abnormality is a GAA trinucleotide repeat expansion in intron 1.  The number of repeats in patients is 70 to more than 1000 compared with 5-30 in normal individuals.  FXN encodes the mitochondrial protein frataxin.

About 2% of individuals have point mutations in FXN instead of trinucleotide repeats.

Some of the phenotypic variations may be explained by differences in the number of GAA repeats.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Treatment is largely directed at symptoms including speech and physical therapy and mobility assistive devices. Scoliosis may require surgical intervention.

References
Article Title: 

Visual system involvement in patients with Friedreich's ataxia

Fortuna F, Barboni P, Liguori R, Valentino ML, Savini G, Gellera C, Mariotti C, Rizzo G, Tonon C, Manners D, Lodi R, Sadun AA, Carelli V. Visual system involvement in patients with Friedreich's ataxia. Brain. 2009 Jan;132(Pt 1):116-23.

PubMed ID: 
18931386

Friedreich ataxia: an overview

Delatycki MB, Williamson R, Forrest SM. Friedreich ataxia: an overview. J Med Genet. 2000 Jan;37(1):1-8. Review.

PubMed ID: 
10633128

Spastic Ataxia 6, Charlevoix-Saguenay Type

Clinical Characteristics
Ocular Features: 

Patches of myelinated axons from retinal neurons in the retina are not unusual in the general population but are especially prominent among families in Canada with SPAX6.  These typically appear as striated white or yellowish-white patches with ‘fuzzy’ borders in the nerve fiber layer of the retina and radiate from the disc.  These findings are usually of no functional significance but if sufficiently large and dense can be demonstrated on perimetry as small scotomas.  The retinal nerve fiber layer may be 'hypertrophied' outside the areas of myelination.   Horizontal gaze nystagmus and deficits in conjugate pursuit movements are often present.   

Systemic Features: 

This neurodegenerative disorder begins in early childhood (12-18 months) with signs of cerebellar ataxia, pyramidal signs, and peripheral neuropathy.  Slightly older children develop a mixed-sensorimotor peripheral neuropathy. Dysarthria, limb spasticity, distal muscle wasting, and mitral valve prolapse are often present.  Knee reflexes are exaggerated while ankle reflexes are often absent.  Extensor plantar responses are usually present.  The EMG can show signs of denervation with slowed conduction while brain neuroimaging demonstrates regional atrophy in the cerebellum, especially the superior vermis.  Most patients eventually become wheelchair-bound.  However, cognitive and daily living skills are preserved into adulthood.  Most patients live into the sixth decade.

Genetics

Homozygous or compound heterozygous mutations in the SACS gene (13q12.12) are responsible for this autosomal recessive disorder.

The largest number of cases is found in the Charlevoix-Saguenay region of Quebec, Canada among the descendents of a founder but families have also been found in Asia and Europe.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment for the general disease is available but specific therapies for some functions such as urinary urgency are available.  Physical and speech therapy as well as special education assistance can be helpful for adaptation.

References
Article Title: 

Location score and haplotype analyses of the locus for autosomal recessive spastic ataxia of Charlevoix-Saguenay, in chromosome region 13q11

Richter A, Rioux JD, Bouchard JP, Mercier J, Mathieu J, Ge B, Poirier J, Julien D, Gyapay G, Weissenbach J, Hudson TJ, Melan?sson SB, Morgan K. Location score and haplotype analyses of the locus for autosomal recessive spastic ataxia of Charlevoix-Saguenay, in chromosome region 13q11. Am J Hum Genet. 1999 Mar;64(3):768-75. Erratum in: Am J Hum Genet 1999 Apr;64(4):1257.

PubMed ID: 
10053011

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