ophthalmoplegia

Pearson Marrow-Pancreas Syndrome

Clinical Characteristics
Ocular Features: 

Although systemic disease is usually evident during infancy, ocular symptoms such as ptosis and ophthalmoplegia may not be apparent until adulthood in those that survive.  The ocular myopathy in adults can resemble Kearns-Sayre syndrome (530000) as the result of a phenotypic shift from a predominantly hematopoietic disorder to a mitochondrial myopathy.  Bilateral zonular cataracts and strabismus have been reported in a 3 year old male.  A midperiphery pigmentary retinopathy has been observed.  Endothelial cell failure leads to corneal edema. 

Systemic Features: 

Low birth weight, failure to thrive, hypoplastic anemia and exocrine pancreatic dysfunction are often seen in infancy.  Precursor cells in the marrow show typical vacuolization. Malabsorption and insulin-dependent diabetes often develop.  The pancreas and bone marrow may become fibrotic.  Patients with the classic syndrome as a child can develop features of the Kearns-Sayre syndrome if they survive childhood.  Progressive muscle weakness in pharyngeal, facial, neck, and limb muscles is sometimes seen in older individuals and muscle biopsy reveals ragged-red fibers characteristic of mitochondrial disease.  Some patients have an organic aciduria and others develop hepatic failure with elevated transaminase, bilirubin and lipid levels.  Kidney damage results in Fanconi syndrome.  Young children may recover from the refractory anemia eventually but metabolic acidosis with life-threatening lactic acidosis is a constant threat and responsible for many childhood deaths.

Genetics

Deletions in mtDNA involving numerous genes are responsible for this condition.  As a result, it is maternally transmitted but somewhat inconsistently due to mitochondrial heteroplasmy.  Both sexes are affected.  The irregular size of the mtDNA deletions and the tissue distribution of affected mitochondria results in considerable variation in clinical expression.  Defective oxidative phosphorylation seems to be the underlying cause of many of the signs and symptoms.

Treatment
Treatment Options: 

This multisystem disease requires careful monitoring throughout life.  Blood transfusions may be required and careful attention needs to be given to nutrition and metabolic dysfunction.  A few patients have required insulin.  In spite of vigorous treatment of electrolyte imbalances, correction of acidosis, and hormonal supplements, many patients do not survive beyond childhood.  Organ failure requires individualized treatment.

References
Article Title: 

Pearson Syndrome

Farruggia P, Di Marco F, Dufour C. Pearson Syndrome. Expert Rev Hematol. 2018 Jan 16. doi: 10.1080/17474086.2018.1426454. [Epub ahead of print].

PubMed ID: 
29337599

MELAS Syndrome

Clinical Characteristics
Ocular Features: 

This progressive mitochondrial disorder primarily affects muscles and the CNS, including the visual system.  The pattern of ocular deficits is not consistent and those that are present are not specific, requiring the clinician to take the entire neurological picture into consideration.  Hemianopsia, cortical blindness and ophthalmoplegia may be present.  The ERG can show reduced b-wave amplitudes and VEPs may be absent.  The optic nerve head has been described as normal without the atrophy often seen with other mitochondrial disorders.  A pigmentary retinopathy may be present.

Systemic Features: 

The clinical picture is highly variable.  Most commonly patients have myopathy, encephalopathy, lactic acidosis, and stroke-like episodes.  The onset of symptoms is usually in the first two decades of life, most commonly consisting of headaches of sudden onset accompanied by vomiting and seizures.  The headaches may simulate migraines.  Weakness, lethargy, and apathy may be present early.  However, infants and young children may present with failure to thrive, developmental delay, and learning disabilities.  Neurosensory deafness is often seen and peripheral neuropathy is usually evident.  MRIs may show cerebellar hypoplasia and infarctions in the cerebral hemispheres.  Some patients have calcifications in the basal ganglia.  Patients may develop lactic acidosis.  Muscle biopsies often show ragged, red fibers.  The heart is commonly involved with both structural and rhythm defects.  Depending upon the degree and location of brain damage, patients may have hemiparesis, lethargy, ataxia, myoclonic jerks, cognitive decline, and dementia.  Morbidity and mortality are high.

Genetics

MELAS syndrome is a group of disorders caused by mutations in mitochondrial genes (at least 9 have been identified) that alter transfer RNA molecules resulting in disruption of intramitochondrial synthesis of proteins involved in oxidative phosphorylation pathways.  It is both clinically and genetically heterogeneous.  One can expect that any familial occurrence would result from maternal transmission but the occurrence of heteroplasmy results in considerable variability in the severity of clinical disease.

Treatment
Treatment Options: 

There is no effective treatment that prevents development of disease or that slows its progress.

References
Article Title: 

Fibrosis of Extraocular Muscles, CFEOM1

Clinical Characteristics
Ocular Features: 

Hereditary CFEOM is a congenital, nonprogressive condition.  The eyes are usually fixed in the infraducted position about 20-30 degrees below the primary position.  Horizontal movement is absent or severely restricted.  Blepharoptosis is almost always present and patients exhibit a marked chin-up position of gaze.  Binocularity is usually absent.  Some patients have large amounts of astigmatism.  Amblyopia has been reported to occur on a refractive or strabismic basis.  However, careful examination of the optic nerve may reveal anomalies such as increased cupping, asymmetric cupping and hypoplasia and could be responsible for the reduced vision in some patients.

Neuropathologic studies in rare patients have shown defects in brainstem neural development including in one case absence of the superior division of the oculomotor nerve.  Fibrosis of extraocular muscles and Tenon's capsule as well as adhesions to the globe and between muscles have been described.   Anomalous insertions of EOMs may also occur.  An MRI can reveal atrophy of the levator palpebrae and the superior rectus muscles as well as absence or hypoplasia of the oculomotor and sometimes abducens nerves.  It is now considered that CFEOM disorders result from primary neuronal disease resulting in secondary myopathy. 

Systemic Features: 

Late onset gait abnormalities associated with MRI documented vermis atrophy have been reported in a single autosomal dominant pedigree.  The diagnosis of CFEOM1 was confirmed with molecular studies but only two older individuals aged 79 and 53 years had the cerebellar atrophy while a 33 year old in the same family had only CFEOM with no gait difficulties and no neuroimaging abnormalities.

Genetics

CFEOM1 is an autosomal dominant disorder caused by mutations in the KIF21A gene located at 12q12.  This is considered the classic form of congenital, restrictive strabismus but other types such as CFEOM2 (602078) and CFEOM3 (600638, 609384) have also been reported.  CFEOM3 is a clinically heterogeneous autosomal dominant condition and the label is usually applied to individuals who do not meet the criteria for the other two types.  A rare subtype (CFEOM3B) is also due to mutations in the KIF21A gene.  CFEOM3A (600638) is caused by mutations in the TUBB3 gene (16q24) while CFEOM3C (609384) maps to 13q.

The CFEOM2 (602078) phenotype is due to mutations in the PHOX2A (ARIX) gene and inherited in an autosomal recessive pattern.

Other nonsyndromal forms of congenital fibrosis of extraocular muscles include: CFEOM3C (609384), CFEOM5 (616219), and CFEOM with synergistic divergence (609612).  See also Tukel CFEOM syndrome (609428).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Normal ocular movements cannot be restored but large recessions of the inferior recti followed by frontalis suspension of the upper eyelids can improve severe ptosis and the compensatory chin-up gaze. Corneal lubrication must be maintained.  Refractive errors and amblyopia should be corrected.  

References
Article Title: 

Fibrosis of Extraocular Muscles, CFEOM2

Clinical Characteristics
Ocular Features: 

This is a congenital, autosomal recessive, nonprogressive type of CFEOM which has been described in several consanguineous Middle Eastern families.  The responsible mutations are in a different gene than the one responsible for autosomal dominant CFEOM1 cases although some of the clinical features are similar.  However, in CFEOM2 the eyes are less likely to be infraducted and instead are often fixed in extreme abduction.  In addition, the phenotype is more variable with some eyes fixed in the 'neutral' position and others having more mobility than usually seen in CFEOM1 but the clinical heterogeneity is less than that seen in CFEOM3.  Ptosis is part of both phenotypes.  All patients have severe restrictions in ocular motility.  It has been suggested that CEFOM2 patients are likely to have involvement of both superior and inferior divisions of the oculomotor nerve whereas only the superior division is abnormal in CFEOM1.  Binocular vision is absent and amblyopia is common.  The pupils may be small and respond poorly to light. Refractive errors are common.

Based on visual field testing and ERG findings, it has been suggested that subnormal vision in CFEOM2 may be due to undescribed retinal dysfunction.  

Systemic Features: 

Mild facial muscle weakness may be apparent. 

Genetics

This is an autosomal recessive disorder caused by homozygous mutations in the PHOX2A gene at 11q13.3-q13.4.  Another more common form of CFEOM is the autosomal dominant CFEOM1 type (135700) in which the primary fixed deviation is infraduction. The third type is CFEOM3 (600638, 609384) which is clinically more heterogeneous. 

Other nonsyndromal forms of congenital fibrosis of extraocular muscles include: CFEOM3C (609384), CFEOM5 (616219), and CFEOM with synergistic divergence (609612).  See also Tukel CFEOM syndrome (609428).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Restoration of normal ocular motility is difficult but cosmetic improvement is possible by correcting some of the ptosis with frontalis slings.  Corneal lubrication must be maintained and amblyopia should be treated. 

References
Article Title: 

Oculopharyngodistal Myopathy

Clinical Characteristics
Ocular Features: 

Progressive ptosis, which may be asymmetric, is an early sign.  Extraocular palsy occurs as well. 

Systemic Features: 

The mean age of onset of this progressive disease is 22 years.  Pharyngeal and distal limb muscles seem to be primarily involved.  Weakness in masseter, facial, and bulbar muscles have been observed but no muscle group seems to be spared.  Atrophy of facial muscles is common and may be pronounced.  There is considerable variability in expression, particularly in the degree of limb weakness which often appears by the fifth decade.  Swallowing difficulties can be severe.  Respiratory weakness may be evident relatively early, even while patients are still ambulatory.  Loss of ambulation most commonly occurs by the third or fourth decade after the onset of first symptoms.  Serum creatine kinase levels are mildly elevated and histologic changes show chronic myopathic changes with rimmed vacuole formation.  No changes have been found in the central or peripheral nervous system. 

Genetics

The causative mutation has not been identified but mutations causing other forms of hereditary myopathy have been ruled out.  Most families are consistent with autosomal dominant inheritance but the pattern in at least one family has suggested a recessive pattern indicating genetic heterogeneity. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Supportive treatment such as physical and respiratory therapies may be helpful but no specific treatment is available for the muscle disease.

References
Article Title: 

Oculopharyngodistal myopathy

Satoyoshi E, Kinoshita M. Oculopharyngodistal myopathy. Arch Neurol. 1977 Feb;34(2):89-92.

PubMed ID: 
836191

Spinocerebellar Ataxia 7

Clinical Characteristics
Ocular Features: 

Pigmentary changes in the retina are somewhat variable but often begin with a granular appearance in the macula and spread into the periphery.  The macula often becomes atrophic and dyschromatopsia is common.   Retinal thinning is evident, especially in the macula.  Decreased visual acuity and loss of color vision are early symptoms and the ERG shows abnormalities of both rod and cone function.  External ophthalmoplegia without ptosis is a frequent sign.  Most adults and some children eventually are blind. 

Systemic Features: 

Symptoms of developmental delay and failure to thrive may appear in the first year of life followed by loss of motor milestones.  Dysarthria and ataxia are nearly universal features while pyramidal and extrapyramidal signs are more variable.  This can be a rapidly progressive disease and children who develop symptoms by 14 months are often deceased before two years of age.  However, adults with mild disease can survive into the 5th and 6th decades.  Peripheral neuropathy with sensory loss and motor deficits are usually present to some degree but the range of clinical disease is wide.  Cognitive decline and some degree of dementia occur sometimes. 

Genetics

Spinocerebellar ataxia 7 is caused by expanded trinucleotide repeats (CAG) in the ATXN7 gene (3p21.1-p12) and inherited in an autosomal dominant pattern.  The number of repeats is variable and correlated with severity of disease.  Most patients with 36 or more repeats have significant disease. This disorder is sometimes classified as a progressive cone-rod dystrophy.  It is sometimes referred to as olivopontocerebellar atrophy type III or OPCA3.

This disorder exhibits genetic anticipation especially with paternal transmission as succeeding generations often have earlier onset with more severe and more rapidly progressive disease. This is explained by the fact that younger generations tend to have a larger number of repeats and sometimes the diagnosis is made in children before the disease appears in parents or grandparents.

Spinocerebellar ataxia 1 (164400) is a similar autosomal dominant disorder with many of the same clinical and genetic features.  It is caused by excess CAG repeats on the ATXN1 gene on chromosome 6. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No effective treatment is known for the disease.  Low vision aids and mobility training may be useful in early stages. 

References
Article Title: 

Oculopharyngeal Muscular Dystrophy

Clinical Characteristics
Ocular Features: 

Progressive ptosis is the cardinal ocular feature of this syndrome (present in at least 88% of patients).  External ophthalmoparesis of some degree is often present with weakness of upgaze most common.

Systemic Features: 

This is a late onset form of progressive muscular dystrophy with onset of symptoms during midlife (mean age of onset ~48 years).  Evidence of pharyngeal muscle weakness often occurs concomitantly with the ocular signs (43%).  Ptosis occurs first in 43% and dysphagia first in 14%.    Dysarthria and dysphagia are often associated with facial muscle weakness.  Swallowing times for ice cold water and dry food is usually prolonged.  Evidence of weakness and wasting of neck and limb muscles is usually noted later.  Life expectancy is normal in contrast to some other forms of muscular dystrophy.  Some patients have significant gait problems and generalized disability as a result of muscle weakness.

Microscopic studies of muscle biopsies usually show evidence of myopathy with abnormal fibers and accumulations of sarcoplasmic matter.  Intranuclear inclusions consisting of tubular filaments and mitochondrial abnormalities have also been described.  Serum CK can be significantly elevated in severe cases.  

Genetics

This is an autosomal dominant disorder resulting from mutations in the PABPN1 gene located at 14q11.2-q13. Several patients with homozygous and compound heterozygous mutations have also been reported.  The PABPN1 gene product is normally a facilitator of polyadenylation of mRNA molecules and may also be active in regulating mRNA production.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Blepharoplasty may be helpful in cases with severe ptosis.  Cricopharyngeal myotomy for dysphagia and recurrent pneumonia can alleviate symptoms in severe cases although recurrence has been noted after many years.

References
Article Title: 

Myotonic Dystrophy 1

Clinical Characteristics
Ocular Features: 

Posterior subcapsular cataracts may be seen at any age, often with striking iridescent opacities in the overlying cortex as well.  These polychromatic lens changes can be diagnostic but are present in only 50% of young adults with myotonic dystrophy.  When present, they are almost always bilateral.  Proximal muscle involvement leads to ptosis, strabismus, weakness of the orbicularis oculi, and sometimes ophthalmoplegia.  Such muscle weakness may lead to exposure keratitis. 

As many as 25% of patients with DM have a pigmentary retinopathy, usually in a butterfly pattern.

A low IOP and even hypotony is sometimes seen.  The mean IOP in a series of 51 patients has been reported as 10.9 compared with 15.4 in controls.  Using ultrasound biomicroscopy, ciliary body detachments were found in at least one quadrant of all eyes.

Systemic Features: 

In the congenital form, hypotonia, generalized weakness, mental retardation and respiratory insufficiency are often present.  There is a great deal of clinical heterogeneity among patients.  Those with mild disease may have only cataracts and mild myotonia with a normal life expectancy.  Those with more severe disease (classical myotonic dystrophy) have these signs plus marked muscle weakness and wasting.  Cardiac conduction defects with secondary arryhthmias are a significant cause of mortality. Such patients tend to become disabled in adulthood.  Symptoms become evident in the second decade or later.  Deep muscle pain is common and can be severe.  Distal muscle weakness usually begins before facial muscle weakness is apparent.  Myotonia often involves the tongue while proximal muscle weakness can cause dysphagia and dysarthria.  Such patients may also suffer respiratory distress. Reproductive fitness is reduced in males who can have gonadal atrophy.  Frontal balding is common.  Some age-related cognitive decline occurs.

Over 60% of patients have a hearing impairment and more than half of these have auditory brainstem response abnormalities.  Vestibular hypesthesia is present in 37.5%.

Genetics

Myotonic dystrophy 1 is an autosomal dominant disorder caused by a trinucleotide (CTG) repeat expansion in a region of the DMPK gene (19q13.2-q13.3).  The number of repeats varies widely and is roughly correlated with severity of disease.  Infants with congenital myotonia usually have the highest number of repeats and have the most severe cognitive deficits.  The number can expand during gametogenesis each generation (resulting in the phenomenon of anticipation) and females generally transmit larger numbers.  Most infants with congenital myotonia are offspring of affected mothers.  Reduced fetal movement and hydramnios are often noted during such pregnancies.

Affected males have few offspring secondary to gonadal atrophy.  Affected heterozygous females, however, do not have the expected ratio of affected offspring because of the dynamic nature of the number of repeats.  The risk of an affected offspring for a nulliparous afflicted female is only 3-9% and she has a 20-40% risk of recurrence after the birth of an affected child.

In a study of sibships with myotonic dystrophy, 58% of offspring were affected when the transmitting parent was male and 63% when the transmitting parent was female.

At least some of the variable transmission risks and clinical heterogeneity may be explained by somatic instability of the CTG repeat numbers.  The degree of instability, moreover, may also be heritable.  Age of onset, for example, is modified by the level of somatic instability.  Further, patients in whom the repeat expands more rapidly develop symptoms earlier. 

A similar disorder, myotonic dystrophy 2 (602668), is caused by a tetranucleotide repeat expansion in the CNBP gene.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

A variety of pharmaceutical agents have been tried for pain management without consistent results.  No treatment improves the muscle weakness.  Cholesterol lowering drugs such as statins should be avoided.  Physical therapy may be helpful.

Cardiac conduction and structural defects are a significant threat even in asymtomatic patients and require constant monitoring for the development of arrythmias.

References
Article Title: 

Inner ear dysfunction in myotonic dystrophy type 1

Balatsouras DG, Felekis D, Panas M, Xenellis J, Koutsis G, Kladi A, Korres SG. Inner ear dysfunction in myotonic dystrophy type 1. Acta Neurol Scand. 2012 Nov 5. doi: 10.1111/ane.12020. [Epub ahead of print].

PubMed ID: 
23121018

Somatic instability of the expanded CTG triplet repeat in myotonic dystrophy type 1 is a heritable quantitative trait and modifier of disease severity

les F, Couto JM, Higham CF, Hogg G, Cuenca P, Braida C, Wilson RH, Adam B, Del Valle G, Brian R, Sittenfeld M, Ashizawa T, Wilcox A, Wilcox DE, Monckton DG. Somatic instability of the expanded CTG triplet repeat in myotonic dystrophy type 1 is a heritable quantitative trait and modifier of disease severity. Hum Mol Genet. 2012 May 16. [Epub ahead of print].

PubMed ID: 
22595968

Incidence and predictors of sudden death, major conduction defects and sustained ventricular tachyarrhythmias in 1388 patients with myotonic dystrophy type 1

Wahbi K, Babuty D, Probst V, Wissocque L, Labombarda F, Porcher R, Becane HM, Lazarus A, Behin A, Laforet P, Stojkovic T, Clementy N, Dussauge AP, Gourraud JB, Pereon Y, Lacour A, Chapon F, Milliez P, Klug D, Eymard B, Duboc D. Incidence and predictors of sudden death, major conduction defects and sustained ventricular tachyarrhythmias in 1388 patients with myotonic dystrophy type 1. Eur Heart J. 2016 Dec 9. pii: ehw569. [Epub ahead of print] PubMed.

PubMed ID: 
27941019

Optic Atrophy 1

Clinical Characteristics
Ocular Features: 

This form of bilateral optic atrophy may have its onset in early childhood with optic disc pallor, loss of acuity, loss of color vision, and centrocecal scotomas.  However, it is often not manifest until the second decade of life.  Moderate to severe temporal or diffuse pallor can be seen.  The optic disc has been described as normal in 29% of documented carriers and 20% have no visual field defect.  Pallor of the complete disc is found in only 10%.  Consequently, the phenotype is variable, with some individuals having minimal symptoms while others have severe vision loss.  The disease is progressive in some but not all families.  The median visual acutity is 20/70 but ranges from normal to hand motions.  

Histologic studies show atrophy of ganglion cells in the retina and loss of myelin sheaths in the optic nerve.   VEPs are absent or subnormal.  Optical coherence tomography reveals a significant reduction in retinal nerve fiber layer and ganglion cell layer thickness, most marked in the temporal quadrants.

Systemic Features: 

OPA1 is generally not associated with systemic disease.  However, some have sensorineural deafness, ataxia, ptosis, and ophthalmoplegia.  Families with both early and late onset have been reported.  Some (~20%) individuals have a myopathy as well.

Genetics

This is an autosomal dominant disorder resulting from mutations in a nuclear gene, OPA1 (3q28-q29).  The gene product is attached to the mitochondrial cristae of the inner membrane and metabolic studies have implicated the oxidative phosphorylation pathway which seems to be defective with reduced efficiency of ATP synthesis.  Penetrance approaches 90% but this is, of course, age dependent to some extent.

An allelic disorder (125250) is associated with sensorineural deafness, ataxia, and ophthalmoplegia but its uniqueness remains to be established since the same mutations in OPA1 have been found in both conditions.

Other autosomal dominant optic atrophy disorders include OPA5 (610708) and OPA4 (605293).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No effective treatment is available.

References
Article Title: 

OPA1 in multiple mitochondrial DNA deletion disorders

Stewart JD, Hudson G, Yu-Wai-Man P, Blakeley EL, He L, Horvath R, Maddison P, Wright A, Griffiths PG, Turnbull DM, Taylor RW, Chinnery PF. OPA1 in multiple mitochondrial DNA deletion disorders. Neurology. 2008 Nov 25;71(22):1829-31.

PubMed ID: 
19029523

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