hypotonia

Tenorio Syndrome

Clinical Characteristics
Ocular Features: 

The eyebrows appear bushy.  Inflammation of the limbus and keratoconjunctivitis sicca are often present and reported to resemble Sjogren syndrome.

Systemic Features: 

Infants appear large at birth with a large forehead and macrocephaly.  Birth weight, length, and head circumference are usually above the 97th percentile. The mandible appears large and the lips are full and ‘fleshy’.  Dentition is delayed.  Recurrent stomatitis and gastroesophageal reflux have been noted.  Closure of the fontanels is delayed.  Hypotonia and hyperflexible joints can be a feature.

Multiple brain anomalies have been described including cortical atrophy, dilated and asymmetrical ventricles, and mild hydrocephalus.  Psychomotor development and milestones are delayed.  Intellectual disabilities, syncope, hypoglycemia, seizures, apneic episodes, mood anomalies, abnormal gait, and general clumsiness may be present.  There was considerable clinical variation among the six reported patients. 

Genetics

Heterozygous mutations in RNF125 (18q12.1) are responsible for this syndrome. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

A new overgrowth syndrome is due to mutations in RNF125

Tenorio J, Mansilla A, Valencia M, Martinez-Glez V, Romanelli V, Arias P, Castrejon N, Poletta F, Guillen-Navarro E, Gordo G, Mansilla E, Garcia-Santiago F, Gonzalez-Casado I, Vallespin E, Palomares M, Mori MA, Santos-Simarro F, Garcia-Minaur S, Fernandez L, Mena R, Benito-Sanz S, del Pozo A, Silla JC, Ibanez K, Lopez-Granados E, Martin-Trujillo A, Montaner D; SOGRI Consortium, Heath KE, Campos-Barros A, Dopazo J, Nevado J, Monk D, Ruiz-Perez VL, Lapunzina P. A new overgrowth syndrome is due to mutations in RNF125. Hum Mutat. 2014 Dec;35(12):1436-41.

PubMed ID: 
25196541

Mitochondrial Short-Chain Enoyl-CoA Hydratase 1 Deficiency

Clinical Characteristics
Ocular Features: 

The ocular phenotype has not been thoroughly studied.  Nystagmus has been reported in several infants.

Systemic Features: 

Evidence of severe psychomotor retardation is evident at birth or shortly thereafter.  Neonatal hypotonia with a poor suck reflex and episodic apnea is evident.  Spasticity may become evident later.  Brain imaging shows T-weighted hyperintensity areas in the basal ganglia resembling Leigh syndrome lesions.  The corpus callosum appears thin.  Serum and CSF lactate is elevated and decreased activity of the pyruvate dehydrogenase complex is present.

Infants do not achieve normal developmental milestones such as speech or sitting unsupported and several have died early in childhood from cardiorespiratory failure, possibly related to a combined mitochondrial respiratory chain dysfunction.

Genetics

The transmission pattern in several families is consistent with autosomal recessive inheritance.  Compound heterozygous mutations have been found in the ECHS1 gene (10q26.3).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

CODAS Syndrome

Clinical Characteristics
Ocular Features: 

Dense nuclear cataracts can be seen by six months of age.  Some patients have ptosis. The fundi have been described as normal at one month of age in a single infant but vision was described at the 20/200 level at 2 years of age.  Cataracts noted at 4 months had been removed.

Systemic Features: 

Patients have multiple severe systemic abnormalities.  There is generalized developmental delay along with mild microcephaly and hypotonia.   The forehead is often broad while the face appears flattened with anteverted nares, a flat nasal bridge, a short philtrum, low-set and crumpled ears.  Infants may have an inadequate upper respiratory apparatus with atrophic vocal cords and some die of laryngeal obstruction in the first days of life.  Sialorrhea and difficulty swallowing have been noted.  Mild to moderate neurosensory hearing loss is often present but there may also be a conduction component to this. 

Brain imaging has revealed large ventricles, with subcortical hypomyelination, a thin corpus callosum, and prominent cortical sulci.  The vertebrae may have coronal clefts and scoliosis often develops. Generalized metaphyseal dysplasia and delayed bone age are usually present.  The anus may be imperforate and a rectovaginal fistula and cryptorchidism have been reported.  Long bones may be malformed as well and most patients are short in stature. Delayed dentition, enamel dysplasia, and abnormal cusp morphology are often present.  Cardiac septal defects may be seen.

Genetics

Homozygous mutations in LONF1 (19p13.3) segregate with the phenotype.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no general treatment available and infants sometimes die from laryngeal obstruction in the first days of life.   Individual anomalies may be surgically correctable in selected individuals.  Occasional infants are stillborn but one patient died an accidental death at 14 years of age. 

References
Article Title: 

CODAS syndrome is associated with mutations of LONP1, encoding mitochondrial AAA+ Lon protease

Strauss KA, Jinks RN, Puffenberger EG, Venkatesh S, Singh K, Cheng I, Mikita N, Thilagavathi J, Lee J, Sarafianos S, Benkert A, Koehler A, Zhu A, Trovillion V, McGlincy M, Morlet T, Deardorff M, Innes AM, Prasad C, Chudley AE, Lee IN, Suzuki CK. CODAS syndrome is associated with mutations of LONP1, encoding mitochondrial AAA+ Lon protease. Am J Hum Genet. 2015 Jan 8;96(1):121-35.

PubMed ID: 
25574826

Spinocerebellar Ataxia 18

Clinical Characteristics
Ocular Features: 

Ocular signs in SCAR18 include nystagmus, oculomotor apraxia, and optic atrophy.  The nystagmus may be rotatory or horizontal and can be gaze-evoked.  Some patients have intermittent and tonic upgaze.  Visual acuity has not been reported.

Systemic Features: 

Patients are developmentally delayed and have intellectual disability.  These features do not seem to be progressive.  Ataxia, both truncal and cerebellar, is present.  Mobility is impaired from early childhood and eventually requires assistance.   Joint contractures sometimes develop and patients can be wheelchair-bound by the second decade.  Dysarthric speech is common.  No dysmorphic facial features are present.

Brain imaging shows progressive cerebellar and sometimes cerebral atrophy.

Genetics

This autosomal recessive disorder results from homozygous deletions in the GRID2 gene (4q22).  This gene codes for a subunit of the glutamate receptor channel and is thought to be selectively expressed in the Purkinje cells of the cerebellum.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.  However, physical therapy, assistive devices for mobility, and low vision aids may be helpful.

References
Article Title: 

Galloway-Mowat Syndrome

Clinical Characteristics
Ocular Features: 

Microphthalmia, hypertelorism, epicanthal folds and ptosis are prominent ocular features.  Other manifestations include corneal opacities, cataracts, and optic atrophy.  Nystagmus of a roving nature is seen in all individuals and is usually present at birth.  There is evidence of visual impairment in more than 90% of individuals.  Features of an anterior chamber dysgenesis such as a hypoplastic iris are sometimes present.

The ocular features of this syndrome have not been fully described.

Systemic Features: 

Infants are born with low birth weight due to intrauterine growth retardation and there is often a history of oligohydramnios.  Newborns are often floppy and hypotonic although spasticity may develop later.  A small midface and microcephaly (80%) with a sloping forehead and a flat occiput are frequently evident.  The ears are large, floppy, and low-set while the hard palate is highly arched and the degree of micrognathia can be severe.  The fists are often clenched and the digits can appear narrow and arachnodactylous.  Hiatal hernias may be present.

Many patients develop features of the nephrotic syndrome in the first year of life with proteinuria and hypoalbuminemia due to glomerular kidney disease and renal system malformations.  Renal biopsies show focal segmental glomerulosclerosis in the majority of glomeruli.

Evidence of abnormal neuronal migration with brain deformities such as cystic changes, porencephaly, encephalomalacia, and spinal canal anomalies have been reported.  MRI imaging shows diffuse cortical and cerebellar atrophy atrophic optic nerves, and thinning of the corpus callosum.  The normal striated layers of the lateral geniculate nuclei are obliterated.  The cerebellum shows severe cellular disorganization with profound depletion of granule cells and excessive Bergmann gliosis.  The vermis is shortened. 

Multifocal seizures are sometimes (40%) seen in infancy and early childhood and the EEG generally shows slowed and disorganized backgound and sometimes a high-voltage hypsarrhythmia.  The degree of psychomotor delay and intellectual disability is often severe.   Most patients are unable to sit independently (90%), ambulate (90%), or make purposeful hand movements (77%).  The majority (87%) of children have extrapyramidal movements and a combination of axial dystonia and limb chorea.  Mean age of death is about 11 years (2.7 to 28 years in one series) and most die from renal failure.

Genetics

Gallaway-Mowat syndrome is likely a spectrum of disease.  Homozygous mutations in the WDR73 gene (15q25) are responsible for one form of this syndrome.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for GAMOS.

References
Article Title: 

Recessive nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum is caused by homozygous protein-truncating mutations of WDR73

Jinks RN, Puffenberger EG, Baple E, Harding B, Crino P, Fogo AB, Wenger O, Xin B, Koehler AE, McGlincy MH, Provencher MM, Smith JD, Tran L, Al Turki S, Chioza BA, Cross H, Harlalka GV, Hurles ME, Maroofian R, Heaps AD, Morton MC, Stempak L, Hildebrandt F, Sadowski CE, Zaritsky J, Campellone K, Morton DH, Wang H, Crosby A, Strauss KA. Recessive nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum is caused by homozygous protein-truncating mutations of WDR73. Brain. 2015 Aug;138(Pt 8):2173-90.  PubMed PMID: 26070982.

PubMed ID: 
26070982

Loss-of-Function Mutations in WDR73 Are Responsible for Microcephaly and Steroid-Resistant Nephrotic Syndrome: Galloway-Mowat Syndrome

Colin E, Huynh Cong E, Mollet G, Guichet A, Gribouval O, Arrondel C, Boyer O, Daniel L, Gubler MC, Ekinci Z, Tsimaratos M, Chabrol B, Boddaert N, Verloes A, Chevrollier A, Gueguen N, Desquiret-Dumas V, Ferre M, Procaccio V, Richard L, Funalot B, Moncla A, Bonneau D, Antignac C. Loss-of-Function Mutations in WDR73 Are Responsible for Microcephaly and Steroid-Resistant Nephrotic Syndrome: Galloway-Mowat Syndrome. Am J Hum Genet. 2014 Dec 4;95(6):637-48..

PubMed ID: 
25466283

Optic Atrophy, Areflexia, Ataxia, Hearing Loss

Clinical Characteristics
Ocular Features: 

Progressive optic atrophy is a consistent feature of all reported cases.  It may have its onset during the first year or two of life but always before the age of 10 years.  Nystagmus may be seen early during acute febrile episodes but eventually becomes permanent.

Systemic Features: 

Onset of neurological symptoms usually occurs in childhood during or following an acute febrile illness which may be recurrent.  This may consist of cerebellar ataxia, hypotonia, drowsiness, dysarthria, and lethargy.  There may be partial or full recovery following the febrile illness initially but some signs remain after subsequent episodes.  Areflexia and sensorineural deafness can be additional signs and pes cavus eventually appears.

The acute febrile episodes tend to decrease in time along with the progression of neurological signs.  Plantar responses remain normal while peripheral neuropathy and seizures are not consistent features.  MRI imaging of the brain is normal.  Cognitive function usually remains normal but some children have autism features and social adjustment problems have been noted.

Genetics

This is an autosomal dominant condition (which may be considered a form of ‘ataxia-plus’) secondary to heterozygous mutations in the ATP1A3 gene (19q13.31).  The protein product is a subunit of an ATPase enzyme primarily active in neural tissue.

Other mutations in the same gene have been found in dystonia-12 and alternating hemiplegia of childhood.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is known for this condition but physical therapy and mobility-assistive devices may be helpful.  Low vision aids may be useful as well.

References
Article Title: 

A novel recurrent mutation in ATP1A3 causes CAPOS syndrome

Demos MK, van Karnebeek CD, Ross CJ, Adam S, Shen Y, Zhan SH, Shyr C, Horvath G, Suri M, Fryer A, Jones SJ, Friedman JM; FORGE Canada Consortium. A novel recurrent mutation in ATP1A3 causes CAPOS syndrome. Orphanet J Rare Dis. 2014 Jan 28;9:15.

PubMed ID: 
24468074

Microphthalmia, Syndromic 5

Clinical Characteristics
Ocular Features: 

One or both eyes may be small, sometimes resembling clinical anophthalmia. Other ocular anomalies such as coloboma, microcornea, cataracts, and hypoplasia or agenesis of the optic nerve have been reported.

A pigmentary retinopathy has been described.  The retinal vessels are often attenuated and sometimes sparse.  The optic nerves and chiasm are frequently absent or hypoplastic as seen on the MRI.  ERG and VEP responses are inconsistent but are generally abnormal indicating photoreceptor malfunction.  

Systemic Features: 

Patients have a variety of systemic abnormalities including pituitary dysfunction, joint laxity, hypotonia, agenesis of the corpus callosum, and seizures.  Hypothyroidism and deficiencies of growth hormone, gonadotropins, and cortisol are present in some patients.  Developmental delay and cognitive impairment are frequently present but mental functioning is normal in some patients.  The genitalia of males are often underdeveloped.  Patients are often short in stature.

Genetics

This is an autosomal dominant condition secondary to heterozygous mutations in the OTX2 gene (14q22.3).  A variety of point mutations as well as microdeletions involving the OTX2 gene have been reported.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

There is no treatment for the syndrome but surgical and/or endocrinological treatment may be used to correct individual features.  Special education and low vision aids may be helpful in selected patients.

References
Article Title: 

Heterozygous mutations of OTX2 cause severe ocular malformations

Ragge NK, Brown AG, Poloschek CM, Lorenz B, Henderson RA, Clarke MP, Russell-Eggitt I, Fielder A, Gerrelli D, Martinez-Barbera JP, Ruddle P, Hurst J, Collin JR, Salt A, Cooper ST, Thompson PJ, Sisodiya SM, Williamson KA, Fitzpatrick DR, van Heyningen V, Hanson IM. Heterozygous mutations of OTX2 cause severe ocular malformations. Am J Hum Genet. 2005 Jun;76(6):1008-22. Apr 21. Erratum in: Am J Hum Genet. 2005 Aug;77(2):334..

PubMed ID: 
15846561

Orofaciodigital Syndrome, Type VI

Clinical Characteristics
Ocular Features: 

Hypertelorism and epicanthal folds have been described.  Some patients have nystagmus and strabismus. Ocular apraxia and difficulties in smooth visual pursuit may be present.   

Systemic Features: 

Polydactyly of the hands is a common feature.  The central metacarpal is often Y-shaped leading to ‘central polydactyly’.  The large toes may be bifid.  Cognitive deficits are common and some patients have been considered mentally retarded.  The ears are low-set and rotated posteriorly.  Some patients have a conductive hearing loss.  Oral anomalies may include a lobed tongue, lingual and sublingual hemartomas, micrognathia, clefting, and multiple buccoalveolar frenula.  Congenital heart anomalies, micropenis, and cryptorchidism have been reported.  Tachypnea and tachycardia have been noted.  Some patients have some degree of skeletal dysplasia and many individuals are short in stature.

The presence of cerebellar abnormalities such as hypoplasia (including absence) of the vermis may help to distinguish type VI from other forms of OFDS.  Hypothalamic dysfunction may be responsible for poor temperature regulation (hyperthermia). The ‘molar tooth sign’ seen on brain MRIs in Joubert syndrome (213300) is also present in OFDS VI. 

Genetics

This is a rare condition with limited family information.  Parents in one family were consanguineous, and multiple affected sibs in other families suggest this may be an autosomal recessive condition.  Homozygous mutations in TMEM216 have been found. Other patients have mutations in C5orf42.

Many of the clinical features in OFDS VI are also found among individuals with Joubert (213300) and Meckel (249000) syndromes that also sometimes have mutations in the TMEM216 and C5orf42 genes.  Some consider all of these conditions to be members of a group of overlapping disorders called ciliopathies or ciliary dyskinesias.   

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No specific treatment is available for this syndrome but individual signs and symptoms may need treatment.

References
Article Title: 

C5orf42 is the major gene responsible for OFD syndrome type VI

Lopez E, Thauvin-Robinet C, Reversade B, Khartoufi NE, Devisme L, Holder M, Ansart-Franquet H, Avila M, Lacombe D, Kleinfinger P, Kaori I, Takanashi JI, Le Merrer M, Martinovic J, No?'l C, Shboul M, Ho L, G?oven Y, Razavi F, Burglen L, Gigot N, Darmency-Stamboul V, Thevenon J, Aral B, Kayserili H, Huet F, Lyonnet S, Le Caignec C, Franco B, Rivi?(r)re JB, Faivre L, Atti?(c)-Bitach T. C5orf42 is the major gene responsible for OFD syndrome type VI. Hum Genet. 2013 Nov 1. [Epub ahead of print].

PubMed ID: 
24178751

Mutations in TMEM216 perturb ciliogenesis and cause Joubert, Meckel and related syndromes

Valente EM, Logan CV, Mougou-Zerelli S, Lee JH, Silhavy JL, Brancati F, Iannicelli M, Travaglini L, Romani S, Illi B, Adams M, Szymanska K, Mazzotta A, Lee JE, Tolentino JC, Swistun D, Salpietro CD, Fede C, Gabriel S, Russ C, Cibulskis K, Sougnez C, Hildebrandt F, Otto EA, Held S, Diplas BH, Davis EE, Mikula M, Strom CM, Ben-Zeev B, Lev D, Sagie TL, Michelson M, Yaron Y, Krause A, Boltshauser E, Elkhartoufi N, Roume J, Shalev S, Munnich A, Saunier S, Inglehearn C, Saad A, Alkindy A, Thomas S, Vekemans M, Dallapiccola B, Katsanis N, Johnson CA, Atti?(c)-Bitach T, Gleeson JG. Mutations in TMEM216 perturb ciliogenesis and cause Joubert, Meckel and related syndromes. Nat Genet. 2010 Jul;42(7):619-25.

PubMed ID: 
20512146

External Ophthalmoplegia, Facial Weakness, and Malignant Hyperthermia

Clinical Characteristics
Ocular Features: 

A subset of patients with malignant hyperthermia susceptibility (MHS) secondary to mutations in RYR1 has congenital ophthalmoplegia and ptosis.   Magnetic resonance imaging may reveal hypoplasia of extraocular muscles and intraorbital cranial nerves.

Systemic Features: 

The weakness in extraocular and levator muscles is sometimes associated with more generalized myopathy of a variable degree.  The myopathy may be progressive and individuals with extensive skeletal muscle weakness may have respiratory insufficiency and scoliosis. The clinical spectrum is broad and there is no consistent pattern in the degree of skeletal muscle weakness associated with ocular muscle involvement.  This may be explained in part by the variety of myopathies found among patients with mutations in RYR1 such as:  central core disease, multiminicore disease, congenital fiber type disproportion, centronuclear myopathy, and nemaline myopathy.

Malignant hyperthermia due to mutations in RYR1 is most commonly inherited as an autosomal dominant trait precipitated by exposure to certain volatile anesthetic agents such as halothane, isoflurane, and enflurane used in association with succinylcholine during general anesthesia.  Patients may experience acidosis, muscle rigidity, rhabdomyolysis and tachycardia with arrhythmias.  Myoglobinuria may lead to renal failure.

Exercise-induced heat stress rarely precipitates malignant hyperthermia.

Genetics

Ptosis, ophthalmoplegia, and susceptibility to malignant hyperthermia can occur as separate heritable conditions and it is uncommon for them to coexist as in the MHS1 syndrome described here.  Due to the heterogeneous signs of muscle disease reported among and between families, it is likely that MHS1 consists of more than one disorder.  Mutations in RYR1 are commonly associated with susceptibility to malignant hyperthermia while the co-occurrence of skeletal muscle disease is inconsistent and involvement of extraocular muscles is even rarer.

There is good evidence that at least 6 types of MHS exist.  A large number of responsible mutations in 2 genes, RYR1 (19q13.2) and CACNA1S (1q32.1), have been identified and there is good evidence that at least 4 additional loci exist.  Mutations in RYR1 are responsible for MHS1 and account for approximately 70% of susceptible individuals.  Families with both autosomal dominant and autosomal recessive inheritance patterns have been reported.  

It is not understood why some families with MHS1 have ocular and skeletal muscle abnormalities while others do not.  External ophthalmoplegia is most often secondary to mutations in mitochondrial DNA but the importance of presurgical recognition of the risk of malignant hyperthermia suggests that pre-surgery gene screening for RYR1 in such patients is warranted.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

The best treatment is prevention by using alternate anesthetic agents if the risk is recognized preoperatively.  Temperature should be monitored in all patients undergoing general anesthesia since prompt recognition of hyperthermia is essential.  Inhalation agents and succinylcholine must be discontinued and dantrolene sodium should be given promptly.  Metabolic abnormalities must be corrected and both external and internal body cooling should be initiated immediately.  Intravascular coagulation is an additional risk and coagulation profiles should be obtained.

A positive family history of MHS requires pre-anesthesia gene testing but failure to detect a mutation in known genes does not rule out susceptibility.

Ptosis surgery may be helpful in selected patients.

References
Article Title: 

Recessive RYR1 mutations cause unusual congenital myopathy with prominent nuclear internalization and large areas of myofibrillar disorganization

Bevilacqua JA, Monnier N, Bitoun M, Eymard B, Ferreiro A, Monges S, Lubieniecki F, Taratuto AL, Laquerriere A, Claeys KG, Marty I, Fardeau M, Guicheney P, Lunardi J, Romero NB. Recessive RYR1 mutations cause unusual congenital myopathy with prominent nuclear internalization and large areas of myofibrillar disorganization. Neuropathol Appl Neurobiol. 2011 Apr;37(3):271-84.

PubMed ID: 
21062345

Myasthenic Syndromes, Congenital, Including AChR Deficiency

Clinical Characteristics
Ocular Features: 

The congenital myasthenic syndromes are genetically and clinically heterogeneous.  Ptosis is the outstanding ocular sign and virtually always present.  Strabismus and ophthalmoplegia are less common.  These signs are not helpful in the differential diagnosis of the many types of congenital myasthenia.

Some degree of ptosis is usually evident during the first 6 months of life.  By about 2 years of age strabismus and ophthalmoparesis are apparent but this sequence is highly variable.

Systemic Features: 

This is a group of nonprogressive disorders most often associated with acetylcholine receptor (AChR) defects at the neuromuscular junction.  An early sign may be decreased fetal movements.  Generalized weakness, a weak cry, and hypotonia are evident at birth.  Easy fatigability and limb weakness are noted in early childhood and affected children have difficulty running. Facial weakness, dysarthria, weakness of the tongue, and dysphagia are often present and many patients have respiratory difficulties. Motor development can be delayed.  Acute illnesses may exacerbate muscle weakness.

Genetics

This is the most common form of the congenital myasthenic syndromes. It is an autosomal recessive disorder of the postsynaptic type, so called because the mutations occur in genes that encode the subunits of acetylcholine receptors: CHRNE(17P13.2), and CHRNB1(17p13.1).  A similar phenotype results from mutations in MUSK (9p31.3) which is critical for synaptic differentiation.

Mutations in RAPSN(11p11.2), whose protein product is important for stabilization of the acetylcholine receptors at the endplate, may result in a similar phenotype but may also produce the fetal akinesia deformation sequence.  This lethal condition is often associated with severe respiratory disease and dysmorphism including limb contractures, micrognathia, and feeding difficulties.  Nothing is known about the ocular signs.

Another autosomal recessive congenital myasthenic syndrome (610542), CMSTA1, has a somewhat later onset (adolescence) and weakness in a limb girdle distribution but no ptosis or oculomotor problems.  Tubular aggregates of muscle fibers can be seen on biopsy.

Presynaptic autosomal recessive forms of congenital myasthenia such as CMS20 (617143) caused by mutations in SLC5A7 (2q12) and CMS21 (617239) secondary to mutations in SLC18A3 (10q11.23) with severe episodic apnea and ocular signs of ptosis and ophthalmoparesis have been reported.

Other postsynaptic forms of congenital myasthenia are the fast-channel type (FCCNS) (608930) and the slow channel type (SCCMS) (601462).  Ophthalmoparesis occurs early in both types.

The classification of congenital myasthenia syndromes is under construction.  In the case of many types only a single or very few families have been reported.   While the clinical manifestations involve alterations in the neuromuscular junnction, some result from heterozygous mutations while others are due to homozygous changes.  The defect may reside in presynaptic, synaptic, or postsynaptic mechanisms.  For a discussion and comprehensive listing of the various types see 601462.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cholinesterase inhibitor drugs can be highly beneficial in some forms of the disease but genotyping is necessary before attempting pharmacological therapy.  Frequent ventilation and enteric feeding may be helpful for selected individuals.  Individuals should be protected from acute illnesses, especially respiratory infections.

References
Article Title: 

Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea

Bauche S, O'Regan S, Azuma Y, Laffargue F, McMacken G, Sternberg D, Brochier G, Buon C, Bouzidi N, Topf A, Lacene E, Remerand G, Beaufrere AM, Pebrel-Richard C, Thevenon J, El Chehadeh-Djebbar S, Faivre L, Duffourd Y, Ricci F, Mongini T, Fiorillo C, Astrea G, Burloiu CM, Butoianu N, Sandu C, Servais L, Bonne G, Nelson I, Desguerre I, Nougues MC, Boeuf B, Romero N, Laporte J, Boland A, Lechner D, Deleuze JF, Fontaine B, Strochlic L, Lochmuller H, Eymard B, Mayer M, Nicole S. Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea. Am J Hum Genet. 2016 Sep 1;99(3):753-61.

PubMed ID: 
27569547

Congenital myasthenic syndromes

Hanta?O D, Richard P, Koenig J, Eymard B. Congenital myasthenic syndromes. Curr Opin Neurol. 2004 Oct;17(5):539-51. Review.

PubMed ID: 
15367858

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