encephalopathy

Hypotonia, Infantile, with Psychomotor Retardation And Characteristic Facies 2

Clinical Characteristics
Ocular Features: 

Anomalies of periocular structures are part of the characteristic facial morphology.  The lid fissures slant downward and epicanthal folds are with ptosis are generally present.  Strabismus and nystagmus are characteristic features.

Systemic Features: 

This is a severe congenital neurodevelopmental disorder with global delay, hypotonia, and characteristic facies.  It is usually present at birth and soon manifest as a profound intellectual delay.  Most patients do not develop speech or independent motor skills.  Feeding difficulties are evident early and often require gastric tube placement for nutrition.  Failure to thrive is common.   Most patients have seizures of a tonic-clonic or atonic type which may be controlled with medication. 

Microcephaly, brachycephaly, plagiocephaly, and brachycephaly have been described.  A high forehead with frontal bossing, facial hypotonia, triangular facies have been described.  The ears are low-set and posteriorly rotated.  The upper lip is often thin and the mouth is commonly open.  The neck appears short, the nose is bulbous while the nasal bridge is prominent and the nares may be anteverted.

Brain imaging is normal in some patients but there is evidence of generalized cerebral atrophy, with a thin corpus callosum and decreased myelination in others.  Variable features such as scoliosis, hip contractures, muscle wasting, and dyskinesias are sometimes seen.

Genetics

This disorder is caused by homozygous or compound heterozygous mutations in the UNC80 gene (2q34).  

For somewhat similar disorders see IHPRF1 (615419) and IHPRF3 (616900).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Biallelic Mutations in UNC80 Cause Persistent Hypotonia, Encephalopathy, Growth Retardation, and Severe Intellectual Disability

Stray-Pedersen A, Cobben JM, Prescott TE, Lee S, Cang C, Aranda K, Ahmed S, Alders M, Gerstner T, Aslaksen K, Tetreault M, Qin W, Hartley T, Jhangiani SN, Muzny DM, Tarailo-Graovac M, van Karnebeek CD; Care4Rare Canada Consortium; Baylor-Hopkins Center for Mendelian Genomics, Lupski JR, Ren D, Yoon G. Biallelic Mutations in UNC80 Cause Persistent Hypotonia, Encephalopathy, Growth Retardation, and Severe Intellectual Disability. Am J Hum Genet. 2016 Jan 7;98(1):202-9.

PubMed ID: 
26708751

UNC80 mutation causes a syndrome of hypotonia, severe intellectual disability, dyskinesia and dysmorphism, similar to that caused by mutations in its interacting cation channel NALCN

Perez Y, Kadir R, Volodarsky M, Noyman I, Flusser H, Shorer Z, Gradstein L, Birnbaum RY, Birk OS. UNC80 mutation causes a syndrome of hypotonia, severe intellectual disability, dyskinesia and dysmorphism, similar to that caused by mutations in its interacting cation channel NALCN. J Med Genet. 2016 Jun;53(6):397-402.

PubMed ID: 
26545877

Encephalopathy, Progressive, Early-Onset, wtih Brain Atrophy and Spasticity

Clinical Characteristics
Ocular Features: 

Optic atrophy or cortical visual impairment with lack of visual tracking have been described in all patients.

Systemic Features: 

Microcephaly is evident at birth with global developmental delay and hearing loss.  One patient of 3 reported in 2 unrelated families had brief flexion seizures at 5 months.  Developmental regression and stagnation may become evident within the first months of life.  The EEG showed a hypsarrhythmia pattern.  Truncal hypotonia, spasticity, dystonia and/or myoclonus, scoliosis, and dysphagia are also features.  Two of the three reported patients had seizures. 

Brain MRI showed a pattern of pontine hypoplasia, partial agenesis of the corpus callosum, modified frontal gyri and diffuse cortical atrophy with enlarged ventricles have been described.  The cerebellum seems to be spared.

Genetics

Homozygous or compound heterozygous mutations in the TRAPPC12 gene (2p25.3) were found in 3 children in 2 unrelated families with this disorder.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

PEHO-Like Syndrome

Clinical Characteristics
Ocular Features: 

Poor visual fixation and attention has been noted during the first 6 months of life.  Optic atrophy has been described and epicanthal folds may be present.

Systemic Features: 

General hypotonia with developmental delay and progressive microcephaly are evident in the first 6-12 months of life.  Seizures may be present at birth or within the first month of life.  Edema of the feet, hands, and face are also present at birth.  Cognitive deficits and motor delays are usually evident during infancy.  The central hypotonia may be accompanied by peripheral spasticity.  Kyphoscoliosis often develops.  Other dysmorphic features include micrognathia, narrow forehead, short nose, and open mouth.

Brain imaging reveals coarse pachygyria, polymicrogyria, and dilated ventricles with hypoplastic corpus callosum and pons.  Cerebellar hypoplasia was found in one child. 

Genetics

This presumed autosomal recessive disorder is associated with homozygous mutations in the CCDC88A gene (2p16.1).  Three affected children have been reported in a consanguineous family.

A somewhat similar disorder known as PEHO syndrome (260565) results from homozygous mutations in the ZNHIT3 gene. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

The PEHO syndrome

Riikonen R. The PEHO syndrome. Brain Dev. 2001 Nov;23(7):765-9. Review.

PubMed ID: 
11701291

Epileptic Encephalopathy, Early Infantile 47

Clinical Characteristics
Ocular Features: 

The fundus is normal early but optic atrophy with narrowed vessels develops eventually.  Cerebral visual impairment has been described.  VEPs were normal at 4 months of age in one patient.

Systemic Features: 

Tonic seizures have their onset in the first month of life.  These become refractory as documented by the EEG which shows severe background slowing, multifocal origins, and hypsarrhythmia.  Psychomotor development is severely delayed and accompanied by profound intellectual disability.  The two reported children were unable to stand and never developed speech.  Feeding difficulties requires tube feeding.  Microcephaly eventually develops along with axial hypotonia and limb ataxia.

Brain MRI was normal at 5 months of age in one individual but at 6 years old showed cerebellar atrophy.  Her younger male sibling at 2 months of age had a normal MRI but cerebellar atrophy was present at 3 years of age.  He died at 3.5 years while his older sib died at age 7 years.

Genetics

Heterozygous mutations in the FGF12 gene (3q28-q29) are responsible for this condition.  One family with 2 affected children has been reported but neither parent carried the mutation in somatic cells suggesting germline mosaicism.

For autosomal recessive forms of early onset epileptic encephalopathy in this database see Epileptic Encephalopathy, Early Infantile 28 (616211) and Epileptic Encephalopathy, Early Infantile 48 (617276).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is available for the general condition.  Complete supportive care is required.  Seizures are described as 'refractory' to treatment.

References
Article Title: 

Mitochondrial DNA Depletion Syndrome 3

Clinical Characteristics
Ocular Features: 

Nystagmus, disconjugate eye movements, and "optic dysplasia" have been noted.

Systemic Features: 

Infants feed poorly which is frequently associated with vomiting, failure to thrive, and growth delay.  They are hypothermic, hypoglycemic, and often jaundiced with signs of liver failure noted between birth and 6 months of age and death by approximately 1 year of age.  Hepatosplenomegaly is present early with abnormal liver enzymes, cholestasis, steatosis, and hepatocellular loss followed by cirrhosis with portal hypertension.  Metabolic acidosis, hyperbilirubinemia, hypoalbuminemia, and hypoglycemia are often present.  Mitochondrial DNA depletion in the liver approaches 84-90%.

All patients have encephalopathic signs with evidence of cerebral atrophy, microcephaly, hypotonia.  Hyperreflexia may be present and some infants have seizures.  Muscle tissue, however, has normal histology and respiratory chain activity.

Genetics

This disorder results from homozygous or compound heterozygous mutations in the DGUOK gene (2p13).

The same gene is mutated in PEOB4 (617070).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no effective treatment.  Liver transplantation in one infant was unsuccessful.  

References
Article Title: 

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

Congenital Disorder of Glycosylation, Type Ia

Clinical Characteristics
Ocular Features: 

Strabismus, roving eye movements (and nystagmus), and visual inattention are found in nearly all patients. Esotropia with defective abduction seems to be the most common oculomotor finding and may be present at birth.  Cataracts, ocular colobomas, oculomotor apraxia, disc pallor, and glaucoma have also been reported.  Vision is always subnormal. Reports of ocular disease before modern genotyping are not specific to the subtypes of CDG I now recognized.

This is a congenital, progressive disorder of photoreceptor degeneration with a later onset of progressive pigmentary retinopathy.  It is described in some cases as a typical retinitis pigmentosa.  The ERG is abnormal in all patients even if the pigmentary pattern is atypical for RP.  Rod responses are usually absent while the cone b-wave implicit time is delayed.  The degree of photoreceptor damage is variable, however.  Extended retinal function among younger patients suggest that the ‘on-pathway’ evolving synapses in the outer plexiform layer among photoreceptors, bipolar cells, and horizontal cells is severely dysfunctional.

Systemic Features: 

This is a multisystem disorder, often diagnosed in the neonatal period by the presence of severe encephalopathy with hypotonia, hyporeflexia, and poor feeding.  Failure to thrive, marked psychomotor retardation, delayed development, growth retardation, and ataxia become evident later in those who survive.  Cerebellar and brainstem atrophy with a peripheral neuropathy can be demonstrated during late childhood.  Some older patients have a milder disease, often with muscle atrophy and skeletal deformities such as kyphoscoliosis and a fusiform appearance of the digits.  Maldistribution of subcutaneous tissue is often seen resulting in some dysmorphism, especially of the face.  Hypogonadism and enlargement of the labia majora are commonly present.  Some patients have evidence of hepatic and cardiac dysfunction which together with severe infections are responsible for a 20% mortality rate in the first year of life.

Genetics

This is one of a group of genetically (and clinically) heterogeneous autosomal recessive conditions caused by gene mutations that result in enzymatic defects in the synthesis and processing of oligosaccharides onto glycoproteins. This type (Ia) is the most common.   The mutation lies in the PMM2 gene (16p13.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Most children require tube feeding with nutritional supplements.  The risk of systemic infections is high.  Those patients who survive into the second decade and beyond may require orthopedic procedures and are confined to wheelchairs.  Physical, occupational, and speech therapy along with parental support are important.

References
Article Title: 

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: 
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