intellectual disability

Neurodevelopmental Disorder, Mitochondrial, with Abnormal Movements and Lactic Acidosis

Clinical Characteristics
Ocular Features: 

Optic atrophy is sometimes present.  Nystagmus, and strabismus are seen in some patients.  A pigmentary retinopathy was found in one individual.

Systemic Features: 

This is a clinically heterogeneous disorder with extensive neurological deficits.  Patients have feeding and swallowing difficulties from the neonatal period.  There is intrauterine growth retardation and postnatally patients usually exhibit psychomotor delays and intellectual disabilities.  Some develop seizures and few achieve normal developmental milestones.  Axial hypotonia is present from early infancy and most patients have muscle weakness and atrophy.  However, there may be spastic quadriplegia which is often associated with dysmetria, tremor, and athetosis.  Ataxia eventually develops in most patients. 

Brain imaging shows cerebral and cerebellar atrophy, enlarged ventricles, white matter defects, and delayed myelination. 

Incomplete metabolic studies suggest there may be abnormalities in mitochondrial oxidative phosphorylation activity in at least some tissues.  Most patients have an elevated serum lactate.

Death in childhood is common.

Genetics

Homozygous and compound heterozygous mutations in the WARS2 gene have been found in several families with this condition.  The considerable variation in the phenotype may at least partially be explained by the fact that an additional variant in the W13G gene is sometimes present which impairs normal localization of the WARS2 gene product within mitochondria.

The transmission pattern in several families is consistent with autosomal recessive inheritance.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported for the general condition.

References
Article Title: 

Biallelic variants in WARS2 encoding mitochondrial tryptophanyl-tRNA synthase in six individuals with mitochondrial encephalopathy

Wortmann SB, Timal S, Venselaar H, Wintjes LT, Kopajtich R, Feichtinger RG, Onnekink C, Muhlmeister M, Brandt U, Smeitink JA, Veltman JA, Sperl W, Lefeber D, Pruijn G, Stojanovic V, Freisinger P, V Spronsen F, Derks TG, Veenstra-Knol HE, Mayr JA, Rotig A, Tarnopolsky M, Prokisch H, Rodenburg RJ. Biallelic variants in WARS2 encoding mitochondrial tryptophanyl-tRNA synthase in six individuals with mitochondrial encephalopathy. Hum Mutat. 2017 Dec;38(12):1786-1795.

PubMed ID: 
28905505

Pontocerebellar Hypoplasia 11

Clinical Characteristics
Ocular Features: 

Some patients are reported to have poor eye contact, hyperopia, and strabismus.  Three individuals had colobomas.  Strabismus, poor eye contact, and hyperopia have been noted in some individuals.   

Systemic Features: 

Microcephaly and large ears may be noted at birth.  Some patients have general hypotonia while others have spastic hypertonia.  Neurological features include markedly delayed psychomotor development, truncal and appendicular ataxia, and cognitive delays.  Developmental milestones such as walking, sitting, and speech are delayed.  Some patients have seizures.  A variety of behavior abnormalities have been reported including stereotypical movements, autistic behavior, repetitive motor movements, and poor communication.  Dysarthria and dysphagia are sometimes present.  There seems to be little progression of the neurological manifestations.

Brain MRIs reveal cerebellar hypoplasia and hypoplasia or agenesis of the corpus callosum in most patients.

Genetics

Homozygous mutations in the TBC1D23 gene (3q12.1q12.2) cause this disorder

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Homozygous Truncating Variants in TBC1D23 Cause Pontocerebellar Hypoplasia and Alter Cortical Development

Ivanova EL, Mau-Them FT, Riazuddin S, Kahrizi K, Laugel V, Schaefer E, de Saint Martin A, Runge K, Iqbal Z, Spitz MA, Laura M, Drouot N, Gerard B, Deleuze JF, de Brouwer APM, Razzaq A, Dollfus H, Assir MZ, Nitchke P, Hinckelmann MV, Ropers H, Riazuddin S, Najmabadi H, van Bokhoven H, Chelly J. Homozygous Truncating Variants in TBC1D23 Cause Pontocerebellar Hypoplasia and Alter Cortical Development. Am J Hum Genet. 2017 Sep 7;101(3):428-440.

PubMed ID: 
28823707

Al Kaissi Syndrome

Clinical Characteristics
Ocular Features: 

Reported facial dysmorphism features include periocular anomalies of ptosis, hypertelorism, down-slanting lid fissures, and epicanthal folds.  

Systemic Features: 

The phenotype is somewhat variable.  Intrauterine and postnatal growth retardation with hypotonia are common.   Moderate to severe intellectual disability is usually present and speech may be severely delayed.  The forehead is narrow, the nasal tip is broad, the nasal bridge is depressed, and the ears are low-set and posteriorly rotated.   Small hands and sometimes joint laxity are commonly present.  Cervical spine abnormalities including clefting, improper fusion, and segmentation anomalies are common.

Brain MRI may be normal but a small corpus callosum was present in some patients.

Genetics

Homozygous mutations in the CDK10 gene (16q24.3) are responsible for this disorder.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

CDK10 Mutations in Humans and Mice Cause Severe Growth Retardation, Spine Malformations, and Developmental Delays

Windpassinger C, Piard J, Bonnard C, Alfadhel M, Lim S, Bisteau X, Blouin S, Ali NB, Ng AYJ, Lu H, Tohari S, Talib SZA, van Hul N, Caldez MJ, Van Maldergem L, Yigit G, Kayserili H, Youssef SA, Coppola V, de Bruin A, Tessarollo L, Choi H, Rupp V, Roetzer K, Roschger P, Klaushofer K, Altmuller J, Roy S, Venkatesh B, Ganger R, Grill F, Ben Chehida F, Wollnik B, Altunoglu U, Al Kaissi A, Reversade B, Kaldis P. CDK10 Mutations in Humans and Mice Cause Severe Growth Retardation, Spine Malformations, and Developmental Delays. Am J Hum Genet. 2017 Sep 7;101(3):391-403.

PubMed ID: 
28886341

Carey-Fineman-Ziter Syndrome

Clinical Characteristics
Ocular Features: 

Abnormal eye movements with prominent external ophthalmoplegia are hallmarks of this disease.  An oculomotor nerve palsy with limited abduction and some degree of facial palsy are usually present.  The Moebius sequence is present in many patients.  Epicanthal folds, downslanting lid fissures, and ptosis are frequently seen.

Systemic Features: 

Clinical signs are highly variable.  Unusual facies with features of the Pierre Robin complex are characteristic.  Micrognathia and retrognathia are often present with glossoptosis.  Hypotonia and failure to thrive are commonly seen.  Dysphagia and even absent swallowing likely contribute to this.  Respiratory insufficiency can be present from birth, often with laryngostenosis, and some patients develop pulmonary hypertension and restrictive lung disease as adults.  Progressive scoliosis may contribute to this.  Many patients have club feet with joint contractures.  Skull formation consisting of microcephaly, or macrocephaly, or plagiocephaly is commonly seen.  Cardiac septal defects are common.

Intellectual disability is present in some but not all individuals.  Neuronal heterotopias, enlarged ventricles, reduced white matter, a small brainstem, microcalcifications, and enlarged ventricles have been observed.

Genetics

Homozygous or compound heterozygosity of the MYMK gene (9q34) is responsible for this condition.  

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment for the general disorder has been reported.

References
Article Title: 

A defect in myoblast fusion underlies Carey-Fineman-Ziter syndrome

Di Gioia SA, Connors S, Matsunami N, Cannavino J, Rose MF, Gilette NM, Artoni P, de Macena Sobreira NL, Chan WM, Webb BD, Robson CD, Cheng L, Van Ryzin C, Ramirez-Martinez A, Mohassel P, Leppert M, Scholand MB, Grunseich C, Ferreira CR, Hartman T, Hayes IM, Morgan T, Markie DM, Fagiolini M, Swift A, Chines PS, Speck-Martins CE, Collins FS, Jabs EW, Bonnemann CG, Olson EN; Moebius Syndrome Research Consortium, Carey JC, Robertson SP, Manoli I, Engle EC. A defect in myoblast fusion underlies Carey-Fineman-Ziter syndrome. Nat Commun. 2017 Jul 6;8:16077. doi: 10.1038/ncomms16077.

PubMed ID: 
28681861

Möbius sequence, Robin complex, and hypotonia: severe expression of brainstem disruption spectrum versus Carey-Fineman-Ziter syndrome

Verloes A, Bitoun P, Heuskin A, Amrom D, van de Broeck H, Nikkel SM, Chudley AE, Prasad AN, Rusu C, Covic M, Toutain A, Moraine C, Parisi MA, Patton M, Martin JJ, Van Thienen MN. Mobius sequence, Robin complex, and hypotonia: severe expression of brainstem disruption spectrum versus Carey-Fineman-Ziter syndrome. Am J Med Genet A. 2004 Jun 15;127A(3):277-87.

PubMed ID: 
15150779

Gaze Palsy, Familial Horizontal, with Progressive Scoliosis 2

Clinical Characteristics
Ocular Features: 

Strabismus is present at birth.  Horizontal eye movements are restricted but vertical gaze can be normal.  The optic nerves appear normal.

Systemic Features: 

Hypotonia may be noted at birth but ankle clonus and spasticity can develop later.  Progressive kyphoscoliosis has been diagnosed as early as the age of 4 years and may result in restrictive lung disease requiring spine surgery by the second decade of life.  Developmental milestones such as walking and talking are delayed and intellectual development is subnormal.  Mirror movements may be present.  Gait may be unsteady but can be normal.

Brain MRI reveals a variety of malformations.  Agenesis of the corpus callosum is present and the white matter tracts appear disorganized.  The superior cerebellar peduncles fail to decussate and transverse pontine fibers may be absent.  The pons and midbrain are hypoplastic while there is a midline cleft throughout the brainstem resulting in a butterfly-shaped medulla.

Genetics

Homozygous mutations in the DCC gene (18q21) are responsible for this condition.  Three patients in 2 unrelated consanguineous families have been reported.  Studies suggest that the DCC gene product is important for forebrain and brainstem midline crossing of neurons.

See Gaze Palsy, Familial Horizontal, with Progressive Scoliosis 1 (607313) for another disorder with somewhat similar features.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Biallelic mutations in human DCC cause developmental split-brain syndrome

Jamuar SS, Schmitz-Abe K, D'Gama AM, Drottar M, Chan WM, Peeva M, Servattalab S, Lam AN, Delgado MR, Clegg NJ, Zayed ZA, Dogar MA, Alorainy IA, Jamea AA, Abu-Amero K, Griebel M, Ward W, Lein ES, Markianos K, Barkovich AJ, Robson CD, Grant PE, Bosley TM, Engle EC, Walsh CA, Yu TW. Biallelic mutations in human DCC cause developmental split-brain syndrome. Nat Genet. 2017 Apr;49(4):606-612.

PubMed ID: 
28250456

Ayme-Gripp Syndrome

Clinical Characteristics
Ocular Features: 

Most patients have congenital cataracts which may be mild and "oil drop" in appearance.  The eyes appear far apart, the eyebrows are broad, and the palpebral fissures may slant upward or downward.  Ptosis has been reported.  Aphakic glaucoma has been reported in one juvenile who had unilateral cataract surgery at 5 months of age.

Systemic Features: 

The phenotype is heterogeneous and not all patients have all features.  The facial features are said to resemble those of the Down syndrome with brachycephaly, a high forehead, and a flat midface with shallow orbits and malar hypoplasia.  The ears are small, low-set, and posteriorly rotated.  The nose is short and the nasal bridge is broad and flat.  The mouth is small and the upper lip is thin.  The scalp hair may be sparse and the nails sometimes appear dystrophic.

The fingers are sometimes brachydactylous and tapered.  Short stature is common and the joints may have limited motion.  Dislocation of the radial heads is seen rarely while radioulnar synostosis has been seen in a few individuals.  Postnatal short stature is common.

Seizures often occur.  The ventricles appear large and cerebral atrophy has been reported.  Intellectual disability and mental retardation are common. However, at least one individual attended university although he had been diagnosed in childhood with Asberger disease.   Neurosensory hearing loss is common.

Genetics

This autosomal dominant condition results from heterozygous mutations in the MAF (16q32.2) gene.  At least one mother/son transmission event has been reported.

Many of the same features are seen in what has been called the Fine-Lubinsky syndrome (601353) but without mutations in the MAF gene.  It may not be a unique disorder.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No general treatment has been reported but specific anomalies such as cataracts should be addressed.

References
Article Title: 

Mutations Impairing GSK3-Mediated MAF Phosphorylation Cause Cataract, Deafness, Intellectual Disability, Seizures, and a Down Syndrome-like Facies

Niceta M, Stellacci E, Gripp KW, Zampino G, Kousi M, Anselmi M, Traversa A, Ciolfi A, Stabley D, Bruselles A, Caputo V, Cecchetti S, Prudente S, Fiorenza MT, Boitani C, Philip N, Niyazov D, Leoni C, Nakane T, Keppler-Noreuil K, Braddock SR, Gillessen-Kaesbach G, Palleschi A, Campeau PM, Lee BH, Pouponnot C, Stella L, Bocchinfuso G, Katsanis N, Sol-Church K, Tartaglia M. Mutations Impairing GSK3-Mediated MAF Phosphorylation Cause Cataract, Deafness, Intellectual Disability, Seizures, and a Down Syndrome-like Facies. Am J Hum Genet. 2015 May 7;96(5):816-25.

PubMed ID: 
25865493

Congenital Heart Defects, Dysmorphic Facies, and Intellectual Developmental Disorder

Clinical Characteristics
Ocular Features: 

The dysmorphic facial features primarily involve the periocular structures.  These include hypertelorism, ptosis, epicanthal folds, strabismus and upslanted palpebral fissures.

Systemic Features: 

Septal defects involving both the atrium and the ventricle are consistently present.  Pulmonary valve abnormalities are present in some patients.

Posteriorly rotated pinnae and a small mouth with a thin upper lip have been observed.  Camptodactyly and clinodactyly are common.  Some patients have mild microcephaly.

Global developmental delay is a consistent feature manifest as delays in walking and speech and eventual intellectual disability.  Feeding difficulties are common.  Hypotonia and hypermobile joints are often noted.  Imaging of the brain may reveal agenesis of the corpus callosum, incomplete formation of the inferior vermis, and leukomalacia of periventricular tissue.

Genetics

Heterozygous mutations have been identified in the CDK13 gene (7p14.1) in seven unrelated individuals.  Heterozygous parents may not have the full phenotype.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is available for the generalized condition.

References
Article Title: 

Distinct genetic architectures for syndromic and nonsyndromic congenital heart defects identified by exome sequencing

Sifrim A, Hitz MP, Wilsdon A, Breckpot J, Turki SH, Thienpont B, McRae J, Fitzgerald TW, Singh T, Swaminathan GJ, Prigmore E, Rajan D, Abdul-Khaliq H, Banka S, Bauer UM, Bentham J, Berger F, Bhattacharya S, Bu'Lock F, Canham N, Colgiu IG, Cosgrove C, Cox H, Daehnert I, Daly A, Danesh J, Fryer A, Gewillig M, Hobson E, Hoff K, Homfray T; INTERVAL Study., Kahlert AK, Ketley A, Kramer HH, Lachlan K, Lampe AK, Louw JJ, Manickara AK, Manase D, McCarthy KP, Metcalfe K, Moore C, Newbury-Ecob R, Omer SO, Ouwehand WH, Park SM, Parker MJ, Pickardt T, Pollard MO, Robert L, Roberts DJ, Sambrook J, Setchfield K, Stiller B, Thornborough C, Toka O, Watkins H, Williams D, Wright M, Mital S, Daubeney PE, Keavney B, Goodship J; UK10K Consortium., Abu-Sulaiman RM, Klaassen S, Wright CF, Firth HV, Barrett JC, Devriendt K, FitzPatrick DR, Brook JD; Deciphering Developmental Disorders Study., Hurles ME. Distinct genetic architectures for syndromic and nonsyndromic congenital heart defects identified by exome sequencing. Nat Genet. 2016 Sep;48(9):1060-5.

PubMed ID: 
27479907

Epileptic Encephalopathy, Early Infantile 48

Clinical Characteristics
Ocular Features: 

Poor eye contact is present from infancy.  Optic atrophy has been reported in several patients and features of retinitis pigmentosa were present in sibs of one family.

Systemic Features: 

Infants usually present with hypotonia and feeding difficulties.  Global developmental delay is also noted early and becomes more obvious with time.  Seizures are often seen early and become intractable.  Many individuals have microcephaly.  Hypermobility with dyskinesias and hyporeflexia are often present.  Speech is generally absent and many individuals are unable to sit or walk.

Brain imaging often shows atrophy of the cerebrum and cerebellum accompanied by enlarged ventricles and a thin corpus callosum.

Genetics

Homozygous or compound heterozygous mutations in the AP3B2 gene (15q25.2) can be responsible for this condition.

For another somewhat similar condition see early onset epileptic encephalopathy 28 (616211) with autosomal recessive inheritance.  For an autosomal dominant condition with a similar clinical picture, see early onset epileptic encephalopathy 47 (617166).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Autosomal-Recessive Mutations in AP3B2, Adaptor-Related Protein Complex 3 Beta 2 Subunit, Cause an Early-Onset Epileptic Encephalopathy with Optic Atrophy

Assoum M, Philippe C, Isidor B, Perrin L, Makrythanasis P, Sondheimer N, Paris C, Douglas J, Lesca G, Antonarakis S, Hamamy H, Jouan T, Duffourd Y, Auvin S, Saunier A, Begtrup A, Nowak C, Chatron N, Ville D, Mireskandari K, Milani P, Jonveaux P, Lemeur G, Milh M, Amamoto M, Kato M, Nakashima M, Miyake N, Matsumoto N, Masri A, Thauvin-Robinet C, Riviere JB, Faivre L, Thevenon J. Autosomal-Recessive Mutations in AP3B2, Adaptor-Related Protein Complex 3 Beta 2 Subunit, Cause an Early-Onset Epileptic Encephalopathy with Optic Atrophy. Am J Hum Genet. 2016 Dec 1;99(6):1368-1376.

PubMed ID: 
27889060

Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield

Anazi S, Maddirevula S, Faqeih E, Alsedairy H, Alzahrani F, Shamseldin HE, Patel N, Hashem M, Ibrahim N, Abdulwahab F, Ewida N, Alsaif HS, Al Sharif H, Alamoudi W, Kentab A, Bashiri FA, Alnaser M, AlWadei AH, Alfadhel M, Eyaid W, Hashem A, Al Asmari A, Saleh MM, AlSaman A, Alhasan KA, Alsughayir M, Al Shammari M, Mahmoud A, Al-Hassnan ZN, Al-Husain M, Osama Khalil R, Abd El Meguid N, Masri A, Ali R, Ben-Omran T, El Fishway P, Hashish A, Ercan Sencicek A, State M, Alazami AM, Salih MA, Altassan N, Arold ST, Abouelhoda M, Wakil SM, Monies D, Shaheen R, Alkuraya FS. Clinical genomics expands the morbid genome of intellectual disability and offers a high diagnostic yield. Mol Psychiatry. 2016 Jul 19. doi: 10.1038/mp.2016.113. [Epub ahead of print].

PubMed ID: 
27431290

Encephalopathy, Early-Onset, With Brain Atrophy and Thin Corpus Callosum

Clinical Characteristics
Ocular Features: 

Optic atrophy is present in many patients and may be present early since lack of visual tracking or eye contact may be noted at birth.  Sparse eyebrows, upslanting palpebral fissures, and hypertelorism have also been reported.

Systemic Features: 

Severe hypotonia is present at birth often causing respiratory distress in the neonate.  Spasticity can develop later.  Growth failure with progressive microcephaly is present in infants.  Brain imaging often reveals diffuse atrophy of structures including the cerebellum, brainstem, spinal cord, and cerebrum.  Tongue fasciculations have been observed.   Micrognathia and widely spaced teeth are sometimes present.  Several patients have died during infancy.

Genetics

Homozygous mutations in the TBCD (17q25.3) are responsible for this disorder.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Biallelic Mutations in TBCD, Encoding the Tubulin Folding Cofactor D, Perturb Microtubule Dynamics and Cause Early-Onset Encephalopathy

Flex E, Niceta M, Cecchetti S, Thiffault I, Au MG, Capuano A, Piermarini E, Ivanova AA, Francis JW, Chillemi G, Chandramouli B, Carpentieri G, Haaxma CA, Ciolfi A, Pizzi S, Douglas GV, Levine K, Sferra A, Dentici ML, Pfundt RR, Le Pichon JB, Farrow E, Baas F, Piemonte F, Dallapiccola B, Graham JM Jr, Saunders CJ, Bertini E, Kahn RA, Koolen DA, Tartaglia M. Biallelic Mutations in TBCD, Encoding the Tubulin Folding Cofactor D, Perturb Microtubule Dynamics and Cause Early-Onset Encephalopathy. Am J Hum Genet. 2016 Oct 6;99(4):962-973.

PubMed ID: 
27666370

Biallelic TBCD Mutations Cause Early-Onset Neurodegenerative Encephalopathy

Miyake N, Fukai R, Ohba C, Chihara T, Miura M, Shimizu H, Kakita A, Imagawa E, Shiina M, Ogata K, Okuno-Yuguchi J, Fueki N, Ogiso Y, Suzumura H, Watabe Y, Imataka G, Leong HY, Fattal-Valevski A, Kramer U, Miyatake S, Kato M, Okamoto N, Sato Y, Mitsuhashi S, Nishino I, Kaneko N, Nishiyama A, Tamura T, Mizuguchi T, Nakashima M, Tanaka F, Saitsu H, Matsumoto N. Biallelic TBCD Mutations Cause Early-Onset Neurodegenerative Encephalopathy. Am J Hum Genet. 2016 Oct 6;99(4):950-961.

PubMed ID: 
27666374

Optic Atrophy 11

Clinical Characteristics
Ocular Features: 

Optic atrophy is seen as early as 5 years of age but may be congenital in origin as hypoplasia of the optic nerve was present in all patients.  Three of 4 affected children also were myopic.

Systemic Features: 

This is a form of mitochondriopathy with considerable clinical heterogeneity.  A single consanguineous family with 4 affected children of ages 5-16 years of age has been reported.

Common features include short stature, microcephaly (1 had macrocephaly), hearing impairment. Ataxia, dysmetria, and athetotic movements may be present.  Motor and mental development are delayed as is expressive speech.  Intellectual disability is present in all 4 patients.  Leukoencephalopathy was seen in all patients and one had brain atrophy.  Cerebellar hypoplasia was present in 2 of four patients.

Muscle mitochondria in one patient had morphologic changes.  Lactate levels and lactate/pyruvate ratios were elevated in the blood and CSF fluid of three patients.

Genetics

Homozygous mutations in the YME1L1 gene (10p12.1) were responsible for this condition in 4 offspring of a consanguineous Saudi Arabian family.   This is a nuclear encoded mitochondrial gene.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.Hom

References
Article Title: 

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