intellectual disability

Beare-Stevenson Syndrome

Clinical Characteristics
Ocular Features: 

The midface hypoplasia and shallow orbits result in the appearance of prominent eyes.  Ptosis and hypertelorism have been reported while the palpebral fissures are downslanting. One patient has been reported to have optic atrophy.  Another patient was described with cloudy corneas, irregular irides and nonreactive pupils.

Systemic Features: 

Pregnancies may be complicated by polyhydramnios.  Infants are born with craniosynostosis with a cloverleaf pattern usually.  The skull is often shortened in the anteroposterior axis with flattening of the occipital region.  The skin is deeply furrowed with the cutis gyrata patterns most prominent in the posterior scalp but also present on the palms, soles, pinnae, and elsewhere.  Acanthosis nigricans is often present.

There is midface hypoplasia and nearly all individuals have intellectual disability.

The external ear canals can be atretic, the nares are often anteverted, and the mouth may be small.  An excess number of neonatal teeth and hypoplastic nails have been noted.  Hydrocephalus is common.  The umbilical stump is often unusually prominent.  Anogenital anomalies such as an anteriorly placed anus, cryptorchidism, and bifid scrotum may be present.  Pyloric stenosis is sometimes present.

Upper airway obstruction with respiratory distress may necessitate a tracheotomy. A cartilaginous tracheal sleeve replacing the normal C rings of cartilage has been found in several infants. These can be difficult to detect and their presence may have been responsible for breathing restrictions that has led to the demise of some children before two years of age.

Genetics

Reported cases have occurred sporadically.  Increased paternal age has been suggested as a factor in the occurrence of heterozygous mutations in the FGFR2 gene (10q26.13) which have been identified in some individuals.

Other forms of craniosynostosis in which mutations in FGFR2 have been found are: Crouzon Syndrome (123500), Pfeiffer Syndrome (101600), Apert Syndrome (101200), Jackson-Weiss Syndrome (123150), and Saethre-Chotzen Syndrome (101400).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

There is no general treatment for this syndrome.  Several infants have had tracheotomies and CNS shunts.

References
Article Title: 

Beare-Stevenson cutis gyrata syndrome

Hall BD, Cadle RG, Golabi M, Morris CA, Cohen MM Jr. Beare-Stevenson cutis gyrata syndrome. Am J Med Genet. 1992 Sep 1;44(1):82-9. PubMed PMID: 1519658.

PubMed ID: 
1519658

Filippi Syndrome

Clinical Characteristics
Ocular Features: 

The ocular features have not been fully described.  The most consistent features are long eyelashes, thick (bushy) eyebrows, and 'visual disturbance'.  Most individuals have a facial dysmorphism which includes a broad nasal base suggestive of hypertelorism.  Optic atrophy and proptosis have been noted. 

Systemic Features: 

Intrauterine growth retardation is sometimes seen.  Microcephaly, short stature, syndactyly, intellectual disability (often labeled mental retardation), and a dysmorphic face are characteristic.  Some individuals have cryptorchidism, seizures, and ectodermal abnormalities including nail hypoplasia, hirsutism, and microdontia.  Mental and physical delays are common.  The syndactyly usually involves only soft tissue between toes 2, 3, and 4 and fingers 3 and 4 accompanied by clinodactyly of the 5th finger.  Polydactyly is sometimes present while radiologically the radial head may show evidence of hypoplasia. 

Genetics

Homozygosity or compound heterozygosity in the CKAP2L gene (2q13) segregates with this phenotype. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is known.

References
Article Title: 

Mutations in CKAP2L, the human homolog of the mouse Radmis gene, cause Filippi syndrome

Hussain MS, Battaglia A, Szczepanski S, Kaygusuz E, Toliat MR, Sakakibara S, Altmuller J, Thiele H, Nurnberg G, Moosa S, Yigit G, Beleggia F, Tinschert S, Clayton-Smith J, Vasudevan P, Urquhart JE, Donnai D, Fryer A, Percin F, Brancati F, Dobbie A, Smigiel R, Gillessen-Kaesbach G, Wollnik B, Noegel AA, Newman WG, Nurnberg P. Mutations in CKAP2L, the human homolog of the mouse Radmis gene, cause Filippi syndrome. Am J Hum Genet. 2014 Nov 6;95(5):622-32.

PubMed ID: 
25439729

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

Cataracts, Congenital, with Intellectual Disability

Clinical Characteristics
Ocular Features: 

Reported patients have bilateral posterior polar lens opacification, presumably present since birth.  No other ocular abnormalities are present.  Vision is stated to be normal following early cataract extractions.  No glaucoma has been detected while spectral OCT and electrophysiological studies had normal results.

Systemic Features: 

Psychomotor disabilities and developmental delays are present.  Walking does not occur until the age of about 2 years and speech is present by 5 years.  No dysmorphic features or other organ disease are present.  MRI studies of the brain are normal.

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the STX3 gene (11q12.1).  It has been reported in three children in a consanguineous Tunisian family.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Surgical removal of the cataracts should be considered when visually significant.  Special education might be helpful as learning difficulties have been noted.

References
Article Title: 

Optic Atrophy with Intellectual Disability

Clinical Characteristics
Ocular Features: 

Optic atrophy is the primary ocular abnormality but visual deficits are said to originate from cortical impairment.  The optic discs are pale and may be small with excavation.  Strabismus and latent nystagmus are often present. Up slanting palpebral fissures and epicanthal folds have been noted. Visual acuity levels have not been reported.

Systemic Features: 

Facial dysmorphism of a non-specific pattern can be present as evidenced by protruding ears with helical anomalies, and a small, sometimes elevated nasal bridge. The fingers are small and tapered.  Developmental delay is common.  Obsessive-compulsive behavior and autistic features have been reported in a single individual.  Hypotonia may be present.

Genetics

This is an autosomal dominant disorder resulting from heterozygous mutations in the NR2F1 gene (5q15), a transcription regulator.   Six persons with this condition have so far been reported.  The gene product is a nuclear protein active in transcription regulation during neurodevelopment.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Only symptomatic treatment is available.  Low vision aids and special education may be of benefit.

References
Article Title: 

NR2F1 mutations cause optic atrophy with intellectual disability

Bosch DG, Boonstra FN, Gonzaga-Jauregui C, Xu M, de Ligt J, Jhangiani S, Wiszniewski W, Muzny DM, Yntema HG, Pfundt R, Vissers LE, Spruijt L, Blokland EA, Chen CA; Baylor-Hopkins Center for Mendelian Genomics, Lewis RA, Tsai SY, Gibbs RA, Tsai MJ, Lupski JR, Zoghbi HY, Cremers FP, de Vries BB, Schaaf CP. NR2F1 mutations cause optic atrophy with intellectual disability. Am J Hum Genet. 2014 Feb 6;94(2):303-9.

PubMed ID: 
24462372

Microphthalmia and Anophthalmia, ALDH1A3 Associated

Clinical Characteristics
Ocular Features: 

Patients have a variety of ocular malformations including microphthalmia and clinical anophthalmia.  Some have orbital cysts. Imaging may reveal hypoplastic optic nerves and chiasms.

Systemic Features: 

Both cardiac (pulmonary stenosis and septal defects) and neurological deficits (autism spectrum disorders and 'intellectual disability') have been reported.  Birth weight and head circumference are often low.  However, brain imaging has revealed no consistent malformations.

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the gene ALDH1A3 (15q26.3) which encodes the enzyme retinaldehyde dehydrogenase.  Mutations in ALDH1A3 impair the enzymatic oxidation of retinaldehyde important to the synthesis of retinoic acid, a key signaling molecule in eye development. 

However, mutations in other genes important to ocular development such as GJA3 and SOX2 (a transcription factor) may result in a similar phenotype.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment for the ocular problems is available.

References
Article Title: 

ALDH1A3 Mutations Cause Recessive Anophthalmia and Microphthalmia

Fares-Taie L, Gerber S, Chassaing N, Clayton-Smith J, Hanein S, Silva E, Serey M, Serre V, G?(c)rard X, Baumann C, Plessis G, Demeer B, Br?(c)tillon L, Bole C, Nitschke P, Munnich A, Lyonnet S, Calvas P, Kaplan J, Ragge N, Rozet JM. ALDH1A3 Mutations Cause Recessive Anophthalmia and Microphthalmia. Am J Hum Genet. 2013 Feb 7;92(2):265-70.

PubMed ID: 
23312594

Danon Disease

Clinical Characteristics
Ocular Features: 

The ocular features of Danon disease are less well known than the systemic manifestations and are as yet not fully delineated likely because not all patients have visual symptoms or fundus changes.  The most commonly described fundus abnormalities are pigmentary changes variously called a peripheral pigmentary retinopathy or a pigmentary atrophy in some cases.   Changes in pigmentation may be mild in both affected males and carrier females, but are generally more severe in males.  A bulls-eye maculopathy and color vision deficiencies have been described.  Loss of visual acuity is variable and may lead to symptoms before myopathy is evident.  Vision loss is usually progressive and may be reduced to hand motions.  OCT shows thinning of the photoreceptor and RPE layers.  The full field ERG is reduced in amplitude consistent with a generalized cone-rod dystrophy.

Systemic Features: 

This disorder, originally believed to be a type of glycogen storage disease, is actually a form of autophagic vacuolar myopathy.    The characteristic vacuoles are found in muscle cytoplasm surrounded by sarcolemmal proteins and basal lamina.  The primary extraocular disease occurs in the myocardium although skeletal muscle may also be involved.  Intellectual disability is a variable and inconsistent feature.  

Cardiac rhythm abnormalities are common and include AV nodal block, atrial fibrillation, and Wolff-Parkinson-White EKG findings.  Hypertrophic cardiomyopathy (and sometimes dilated cardiomyopathy) with primary involvement of the left ventricle is common.  Symptoms typically occur in males before the age of 20 years and somewhat later in females.

Some patients have muscular weakness and exercise intolerance.  Diagnosis can be made when the characteristic vacuoles are present in a muscle biopsy but their absence does not rule out the diagnosis.

Genetics

This is an X-linked dominant disorder caused by mutations in LAMP2 (Xp24).  Females are generally less severely affected than males. Most men with Danon disease have some intellectual disability as well as skeletal myopathy but these features are found in less than half of affected women.  

Pedigree: 
X-linked dominant, father affected
X-linked dominant, mother affected
Treatment
Treatment Options: 

No known treatment is available for the ocular disease.  Transplantation can be an effective treatment for the cardiomyopathy which can be lethal even in adolescents.

References
Article Title: 

Cardiac arrhythmias in patients with Danon disease

Konrad T, Sonnenschein S, Schmidt FP, Mollnau H, Bock K, Ocete BQ, Munzel T, Theis C, Rostock T. Cardiac arrhythmias in patients with Danon disease. Europace. 2016 Oct 14. pii: euw215.

PubMed ID: 
27742774

Cone-rod dystrophy in Danon disease

Brodie S. Cone-rod dystrophy in Danon disease. Graefes Arch Clin Exp Ophthalmol. 2012 Mar 10. [Epub ahead of print].

PubMed ID: 
22407291

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