hearing impairment

Pontocerebellar Hypoplasia 3

Clinical Characteristics
Ocular Features: 

Optic atrophy is an inconsistent feature (sometimes even unilateral) of patients with PCH.  Cortical blindness has also been described.  There may be dysmorphic facial features such as wide palpebral fissures, epicanthal folds, and prominent eyes. 

Systemic Features: 

Infants are generally small and hypotonic at birth.  The skull is small and often brachycephalic.  The ears are large and low-set and  facial dysmorphism (full cheeks, long philtrum) is present.  Infants have poor head control and truncal ataxia.  Later, hyperreflexia and spasticity become evident.  Seizures are common.  Developmental delays, both somatic and mental, are nearly universal and large joint contractures are often seen. Many of these signs are progressive.  

Brain imaging generally reveals cerebral and cerebellar atrophy, a hypoplastic corpus callosum, a small cerebellar vermis, and a hypoplastic brainstem.  Short stature is a feature and early death often occurs.

Genetics

PCH3 is one of at least 10 syndromes belonging to a clinically and genetically heterogeneous group of conditions known as pontocerebellar hypoplasias.  Members of this group, while individually rare, nevertheless collectively account for a significant proportion of what was once labeled cerebral palsy.

PCH3 results from homozygous mutations in the PCLO gene (7q21). 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for the general disorder.

References
Article Title: 

Loss of PCLO function underlies pontocerebellar hypoplasia type III.

Ahmed MY, Chioza BA, Rajab A, Schmitz-Abe K, Al-Khayat A, Al-Turki S, Baple EL, Patton MA, Al-Memar AY, Hurles ME, Partlow JN, Hill RS, Evrony GD, Servattalab S, Markianos K, Walsh CA, Crosby AH, Mochida GH. Loss of PCLO function underlies pontocerebellar hypoplasia type III. Neurology. 2015 Apr 28;84(17):1745-50.

PubMed ID: 
25832664

Mental Retardation, AD 34

Clinical Characteristics
Ocular Features: 

Patients may have upslanting lid fissures, epicanthus, ptosis, synophrys, and cortical visual impairment.

Systemic Features: 

Among the three reported individuals with the COL4A3BP mutation, one had postnatal microcephaly, widely spaced teeth, synophrys, and intellectual disability. Another had trunk hypotonia, global developmental delay, wide intermamillary distance, 2-3 toe syndactyly, tonic-clonic seizures, and myopathic facies. The third had a broad-based gait, coarse and curly hair, tonic-clonic seizures, and global developmental delay. 

Genetics

In a screening study of 1133 children with severe undiagnosed developmental conditions, three males were found with heterozygous mutations in the COL4A3BP gene (5q13).  Family history data are not given for these three individuals but autosomal dominant transmission seems to be a reasonable assumption.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

Supportive care is required but no other treatment has been reported.

References
Article Title: 

Axenfeld-Rieger Anomaly, Plus

Clinical Characteristics
Ocular Features: 

This rare disorder has ocular features of Rieger anomaly with significant systemic features but different than those found in the Axenfeld-Rieger syndrome.  The iris is hypoplastic and the pupil may be distorted secondary to anterior synechiae.  Schwalbe line is prominent.  There are no reports of glaucoma but this may be biased by the small number of patients reported.  Hypertelorism, prominent eyes and strabismus have been described.  Several patients have had absence of the extraocular muscles.

Systemic Features: 

Hypotonia, lax joints, midface hypoplasia, prominent forehead, and short stature have been described.  Some, but not all patients have a degree of psychomotor retardation.  Mild hearing impairment has been reported.

Genetics

This is likely an autosomal dominant disorder in which mutations of the PITX2 and FOXC1 genes common in Axenfeld-Rieger syndrome have been ruled out.  No locus has been identified.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No treatment is available.

References
Article Title: 

Baller-Gerold Syndrome

Clinical Characteristics
Ocular Features: 

The ocular features are a rather minor part of this syndrome and are found in less than a third of patients.  These primarily involve lids and adnexae with telecanthus, downslanting lid fissures, and epicanthal folds.  Some individuals have nystagmus while strabismus, blue sclerae, and ectropion have also been reported.

Systemic Features: 

The cardinal features of this syndrome are craniosynostosis and radial defects.  However, a large number of variable defects such as imperforate or anteriorly placed anus, rectovaginal fistula, absent thumbs, polydactyly, and mental retardation may also be present.  The radius may be completely absent or abnormally formed and occasionally the ulnar bone is involved as well.  Some patients have a conductive hearing loss.

Genetics

This syndrome is caused by a mutation in the RECQL4 gene at 8q24.3 and seems to be an autosomal recessive disorder.  Its syndromal status as a unique syndrome is in some doubt because of considerable phenotypic overlap with other entities such as Roberts (268300) and Saethre-Chotzen (101400) syndromes.  The latter however is caused by a mutation in the TWIST1 gene and the former by mutations in the ESCO2 gene.

The same gene is mutated in Rothmund-Thomson syndrome (268400) suggesting allelism of the two disorders.  The phenotype is vastly different in the two disorders however.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available.

References
Article Title: 

Apert Syndrome

Clinical Characteristics
Ocular Features: 

In 10% of patients, keratitis and corneal scarring occur from the sometimes marked proptosis and corneal exposure.  Optic atrophy is present in over 20% of patients.  Strabismus, primarily exotropia, is found in more than 70% and various extraocular muscle anomalies may be detectable.  Usually the exotropia has a V-pattern with overaction of the inferior oblique muscles while the superior oblique is weak.  Amblyopia occurs in nearly 20%.  The lid fissures often slant downward and the eyebrows may be interrupted.

Systemic Features: 

This brachysphenocephalic type of acrocephaly is associated with syndactyly in the hands and feet.  Pre- and postaxial polydactyly may be present.  There is considerable variation in expression with some patients so mildly affected that they appear virtually normal, whereas others have extreme degrees of brachycephaly with high foreheads, midface hypoplasia, and proptosis secondary to shallow orbits.  Imaging often reveals one or more CNS anomalies such as defects of the corpus callosum, partial absence of the septum pellucidum, ventriculomegaly, and sometimes hydrocephalus.  A small but significant proportion of patients have some developmental delay and cognitive impairment.  Over 39% of patients have a normal IQ.

Genetics

This type of craniosynostosis is caused by mutations in the fibroblast growth factor receptor-2 gene, FGFR2, located at 10q26.13.  It is generally considered an autosomal dominant disorder based on familial cases but most occur sporadically.  A paternal age effect on mutations has been found.  The same gene is mutant in allelic disorders sometimes clinically separated and labeled Crouzon (123500) and Pfeiffer (some cases) (101600) syndromes.  Jackson-Weiss syndrome (123150) maps to the same locus.  However, this entire group has many overlapping features making classification on clinical grounds alone difficult.  Only Apert syndrome is caused by mutations in a single gene whereas other syndromes seem to result from mutations in multiple genes.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No specific treatment is available for this disorder but exposure keratitis may require surveillance and therapy.

References
Article Title: 

Axenfeld-Rieger Syndrome, Type 2

Clinical Characteristics
Ocular Features: 

As in RIEG1 and RIEG3, glaucoma is the most serious ocular problem.  In a large family with 11 affected members, 9 had glaucoma.  All had the classic ocular signs of anterior segment dysgenesis, primarily posterior embryotoxon and iris adhesions (for a full description of the ocular features see Axenfeld-Rieger syndrome, RIEG1 [180500]).

Systemic Features: 

Oligodontia, microdontia, and premature loss of teeth are common in type 2.  Maxillary hypoplasia is less common as is hearing loss.  Umbilical anomalies were not present in any affected individuals.  Cardiac defects are rare.

Genetics

This is an autosomal dominant disorder as in the other types.  The locus is at 13q14 but no molecular defect has been defined.  At least two individuals purported to have type 2 were found to have deletions of this segment of chromosome 13.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The high risk of glaucoma demands lifelong monitoring of intraocular pressure.

References
Article Title: 

Stickler Syndrome, Type I

Clinical Characteristics
Ocular Features: 

High myopia and vitreous degeneration dominate the ocular manifestations of Stickler syndrome, type I.  The vitreous often appears optically empty as it liquefies and the fibrils degenerate.  The vitreous is sometimes seen to form ‘veils’, especially in the retrolenticular region but they may also float throughout the posterior chamber.  They are often attached to areas of lattice degeneration in the retina as well as other areas.  Posterior vitreous detachments are common.  Vitreoretinal degeneration is progressive and by the second decade rhegmatogenous detachments occur in half of affected patients.  As many as three quarters of adult patients have retinal breaks.  The retina has pigmentary changes with deposition circumferentially near the equator and more peripherally.  Hypopigmentation is more common early creating a tessellated appearance.  Lenticular opacities occur also early with cortical flecks and wedge-shaped changes.

The ERG may be normal early but evidence of rod and cone dysfunction soon appears and is progressive.  Dark adaptation is defective later in the course of the disease.  The EOG is virtually always depressed.  The visual field is constricted and may show a ring scotoma coincident with the equatorial chorioretinal atrophy.

Systemic Features: 

It has been suggested that there is a nonsyndromic or ocular type of Stickler syndrome lacking many of the extraocular features characteristic of the complete syndrome.  However, the evidence for the ocular type described here as a distinct entity remains slim and the clinical picture may simply reflect variable expressivity of mutations in the same gene.  Type I Stickler syndrome has multiple systemic features such as cleft palate, hearing impairment, premature arthritis, micrognathia, kyphoscoliosis, and some signs such as arachnodactyly that are found in the Marfan syndrome.

Genetics

This is an autosomal dominant disease of collagen formation as a result of mutations in the COL2A1 gene (12q13.11-q13.2). The mutations causing both syndromal and the suggested nonsyndromal ocular type of Stickler disease are in the same gene.  Mutations in the same gene are known to cause autosomal dominant rhegmatogenous retinal detachments in patients who have none of the systemic clinical signs (609508).  These patients may lack the signs of vitreous degeneration seen in Kniest dysplasia (156550)  and in the disorder described here.

There is better evidence for a second type of Stickler syndrome, STL2 or type II (604841) based on phenotypic differences and the fact that a second locus (1p21) containing mutations in COL11A1 has been linked to it. 

Type III is caused by mutations in COL11A2 and has systemic features similar to types I and II but lacks the eye findings since this gene is not expressed in the eye.

Type IV also has important ocular features but is an autosomal recessive disorder caused by mutations in COL9A2.

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The combination of progressive vitreoretinal degeneration, frequency of posterior vitreous detachments, and axial myopia creates a lifelong threat of retinal tears and detachments.   Half to three quarters of all patients develop retinal tears and detachments.  Certainly all patients with Stickler syndrome deserve repeated and thorough retinal exams throughout their lives.  In addition to prompt treatment of tears and detachments, some have advocated prophylactic scleral banding to reduce vitreous traction, or applying 360 degree cryotherapy.

References
Article Title: 

High efficiency of mutation detection in type 1 stickler syndrome using a two-stage approach: vitreoretinal assessment coupled with exon sequencing for screening COL2A1

Richards AJ, Laidlaw M, Whittaker J, Treacy B, Rai H, Bearcroft P, Baguley DM, Poulson A, Ang A, Scott JD, Snead MP. High efficiency of mutation detection in type 1 stickler syndrome using a two-stage approach: vitreoretinal assessment coupled with exon sequencing for screening COL2A1. Hum Mutat. 2006 Jul;27(7):696-704. Erratum in: Hum Mutat. 2006 Nov;27(11):1156.

PubMed ID: 
16752401
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