diastema

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: 

Kaufman Oculocerebrofacial Syndrome

Clinical Characteristics
Ocular Features: 

Alterations in the morphology of periocular structures is the most consistent ocular feature.  These include epicanthal folds, upward-slanting lid fissures, ptosis, blepharophimosis, sparse eyebrows, and telecanthus.  However, pale optic discs, iris colobomas, microcornea, strabismus, nystagmus, and hypertelorism are variably present. 

Systemic Features: 

There is both intrauterine and postnatal growth retardation.  Hypotonia is often noted along with general psychomotor delays.  Neonatal respiratory distress and laryngeal stridor may be present.  The intellectual disability can be severe.  Corpus callosum aplasia and hypoplasia have been reported.  Microcephaly and brachycephaly with delayed suture closure are features.  The face is long and narrow and the mouth is disproportionally large.  A high arched palate can be present and the pinnae are often deformed, posteriorly rotated and may be accompanied by preauricular skin tags. The teeth appear widely spaced (diastema) and the lower jaw is underdeveloped.

Genetics

Kaufman BPIDS syndrome results from homozygous or compound heterozygous mutations in the UBE3B gene (12q23).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

No general treatment is available although repair of some specific malformations is possible.

References
Article Title: 

Deficiency for the ubiquitin ligase UBE3B in a blepharophimosis-ptosis-intellectual-disability syndrome

Basel-Vanagaite L, Dallapiccola B, Ramirez-Solis R, Segref A, Thiele H, Edwards A, Arends MJ, Miro X, White JK, Desir J, Abramowicz M, Dentici ML, Lepri F, Hofmann K, Har-Zahav A, Ryder E, Karp NA, Estabel J, Gerdin AK, Podrini C, Ingham NJ, Altmuller J, Nurnberg G, Frommolt P, Abdelhak S, Pasmanik-Chor M, Konen O, Kelley RI, Shohat M, Nurnberg P, Flint J, Steel KP, Hoppe T, Kubisch C, Adams DJ, Borck G. Deficiency for the ubiquitin ligase UBE3B in a blepharophimosis-ptosis-intellectual-disability syndrome. Am J Hum Genet. 2012 Dec 7;91(6):998-1010.

PubMed ID: 
23200864

An oculocerebrofacial syndrome

Kaufman RL, Rimoin DL, Prensky AL, Sly WS. An oculocerebrofacial syndrome. Birth Defects Orig Artic Ser. 1971 Feb;7(1):135-8.

PubMed ID: 
5006210

Mannosidosis, Alpha B

Clinical Characteristics
Ocular Features: 

Many (probably most) patients have lens opacities and some have corneal opacities as well.  Nystagmus and strabismus have been described.  Pigmentary changes of a mottled nature can be present in the posterior pole and may be associated with retinal vessel attenuation and diminished ERG responses.  Retinal thinning can be demonstrated.  A mixture of hypo- and hyperautofluorescence is often visible.  Mild optic atrophy has been seen.  There is evidence for progressive visual loss, even late in life.  Eyebrows appear thick.    

Systemic Features: 

Mannosidosis is a highly variable multisystem disorder.  Onset may be in infancy but in other patients symptoms appear later in the first decade.  Progression of disease is more rapid in individuals with early onset (type 3) with rapid mental, motor deterioration and early death.  The characteristic coarse facial features usually are evident later in milder cases (types 1 and 2) that have mild or moderate intellectual disabilities.  Regardless, mannosidosis is relentlessly progressive with mental deterioration and motor disabilities.  Ataxia is a common feature.  Dental anomalies (diastema), large ears, macroglossia, joint stiffness,, hepatosplenomegaly, enlarged head circumference, hearing loss (sensorineural), increased susceptibility to infections, dysarthria, and spondylolysis may be present.

Genetics

Alpha-mannosidoosis is an autosomal recessive lysosomal storage disorder resulting from mutations in the MAN2B1 gene (19p13.2).  There is another form of mannosidosis known as beta A  (248510) caused by mutations in MANBA but ocular features have not been reported.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Prompt treatment for infections is required and prophylactic vaccinations are indicated.  All individuals should be seen annually and assistive devices such as wheel chairs and hearing aids prescribed when needed.

Nance-Horan Syndrome

Clinical Characteristics
Ocular Features: 

Congenital cataracts are a feature of this X-linked disorder.  These consist of bilateral, dense nuclear opacification (in most males) but sutural opacities are also seen, especially in carrier females.  If the nuclear cataracts are not treated promptly, severe amblyopia, nystagmus, and strabismus may result.  Microcornea, congenital glaucoma, scleral staphylomas, and retinal cystoid degeneration may also be present.  Microphthalmia has been described. These ocular signs are present in 90% of heterozygous females but they may be subtle and careful examination is required to identify them.  Cataract surgery is usually not required in females. 

Systemic Features: 

This is a developmental disorder in which facial dysmorphism and dental anomalies are consistent systemic features in affected males.  Some patients (30%) also have some intellectual impairment while others have developmental delays and behavior problems.  The pinnae may be anteverted and often appear large while the nose and nasal bridge are prominent.  The teeth in males are small and pointed or 'screwdriver shaped' and are widely separated (sometimes called Hutchinson teeth).  The enamel may be hypoplastic and dental agenesis can be present.  Supernumerary incisors have been described.  The facial and dental features may be present in female carriers but are less pronounced.  Females do not have intellectual impairment. 

Genetics

This is an X-linked recessive (dominant?) disorder resulting from mutations in the NHS gene located at Xp22.13.  However, heterozygous females may have clinical manifestations, including dense cataracts, and all offspring of such females need ophthalmological evaluations at birth.

It is likely that at least some cases of X-linked congenital cataract (CXN; 302200) represent this disorder because the facial dysmorphism may be subtle and easily missed in Nance-Horan.  Of course, the two disorders may also be allelic.  A variety of alterations in the NHS gene, including copy number variations, intragenic deletions, and duplication/triplication arrangements, have been found.  The occasionally subtle facial dysmorphology and the dental abnormalities are easily missed in patients in whom congenital cataracts are the primary clinical concern.  

Pedigree: 
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

Visually significant cataracts should be removed early to allow for normal visual maturation.  Glaucoma must be treated appropriately.  At risk males and females should have dental X-rays and dental surgery may be required.  Special education may be beneficial in males. 

References
Article Title: 

X-linked cataract and Nance-Horan syndrome are allelic disorders

Coccia M, Brooks SP, Webb TR, Christodoulou K, Wozniak IO, Murday V, Balicki M, Yee HA, Wangensteen T, Riise R, Saggar AK, Park SM, Kanuga N, Francis PJ, Maher ER, Moore AT, Russell-Eggitt IM, Hardcastle AJ. X-linked cataract and Nance-Horan syndrome are allelic disorders. Hum Mol Genet. 2009 Jul 15;18(14):2643-55.

PubMed ID: 
19414485

Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation

Burdon KP, McKay JD, Sale MM, Russell-Eggitt IM, Mackey DA, Wirth MG, Elder JE, Nicoll A, Clarke MP, FitzGerald LM, Stankovich JM, Shaw MA, Sharma S, Gajovic S, Gruss P, Ross S, Thomas P, Voss AK, Thomas T, Gecz J, Craig JE. Mutations in a novel gene, NHS, cause the pleiotropic effects of Nance-Horan syndrome, including severe congenital cataract, dental anomalies, and mental retardation. Am J Hum Genet. 2003 Nov;73(5):1120-30.

PubMed ID: 
14564667

Axenfeld-Rieger Syndrome, Type 1

Clinical Characteristics
Ocular Features: 

Axenfeld-Rieger syndrome consists of a heterogeneous group of disorders with overlapping features.  Common to all types are the presence of ocular, dental, facial, skeletal abnormalities and autosomal dominant inheritance.  Anterior chamber dysgenesis of some form is universally present and severe glaucoma occurs in 50% of patients.  This may have its onset in childhood with typical symptoms of congenital glaucoma such as photophobia, excessive tearing and corneal clouding.  Hypoplasia of the iris is common and when progressive may result in an ectopic pupil and/or pseudopolycoria.  Iris insertion and Schwalbe's line are often anteriorly displaced with iridocorneal adhesions, a pattern that leads to the inclusion of this disorder among those with iridogoniodysgenesis or anterior chamber dysgenesis.  Pupillary ectropion of the posterior pigmented layer of the iris may be seen.

There is considerable clinical overlap among conditions with iris dysgenesis.  Some patients with typical systemic features of Axenfeld-Rieger syndrome may even have typical anterior chamber features of Axenfeld-Rieger anomaly in one eye and severe iris hypoplasia resembling aniridia in the other.

Systemic Features: 

Dental anomalies and mid-facial hypoplasia secondary to underdeveloped maxillary sinuses are among the most common systemic features in type 1.  The nasal root often appears abnormally broad and the lower lip appears to protrude. The teeth are frequently small and conical in shape with wide spaces between them (diastema).  Some teeth may be missing.  The umbilicus may fail to involute normally and retains excessive, redundant skin that sometimes leads to the erroneous diagnosis of an umbilical hernia for which unnecessary surgery may be performed.  Hypospadius is frequently present while cardiac defects, sensorineural deafness, and anal stenosis are less common.

Genetics

There is clinical and genetic heterogeneity in this syndrome and precise classification of many families remains elusive without knowing the genotype.  Mutations in at least four genes are responsible and all are are responsible for phenotypes transmitted in autosomal dominant patterns.  Type 1 discussed here is caused by a mutation in the homeobox transcription factor gene, PITX2, located at 4q25-q26.  A type of iris hypoplasia (IH)/iridogoniodysgenesis (IGDS) (IRID2; 137600) disorder has been classified separately but is caused by a mutation in PITX2 as well and many cases have the same systemic features.  Mutations in the same gene have also been found in ring dermoid of the cornea (180550) and in some cases of Peters anomaly (604229).

RIEG2 (601499) is rare but a deletion of 13q14 has been reported in several cases.  Mapping in a large family with 11 affected individuals yielded a locus in the same region.  Clinical signs overlap types 1 and 3 with dental, craniofacial, and ocular features, but with hearing impairment and rare umbilical anomalies.

Mutations in the FOXC1 gene (6p25) may be responsible for RIEG3 (602482).  However, a family has been reported with a severe 'Axenfeld-Rieger phenotype' in which a digenic etiology may have been responsible: patients had mutations in both FOXC1 and PITX2

Heterozygous mutations in the PRDM5 gene (4q25-q26) have been identified in 4 members of a Pakistani family with typical features of the Axenfeld-Rieger syndrome. It is labeled type 4 Axenfeld-Rieger syndrome in this database. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The presence of glaucoma requires prompt and vigorous treatment but control is difficult with blindness too often the result.  Oral surgery may be beneficial for dental problems.  Low vision aids can be useful.

References
Article Title: 

The Rieger syndrome

Jorgenson RJ, Levin LS, Cross HE, Yoder F, Kelly TE. The Rieger syndrome. Am J Med Genet. 1978;2(3):307-18.

PubMed ID: 
263445
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