Autosomal dominant simple microphthalmos

Heterozygous GJA1 variants with ocular phenotype: Missense in domain but truncation out of domain

Purpose

Oculodentodigital dysplasia (ODDD) is a group disorder caused by GJA1 variants, of which glaucoma leading to blindness is a frequent complication of the ocular phenotype. In this study, the correlation of the GJA1 genotype with the ocular phenotype was analyzed systematically.

Methods

GJA1 variants were collected from in-house whole-exome sequencing data of 5,307 individuals. Potentially pathogenic variants (PPVs) were defined based on prediction of multiple in silico tools, related phenotypes, and previously established evidence. The characteristics of GJA1 PPVs were evaluated based on our data, gnomAD, and HGMD.

Results

In total, 21 rare variants in GJA1 were detected in 32 subjects from the study cohort. Four of the 21 variants were classified as PPVs, including two frameshift, one missense, and one in-frame deletion. The four PPVs were detected in four probands with microcornea or high hyperopia; two developed glaucoma. A systematic review of GJA1 variants in literature suggested that most heterozygous missense PPVs are located inside the connexin domain. All truncations downstream of the connexin domain are associated with autosomal dominant disease, while most truncations within the domain are associated with autosomal recessive ODDD. Ocular signs were present in 80.0% (116/145) of patients with GJA1 PPVs. Of the 116 patients, glaucoma was observed in 26.7% (31/116), among whom 77.4% (24/31) of cases occurred in patients ≥10 years old.

Conclusions

Eye abnormalities are the most common signs associated with GJA1 PPVs, and they carry a high risk of developing glaucoma. The identification of GJA1 PPVs needs further attention and clarification.

Oculodentodigital Dysplasia: A Case Report and Major Review of the Eye and Ocular Adnexa Features of 295 Reported Cases

Oculodentodigital dysplasia (ODDD) is a rare genetic disorder associated with a characteristic craniofacial profile with variable dental, limb, eye, and ocular adnexa abnormalities. We performed an extensive literature review to highlight key eye features in patients with ODDD and report a new case of a female patient with a heterozygous missense GJA1 mutation (c.65G>A, p.G22E) and clinical features consistent with the condition. Our patient presented with multiple congenital anomalies including syndactyly, microphthalmia, microcornea, retrognathia, and a small nose with hypoplastic alae and prominent columella; in addition, an omphalocele defect was present, which has not been reported in previous cases. A systematic review of the published cases to date revealed 91 literature reports of 295 individuals with ODDD. There were 73 different GJA1 mutations associated with these cases, of which the most common were the following missense mutations: c.605G>A (p.R202H) (11%), c.389T>C (p.I130T) (10%), and c.119C>T (p.A40V) (10%). Mutations most commonly affect the extracellular-1 and cytoplasmic-1 domains of connexin-43 (gene product of GJA1), predominately manifesting in microphthalmia and microcornea. The syndrome appears with an approximately equal sex ratio. The most common eye features reported among all mutations were microcornea, microphthalmia, short palpebral fissures, and glaucoma.

Novel truncation mutations in MYRF cause autosomal dominant high hyperopia mapped to 11p12-q13.3

High hyperopia is a common and severe form of refractive error. Genetic factors play important roles in the development of high hyperopia but the exact gene responsible for this condition is mostly unknown. We identified a large Chinese family with autosomal dominant high hyperopia. A genome-wide linkage scan mapped the high hyperopia to chromosome 11p12-q13.3, with maximum log of the odds scores of 4.68 at theta = 0 for D11S987. Parallel whole-exome sequencing detected a novel c.3377delG (p.Gly1126Valfs*31) heterozygous mutation in the MYRF gene within the linkage interval. Whole-exome sequencing in other 121 probands with high hyperopia identified additional novel mutations in MYRF within two other families: a de novo c.3274_3275delAG (p.Leu1093Profs*22) heterozygous mutation and a c.3194+2T>C heterozygous mutation. All three mutations are located in the C-terminal region of MYRF and are predicted to result in truncation of that portion. Two patients from two of the three families developed angle-closure glaucoma. These three mutations were present in neither the ExAC database nor our in-house whole-exome sequencing data from 3280 individuals. No other truncation mutations in MYRF were detected in the 3280 individuals. Knockdown of myrf resulted in small eye size in zebrafish. These evidence all support that truncation mutations in the C-terminal region of MYRF are responsible for autosomal dominant high hyperopia in these families. Our results may provide useful clues for further understanding the functional role of the C-terminal region of this critical myelin regulatory factor, as well as the molecular pathogenesis of high hyperopia and its associated angle-closure glaucoma.

Relative anterior microphthalmos in oculodentodigital dysplasia

Here, we report a patient with oculodentodigital dysplasia (ODDD) caused by the c. 413G>A, p.Gly138Asp mutation in the gap junction protein alpha-1 gene. The patient suffered from characteristic dysmorphic features of ODDD. Ophthalmological investigation disclosed microcornea and a shallow anterior chamber, as expected. Surprisingly, the patient had a normal axial length and moderate myopia on both eyes. To the best of our knowledge, this is the first report on ODDD associated with relative anterior microphthalmos and myopia.

Oculodentodigital dysplasia

Oculodentodigital dysplasia is a rare, autosomal dominant disorder with high penetrance and variable expressivity, caused by mutations in the connexin 43 or gap junction protein alpha-1 gene. It has been diagnosed in fewer than 300 people worldwide with an incidence of around 1 in 10 million. It affects many parts of the body, particularly eyes (oculo), teeth (dento), and fingers and/or toes (digital). The common clinical features include facial dysmorphism with thin nose, microphthalmia, syndactyly, tooth anomalies such as enamel hypoplasia, anodontia, microdontia, early tooth loss and conductive deafness. Other less common features are abnormalities of the skin and its appendages, such as brittle nails, sparse hair, and neurological abnormalities. To prevent this syndrome from being overlooked, awareness of possible symptoms is necessary. Early recognition can prevent blindness, dental problems and learning disabilities. Described here is the case of a 21-year-old male who presented to the ophthalmology outpatient department with a complaint of bilateral progressive loss of vision since childhood.

Loss of Zebrafish Mfrp Causes Nanophthalmia, Hyperopia, and Accumulation of Subretinal Macrophages

Purpose

Mutations in membrane frizzled-related protein (MFRP) are associated with nanophthalmia, hyperopia, foveoschisis, irregular patches of RPE atrophy, and optic disc drusen in humans. Mouse mfrp mutants show retinal degeneration but no change in eye size or refractive state. The goal of this work was to generate zebrafish mutants to investigate the loss of Mfrp on eye size and refractive state, and to characterize other phenotypes observed.

Methods

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 methods were used to generate multiple frameshift mutations in zebrafish mfrp causing premature translational stops in Mfrp. Spectral-domain optical coherence tomography (SD-OCT) was used to measure eye metrics and refractive state, and immunohistochemistry was used to study adult eyes. Gene expression levels were measured using quantitative PCR.

Results

Zebrafish Mfrp was shown to localize to apical and basal regions of RPE cells, as well as the ciliary marginal zone. Loss of Mfrp in mutant zebrafish was verified histologically. Zebrafish eyes that were mfrp mutant showed reduced axial length causing hyperopia, RPE folding, and macrophages were observed subretinally. Visual acuity was reduced in mfrp mutant animals.

Conclusions

Mutation of zebrafish mfrp results in hyperopia with subretinal macrophage infiltration, phenocopying aspects of human and mouse Mfrp deficiency. These mutant zebrafish will be useful in studying the onset and progression of Mfrp-related nanophthalmia, the cues that initiate the recruitment of macrophages, and the mechanisms of Mfrp function.

High-hyperopia database, part I: clinical characterisation including morphometric (biometric) differentiation of posterior microphthalmos from nanophthalmos

PURPOSE To characterise and differentiate posterior microphthalmos (PM) and nanophthalmos (NO) using morphometric parameters.Patients and methodsConsecutive case database of patients with hyperopia >+7.00 D sphere was analysed retrospectively for clinical and biometric characterisation. Thirty-eight consecutive high-hyperopic subjects (75 eyes) with axial lengths <20.5 mm underwent uniform comprehensive ocular evaluation. Twenty-five subjects were diagnosed as PM and 13 as NO based on the horizontal corneal diameter. Parameters analysed included visual acuity, refraction, horizontal corneal diameter, anterior chamber depth, lens thickness, axial length, fundus changes, and associated ocular pathology.

PRIMARY OUTCOME MEASURES

ocular biometry difference between PM and NO.

SECONDARY OUTCOME MEASURES

differences in associated ocular pathologies between PM and NO.RESULTS Hyperopia ranged from +7 to +17 D and was similar in the two groups. Lens thickness was statistically more in NO than in PM group (4.53±0.75 mm vs 3.82±0.48 mm, P <0.001), whereas anterior chamber depth was more in the PM than in NO group (3.26±0.36 mm, vs 2.59±0.37 mm, P<0.001). NO had higher association with angle-closure glaucoma (66.7% vs 0%) and pigmentary retinopathy (38.5 vs 8.0%) but lesser association with macular folds (0% vs 24%) as compared with PM. NO was associated with poorer visual acuity.CONCLUSION PM and NO have significant differences in lens thickness, anterior chamber depth, prevalence of glaucoma, pigmentary retinopathy, macular pathology, and visual acuity while being similar in hyperopic refraction.

Novel TMEM98 mutations in pedigrees with autosomal dominant nanophthalmos

PURPOSE

Autosomal dominant nanophthalmos is an inherited eye disorder characterized by a structurally normal but smaller eye. Patients with nanophthalmos have high hyperopia (far-sightedness), a greater incidence of angle-closure glaucoma, and increased risk of surgical complications. In this study, the clinical features and the genetic basis of nanophthalmos were investigated in two large autosomal dominant nanophthalmos pedigrees.

METHODS

Fourteen members of a Caucasian pedigree from the United States and 15 members of a pedigree from the Mariana Islands enrolled in a genetic study of nanophthalmos and contributed DNA samples. Twenty of 29 family members underwent eye examinations that included measurement of axial eye length and/or refractive error. The genetic basis of nanophthalmos in the pedigrees was studied with linkage analysis, whole exome sequencing, and candidate gene (i.e., TMEM98) sequencing to identify the nanophthalmos-causing gene.

RESULTS

Nine members of the pedigree from the United States and 11 members of the pedigree from the Mariana Islands were diagnosed with nanophthalmos that is transmitted as an autosomal dominant trait. The patients with nanophthalmos had abnormally short axial eye lengths, which ranged from 15.9 to 18.4 mm. Linkage analysis of the nanophthalmos pedigree from the United States identified nine large regions of the genome (greater than 10 Mbp) that were coinherited with disease in this family. Genes within these "linked regions" were examined for disease-causing mutations using exome sequencing, and a His196Pro mutation was detected in the TMEM98 gene, which was recently reported to be a nanophthalmos gene. Sanger sequencing subsequently showed that all other members of this pedigree with nanophthalmos also carry the His196Pro TMEM98 mutation. Testing the Mariana Islands pedigree for TMEM98 mutations identified a 34 bp heterozygous deletion that spans the 3' end of exon 4 in all affected family members. Neither TMEM98 mutation was detected in public exome sequence databases.

CONCLUSIONS

A recent report identified a single TMEM98 missense mutation in a nanophthalmos pedigree. Our discovery of two additional TMEM98 mutations confirms the important role of the gene in the pathogenesis of autosomal dominant nanophthalmos.

Yeast two-hybrid analysis of a human trabecular meshwork cDNA library identified EFEMP2 as a novel PITX2 interacting protein

PURPOSE

Mutations in the homeobox transcription factor paired-like homeodomain transcription factor 2 (PITX2) cause Axenfeld-Reiger syndrome (ARS), which is associated with anterior segment dysgenesis (ASD) and glaucoma. To understand ARS pathogenesis, it is essential to know the normal functions of PITX2 and the proteins with which PITX2 interacts in the eye. Therefore, we used a unique cDNA library that we created from human trabecular meshwork (TM) primary cells to discover PITX2-interacting proteins (PIPs).

METHODS

A human TM cDNA library was created from primary cells in the ProQuest Two-Hybrid prey vector: pEXP-AD502. Human PITX2A and PITX2C isoforms were used independently as "bait" to identify novel PIPs. A total of 1.25×10⁶ clones were screened by yeast two-hybrid (Y2H) analyses. PIPs obtained from each Y2H experiment were confirmed by yeast retransformation and mammalian co-immunoprecipitation assays.

RESULTS

EGF-containing fibulin-like extracellular matrix protein 2 (EFEMP2) was identified by both PITX2A and PITX2C isoforms as a novel PIP from Y2H analyses. EFEMP2 is 443 amino acids long with six epidermal growth factor (EGF)-like modules and one fibulin-like module. The PITX2-interaction domain in EFEMP2 lies between the second EGF-like module and the COOH-terminal fibulin-like module. Co-immunoprecipitation assays in COS-7 cells confirmed the interaction between PITX2 and EFEMP2.

CONCLUSIONS

We discovered EFEMP2 as a novel PITX2-interacting protein. Further, our cDNA library made from human TM primary cells is a unique and effective resource to identify novel interacting proteins for glaucoma and ASD candidates. This resource could be used both for discovery and validation of interactomes identified from in silico analysis.

Cataract surgery in eyes with nanophthalmos and relative anterior microphthalmos

PURPOSE

To compare the refractive outcome and postoperative complications of cataract surgery among nanophthalmos and relative anterior microphthalmos and the normal control eyes.

DESIGN

Retrospective case-control series.

METHODS

Seventeen eyes with nanophthalmos, 29 eyes with relative anterior microphthalmos, and 54 normal control eyes were enrolled in this study. The subjects were divided into 3 diagnostic subgroups according to the following: nanophthalmos with an axial length <20.5 mm and without morphologic malformation; relative anterior microphthalmos with a corneal diameter (CD) ≤ 11 mm, an anterior chamber depth (ACD) ≤ 2.2 mm, and an axial length (AL) ≥ 20.5 mm; and normal control group eyes defined as an AL ≥ 20.5 mm with a CD >11 mm or an ACD >2.2 mm. The implanted intraocular lens (IOL) power was used to calculate the predicted postoperative refraction error according to 4 IOL power formulas: SRK II, SRK/T, Hoffer Q, and Holladay 1. With each formula, the mean numeric error and mean absolute error were calculated. At postoperative 2 months, the endothelial cell count and the complications were analyzed.

RESULTS

As measured by mean numeric error or mean absolute error, there was a significant difference among the 3 groups based on SRK II, SRK/T, and Hoffer Q, with less predictability in the nanophthalmic eyes. In eyes with nanophthalmos, the Holladay 1 produced the best refractive results as measured by mean numeric error (P < .001). A higher occurrence rate of posterior capsule rupture (11.7%) was shown in the nanophthalmic eyes. The difference among the 3 groups for the postoperative endothelial cell loss was not significant (P = .421).

CONCLUSIONS

The refractive predictability and postoperative outcome was poorer in the eyes with nanophthalmos compared to the eyes with relative anterior microphthalmos or normal control.

Chronic central serous choroidopathy with severe visual loss in hyperopic microphthalmic identical twins

OBJECTIVE

To report chronic central serous choroidopathy with severe visual loss in hyperopic microphthalmic identical twins.

METHODS

The index patient was first examined in 1994, at age 31, and has been followed up closely for 17 years. He had repeated fluorescein and indocyanine green angiograms, OCT, ultrasound biometry, and recently also autofluorescence and EDI OCT. His twin brother was first examined in 2010, at age 47, and had a similar extensive exploration.

RESULTS

The index patient had a mean refractive error of +6 D OU and VA was 20/32++ in the RE and 20/200 in the LE in 1994. Vision slowly went down to 20/800+ in the RE and 20/600 in the LE in 2011. His twin brother has a mean refractive error of +6 D OU and VA 20/400 OU. Both have a short axial length of the eye, a thick choroid with dilated vessels, and central serous choroidopathy with cystic degeneration of the macula and retina in the posterior pole.

CONCLUSIONS

We add to the reported complications of microphthalmos, chronic central serous choroidopathy.

Gap junctions in inherited human disease

Gap junctions (GJ) provide direct intercellular communication. The structures underlying these cell junctions are membrane-associated channels composed of six integral membrane connexin (Cx) proteins, which can form communicating channels connecting the cytoplasms of adjacent cells. This provides coupled cells with a direct pathway for sharing ions, nutrients, or small metabolites to establish electrical coupling or balancing metabolites in various tissues. Genetic approaches have uncovered a still growing number of mutations in Cxs related to human diseases including deafness, skin disease, peripheral and central neuropathies, cataracts, or cardiovascular dysfunctions. The discovery of a growing number of inherited human disorders provides an unequivocal demonstration that gap junctional communication is crucial for diverse physiological processes.

Compound heterozygosity for a novel and a recurrent MFRP gene mutation in a family with the nanophthalmos-retinitis pigmentosa complex

PURPOSE

To report a new familial case of the recently described autosomal recessive syndrome of nanophthalmos-retinitis pigmentosa-foveoschisis-optic disc drusen, which arises from compound heterozygosity for Membrane Frizzled-Related Protein (MFRP) mutations in a sibling pair of Mexican origin.

METHODS

Ophthalmological assessment included slit-lamp and dilated fundus examination, applanation tonometry, fundus photography, A-mode and B-mode ultrasound examination, electroretinogram, fluorescein retinal angiography, optical coherence tomography, and electrooculogram in both affected siblings. Molecular genetic analysis consisted of PCR amplification and direct automated sequence of the complete coding region of the MFRP gene. In addition, allele-specific cloning and sequencing techniques were used to characterize a heterozygous MFRP frameshift mutation.

RESULTS

Clinical examination revealed high hyperopia of > +16 diopters while electroretinographic and fluorangiographic studies demonstrated a retinal dystrophy compatible with retinitis pigmentosa. Ultrasound examination showed nanophthalmos (eye axial length <15 mm) and optic disc drusen while optical coherence tomography evidenced cystoid macular edema. Nucleotide sequencing in DNA from both affected siblings disclosed the presence of two MFRP mutations: a novel heterozygous point mutation predicting a nonsense change from tyrosine (TAC) to a stop signal (TAA) at codon 317, and a heterozygous 1 bp deletion in exon 5, predicting a prematurely truncated protein (p.Asn167ThrfsX25).

DISCUSSION

The third known family with the syndrome of nanophthalmos-retinitis pigmentosa-foveoschisis-optic disc drusen is presented. This is the first demonstration of compound heterozygosity for MFRP mutations as the source of the disease. The affected siblings described here are the youngest patients with the disease reported to date and the comparison of their clinical data with previous individuals with this syndrome suggest that some aspects of the phenotype are probably age-dependent.

GJA1 mutations, variants, and connexin 43 dysfunction as it relates to the oculodentodigital dysplasia phenotype

The predominantly autosomal dominant disorder, oculodentodigital dysplasia (ODDD) has high penetrance with intra- and interfamilial phenotypic variability. Abnormalities observed in ODDD affect the eye, dentition, and digits of the hands and feet. Patients present with a characteristic facial appearance, narrow nose, and hypoplastic alae nasi. Neurological problems, including dysarthria, neurogenic bladder disturbances, spastic paraparesis, ataxia, anterior tibial muscle weakness, and seizures, are known to occur as well as conductive hearing loss, cardiac defects, and anomalies of the skin, hair, and nails. In 2003, our analysis of 17 ODDD families revealed that each had a different mutation within the human gap junction alpha 1 (GJA1) gene which encodes the protein connexin 43 (Cx43). Since then at least 17 publications have identified an additional 26 GJA1 mutations and in this study, we present 28 new cases with 18 novel GJA1 mutations. We include tables summarizing the 62 known GJA1 nucleotide changes leading to Cx43 protein alterations and the phenotypic information available on 177 affected individuals from 54 genotyped families. Mutations resulting in ODDD occur in each of the nine domains of the Cx43 protein, and we review our functional experiments and those in the literature, examining the effects of 13 different Cx43 mutations upon gap junction activity.

Hereditary High Hypermetropia in the Faroe Islands

PURPOSE

To characterize the phenotype of two families with high hypermetropia from the Faroe Islands.

METHODS

Ophthalmologic evaluation including ultrasound oculometry and anthropometric measurements.

RESULTS

Of the 40 examined family members, 15 individuals (8 males, 7 females; ages: 6-77 years; mean: 36.5 years) had small deep-set eyes with high hypermetropia (median: + 16.5 D; range: + 7.75 to + 22), short axial eye length (< 21 mm), and a thickened eye wall. The median corrected visual acuity was 0.4 (0.2-0.9). Ocular complications included angle-closure glaucoma in six eyes, uveal effusion in three eyes, cataract in two eyes, and esotropia with amblyopia in three eyes. An emergency case of uveal effusion and retinal detachment after Yag iridotomy eventually responded to systemic corticosteroids and scleral resection surgery with a slow visual recovery. No associated ocular or systemic malformations were found in the series. In addition to the two examined families, six smaller Faroese families with high hypermetropia are briefly reported.

CONCLUSIONS

The study highlights the signs and symptoms of a rare hereditary phenotype characterized by a short axial length mainly confined to the posterior segment of the eye, a shallow anterior chamber, and a thickened eye wall. The morphological characteristics predispose for sight-threatening complications such as angle-closure glaucoma, chorioretinal pathology including uveal effusion, and amblyopia. Regular ophthalmic follow-up is therefore of obvious importance in families known to have small eyes/high hypermetropia. An endemic high prevalence in the Faroe Islands suggests the presence of a founder effect, and further genetic research would probably indicate pseudodominant rather than dominant transmission

Unilateral Isolated Microphthalmia Inherited as an Autosomal Recessive Trait

PURPOSE

To report a family with unilateral isolated microphthalmia showing an autosomal recessive pattern of inheritance.

CASE REPORT

We report a family in which three out of four children, one male and monozygotic female twins, were born with unilateral isolated microphthalmia to healthy consanguineous parents. One twin additionally had a horseshoe kidney. Rare cases of familial isolated microphthalmia/anophthalmia have been previously described. This is the first report of a family with autosomal recessive isolated microphthalmia occurring unilaterally in all affected individuals. It remains unknown how this inherited genetic disease results in unilateral manifestation.

CONCLUSION

Mirror imaging of this condition in the monozygotic twins may help elucidate the underlying mechanism. The constellation of features in this family may contribute to solve remaining questions of research into symmetry and asymmetry.

A genome-wide linkage scan in Tunisian families identifies a novel locus for non-syndromic posterior microphthalmia to chromosome 2q37.1

Posterior microphthalmia (PM) is a relatively rare autosomal recessive condition with normal anterior segment and small posterior segment resulting in high hyperopia and retinal folding. It is an uncommon subtype of microphthalmia that has been mostly reported to coexist with several other ophthalmic conditions and to occur in sporadic cases. The membrane-type frizzled-related protein (MFRP) is the only gene so far reported implicated in autosomal recessive, non-syndromic and syndromic forms of PM. Here, we performed a clinical and genetic analysis using six consanguineous families ascertained from different regions of Tunisia and affected with non-syndromic PM that segregates as an autosomal recessive trait. To identify the disease-causing defect in these families, we first analysed MFRP gene, then some candidate genes (CHX10, OPA1, MITF, SOX2, CRYBB1-3 and CRYBA4) and loci (MCOP1, NNO1 and NNO2) previously implicated in different forms of microphthalmia. After exclusion of these genes and loci, we performed a genome-wide scan using a high density single nucleotide polymorphism (SNP) array 50 K in a large consanguineous pedigree. SNP genotyping revealed eight homozygous candidate regions on chromosomes 1, 2, 3, 6, 15, 17 and 21. Linkage analysis with additional microsatellite markers only retained the 2q37.1 region with a maximum LOD score of 8.85 obtained for D2S2344 at theta = 0.00. Further investigations are compatible for linkage of four more families to this region with a refined critical interval of 2.35 Mb. The screening of five candidate genes SAG, PDE6D, CHRND, CHRNG and IRK13 did not reveal any disease-causing mutation.

Localization of a novel gene for congenital nonsyndromic simple microphthalmia to chromosome 2q11-14

Microphthalmia is a clinically and genetically heterogeneous disorder of eye development. The genetic basis of nonsyndromic microphthalmia is not yet fully understood. Previous studies indicated that disease pedigrees from different genetic backgrounds could be attributed to completely different gene loci. To investigate the etiology in a large autosomal-dominant inherited simple microphthalmia (nanophthalmia) pedigree, which is the first genetically analyzed Chinese microphthalmia pedigree, we performed a whole-genome scan using 382 micro-satellite DNA markers after the exclusion of reported candidates associated with microphthalmia. Strong evidence indicated that microphthalmia in this family was mapped to an unreported new locus on chromosome 2q. A significantly positive two-point LOD score was obtained with a maximum 3.290 at a recombination fraction of 0.00 for marker D2S2265. Subsequent haplotype analysis and recombination data further confined the disease-causing gene to a 15-cM interval between D2S1890 and D2S347 on 2q11-14. Our results further underlined the degree of heterogeneity in microphthalmia from Chinese background and localized a novel gene which regulates eye embryogenesis.

Pervasive ocular anomalies in posterior microphthalmos

BACKGROUND

Posterior microphthalmos is a relatively rare condition that has been reported to coexist with several other ophthalmic conditions. However, to the best of the authors' knowledge, there are no previous reports that have found posterior microphthalmos and refractive, binocular, retinal, and neurologic considerations, along with a possible hereditary component. The following report documents the coexistence of posterior microphthalmos with severe hyperopia, esotropia, macular folds, and optic nerve hypoplasia in a pair of siblings.

CASE REPORT

A 9-year-old Hispanic girl presented for a comprehensive eye examination. Best-corrected visual acuity (VA) was reduced in both eyes with poorer VA in the right eye. Binocular testing found a small angle constant right esotropia (ET). On dilated fundus examination, a peculiar, elevated, dolphin-shaped folding of the macula was identified, the right eye greater than the left eye, that extended toward an anomalous optic nerve head in both eyes (OU), presumed to be a disc hypoplasia. The patient's brother, who also exhibited severe hyperopia and ET, presented with a similar acuity reduction, a nearly identical folded macular appearance, the right eye more so than the left eye, and a probable optic nerve hypoplasia. Pachymetry, ultrasonography, and ocular coherence tomography imaging of both siblings found thickened corneas in the presence of posterior microphthalmos OU and macular folds affecting only the retina, leaving the choroid and sclera unaffected.

CONCLUSIONS

Posterior microphthalmos may exist in the presence of ocular anomalies along with refractive, binocular, retinal, neurologic, and genetic considerations. In this case, optical coherence tomography provided information on the internal morphology of the macular folds, which helped direct the differential diagnosis. The similar presentation among siblings supports a hereditary component that warrants further investigation.

A population-based case-control study of isolated anophthalmia and microphthalmia

The purpose of the study was to reveal the etiological factors in the origin of isolated an/microphthalmia. The dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-2002 containing 56 cases with isolated an/microphthalmia and 22,744 malformed controls with other non-ocular defects from the Hungarian Congenital Abnormality Registry, in addition of 56 matched control pairs and 37,837 population controls without defects from the National Birth Registry, was evaluated. Exposure data and family history were collected (i) prospectively by prenatal logbook and other medical records, (ii) retrospectively through a structured questionnaire filled-in by mothers, and (iii) information obtained by regional nurses at home visit of non-respondent mothers. The autosomal recessive origin of isolated an/microphthalmia was indicated in about 10% of cases on the basis of sib recurrence. Cases with isolated an/microphthalmia had a much shorter mean gestational age and smaller mean birth weight, a much larger proportion of preterm birth and low birthweight. Their mothers were younger with a predominance of first birth order, frequently unmarried with low socioeconomic status. These findings are in agreement with a much higher prevalence at birth of cases with isolated an/microphthalmia in the gypsy population probably due to the interaction of inbreeding effect and low socioeconomic status. Further molecular genetic studies are needed to identify gene mutations of isolated an/microphthalmia in the Hungarian gypsy population.

A novel GJA1 mutation causes oculodentodigital dysplasia without syndactyly

Oculodentodigital dysplasia (ODDD) is a rare autosomal dominant pleiotropic disorder, caused by mutations in the Connexin 43 gene (GJA1) [Paznekas et al. (2003): Am J Hum Genet 72:408-418], which is localized to human chromosome 6q22-q23. Here, we describe the identification of a novel heterozygous missense mutation in the GJA1 gene, (H194P) in an Italian family previously reported to be affected by isolated autosomal dominant microphthalmia [Vingolo et al. (1994): J Med Genet 31:721-725]. Careful clinical re-evaluation revealed that this family shows an atypical form of ODDD, characterized by the predominance of the ocular involvement and by the absence of hand and/or foot syndactyly. The mutation affects an amino acid residue localized in the second extracellular domain of the Cx43 protein and highly conserved across evolution. This finding confirms the highly variable phenotypic expression caused by GJA1 mutations.

Oculometric Characteristics of Extreme Hypermetropia in Two Faroese Families

PURPOSE

To describe and analyze the oculometric features of small eyes with high hypermetropia in two Faroese families, with emphasis on refractive components.

METHODS

Members of the two families (N=40; age, 1 to 77 years), including 15 cases of extreme hypermetropia (+7.5 to +19.25 D), had an ophthalmic evaluation including refractometry, keratometry, and axial ocular measurements using A-scan ultrasound. Eye-wall thickness was assessed using B-scan. Nonparametric statistics were used, mainly the Mann-Whitney U test.

RESULTS

In the two families, there were six and nine probands, respectively, with hypermetropia more than +7 D and short eyes as defined by axial eye lengths <21 mm. The median corrected visual acuity was 0.4 (range, 0.2 to 0.9). Gross fundus abnormalities were not observed. All 15 had a short posterior segment with a thick eye wall and a relatively thick lens. Furthermore, steep and rather small corneas were present. In one of the families, 70% of the affected had a corneal curvature radius of < or =7.0 mm. Five probands from family 2 were labeled as possibly affected because of hypermetropia and borderline axial length findings (21 to 22 mm). The remaining 20 subjects had visual acuity and oculometric findings within physiologic limits.

CONCLUSIONS

The axial measurement features in our series of highly hypermetropic eyes mainly presented as an extension downward from the hypermetropic bottom line of the normal distribution. The axial shortness of the eyes was primarily the result of a short posterior eye segment ("posterior microphthalmos"). A steep cornea was a feature in most small eyes in our series, particularly in one family branch.

Heritable unilateral clinical anophthalmia

We examined a newborn child with unilateral right-sided clinical anophthalmos born to a mother with unilateral left-sided anophthalmos. Although rare, isolated nonsyndromic heritable unilateral anophthalmia and microphthalmia have been reported in the literature. We briefly review the genetics of such anomalies and discuss the importance of a full clinical genetics evaluation. Treatment of this patient's anophthalmic socket consists of progressive conformer expansion to be followed by placement of a self-inflating polymer expander.

Cataract surgery in patients with nanophthalmos

PURPOSE

To evaluate the results and complications of cataract surgery in patients with nanophthalmos.

SETTING

University hospital practice.

METHODS

The records of consecutive patients with nanophthalmos who had cataract surgery from 1978 through 2002 were reviewed for ocular diagnoses, corneal diameter, keratometry, axial length, retinal-choroidal-scleral thickness determined by echography, ocular surgeries, visual acuity, and complications.

RESULTS

Eight patients (6 women, 2 men) with a mean age of 59 years were reviewed. Four patients were not previously diagnosed with nanophthalmos; increased retinal-choroidal-scleral thickness (mean 2.41 mm) confirmed the diagnosis. Twelve eyes had cataract extraction with posterior chamber intraocular lens (IOL) implantation, 11 by phacoemulsification and 1 by extracapsular cataract extraction, and 4 eyes had lamellar scleral resections. Additional surgeries included glaucoma laser treatment (8 eyes), cyclocryotherapy (2 eyes), trabeculectomy with scleral resection (1 eye), trabeculectomy combined with phacoemulsification (1 eye), and neodymium:YAG laser capsulotomy (4 eyes). No eye lost vision; however, complications included severe iritis, broken IOL haptic with vitreous loss, posterior capsule opacity, choroidal hemorrhage, phthisis, and aqueous misdirection.

CONCLUSIONS

Results indicate that echography should be used to assess retinal-choroidal-scleral thickness in eyes that are hyperopic and at risk for narrow-angle glaucoma. Thickening may confirm the diagnosis of nanophthalmos and allow careful preoperative assessment and appropriate operative procedures in these high-risk eyes. With advances in cataract, glaucoma, and uveal effusion treatments, surgical results in patients with nanophthalmos are improving.

Colobomatous macrophthalmia with microcornea syndrome: report of a new pedigree

Colobomatous macrophthalmia with microcornea syndrome (MIM 602499) is a very rare eye malformation. To date, only two families with a total number of eight patients have been reported. We report on 13 additional cases in a single three-generation family and describe the eye findings and quantitative parameters of corneal curvature and axial ocular dimensions. All affected relatives had bilateral involvement with typical inferonasal iris coloboma, chorioretinal coloboma, microcornea, and varying degrees of axial enlargement associated with myopia. Additional findings included flatter corneal curvatures and shallower anterior chambers. Iridocorneal angle abnormalities associated with elevation of intraocular pressure were detected in three patients. The pedigree confirms the autosomal dominant pattern of inheritance with complete penetrance.

Posterior segment changes associated with posterior microphthalmos

PURPOSE

To characterize and analyze the posterior segment ocular involvement in patients with posterior microphthalmos.

DESIGN

Retrospective observational case series.

PARTICIPANTS

Eighteen patients (8 sporadic cases and 10 siblings from 5 different families) between the age of 4 and 36 years with posterior microphthalmos.

METHODS

Records of patients with posterior microphthalmos over a 5-year-period were reviewed, including clinical, fundus photographic, fluorescein angiographic, and ultrasonographic findings, and management.

RESULTS

All patients had bilateral foreshortening of the posterior ocular segment (range, 7--11.2 mm) with associated high hyperopia (range, +12.00--+19.00 diopters) and normal or slightly smaller than normal anterior segment dimensions. Visual acuity ranged from 20/200 to 20/40. Inheritance of this syndrome was compatible with an autosomal recessive pattern. Posterior segment changes included bilateral elevated papillomacular retinal fold (13 patients, 72.2%); fine retinal folds (6 patients, 33.3%); chorioretinal folds (11 patients, 61.1%); uveal effusion syndrome (3 patients, 16.7%); pigmentary retinopathy (4 patients, 22.2%), including retinitis punctata albescens in 1 patient; absence or marked reduction of the capillary-free zone (18 patients, 100%); crowded optic discs (18 patients, 100%); and sclerochoroidal thickening on ultrasonography (18 patients, 100%). Two patients with uveal effusion were successfully treated with scleral surgery.

CONCLUSION

A wide variety of congenital or acquired posterior segment changes may be encountered in patients with posterior microphthalmos. Although high hyperopia and elevated papillomacular retinal fold are the main causes of visual impairment, other chorioretinal changes, such as pigmentary retinopathy, chorioretinal folds and uveal effusion syndrome, should be considered as causes of visual disturbance in patients with posterior microphthalmos. Early ultrasonographic diagnosis, close follow-up, and appropriate management are mandatory to improve or maintain visual function in such patients.

A locus for autosomal dominant colobomatous microphthalmia maps to chromosome 15q12-q15

Congenital microphthalmia is a common developmental ocular disorder characterized by shortened axial length. Isolated microphthalmia is clinically and genetically heterogeneous and may be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. Here, we studied a five-generation family of Sephardic Jewish origin that included 38 members, of whom 7 have either unilateral or bilateral microphthalmia of variable severity inherited as an autosomal dominant trait with incomplete penetrance. After exclusion of several candidate loci, we performed a genome-scan study and demonstrated linkage to chromosome 15q12-q15. Positive LOD scores were obtained with a maximum at the D15S1007 locus (maximum LOD score 3.77, at recombination fraction 0.00). Haplotype analyses supported the location of the disease-causing gene in a 13.8-cM interval between loci D15S1002 and D15S1040.

Phenotype of autosomal recessive congenital microphthalmia mapping to chromosome 14q32

BACKGROUND

Congenital microphthalmia (OMIM: 309700) may occur in isolation or in association with a variety of systemic malformations. Isolated microphthalmia may be inherited as an autosomal dominant, an autosomal recessive, or an X linked trait.

METHODS

Based on a whole genome linkage analysis, in a six generation consanguineous family with autosomal recessive inheritance, the first locus for isolated microphthalmia was mapped to chromosome 14q32. Eight members of this family underwent clinical examination to determine the nature of the microphthalmia phenotype associated with this locus.

RESULTS

All affected individuals in this family suffered from bilateral microphthalmia in association with anterior segment abnormalities, and the best visual acuity achieved was "perception of light". Corneal changes included partial or complete congenital sclerocornea, and the later development of corneal vascularisation and anterior staphyloma. Intraocular pressure, as measured by Schiotz tonometry, was greatly elevated in many cases.

CONCLUSIONS

This combination of ocular defects suggests an embryological disorder involving tissues derived from both the neuroectoderm and neural crest. Other families with defects in the microphthalmia gene located on 14q32 may have a similar ocular phenotype aiding their identification.

Autosomal dominant nanophthalmos (NNO1) with high hyperopia and angle-closure glaucoma maps to chromosome 11

Nanophthalmos is an uncommon developmental ocular disorder characterized by a small eye, as indicated by short axial length, high hyperopia (severe farsightedness), high lens/eye volume ratio, and a high incidence of angle-closure glaucoma. We performed clinical and genetic evaluations of members of a large family in which nanophthalmos is transmitted in an autosomal dominant manner. Ocular examinations of 22 affected family members revealed high hyperopia (range +7.25-+13.00 diopters; mean +9.88 diopters) and short axial length (range 17.55-19.28 mm; mean 18.13 mm). Twelve affected family members had angle-closure glaucoma or occludable anterior-chamber angles. Linkage analysis of a genome scan demonstrated highly significant evidence that nanophthalmos in this family is the result of a defect in a previously unidentified locus (NNO1) on chromosome 11. The gene was localized to a 14.7-cM interval between D11S905 and D11S987, with a maximum LOD score of 5. 92 at a recombination fraction of .00 for marker D11S903 and a multipoint maximum LOD score of 6.31 for marker D11S1313. NNO1 is the first human locus associated with nanophthalmos or with an angle-closure glaucoma phenotype, and the identification of the NNO1 locus is the first step toward the cloning of the gene. A cloned copy of the gene will enable examination of the relationship, if any, between nanophthalmos and less severe forms of hyperopia and between nanophthalmos and other conditions in which angle-closure glaucoma is a feature.

A locus for autosomal recessive congenital microphthalmia maps to chromosome 14q32

Congenital microphthalmia (CMIC) (OMIM 309700) may occur in isolation or in association with a variety of systemic malformations. Isolated CMIC may be inherited as an autosomal dominant, an autosomal recessive, or an X-linked trait. On the basis of a whole-genome linkage analysis, we have mapped the first locus for isolated CMIC, in a five-generation consanguineous family with autosomal recessive inheritance, to chromosome 14q32. All affected individuals in this family have bilateral CMIC. Linkage analysis gave a maximum two-point LOD score of 3.55 for the marker D14S65. Surrounding this marker is a region of homozygosity of 7.3 cM, between the markers D14S987 and D14S267, within which the disease gene is predicted to lie. The genes for several eye-specific transcription factors are located on human chromosome 14q and in the syntenic region of mouse chromosome 12. However, both CHX10 (14q24.3), mutations of which give rise to CMIC in mouse models, and OTX2 (14q21-22) can be excluded as candidates for autosomal recessive congenital microphthalmia (arCMIC), since they map outside the critical disease region defined by recombination events. This suggests that arCMIC is caused by defects in a novel developmental gene that may be important or even essential in eye development.

Nanophthalmos with longstanding choroidal effusion and serous retinal detachment

PURPOSE

To report a typical case of nanophthalmos with uveal effusion and local serous retinal detachment followed for 1 year.

METHODS

Clinical ocular examinations included vision, refraction, corneal diameter, anterior chamber depth, intraocular pressure, fundoscopy, A/B scan ultrasonography and gonioscopy.

RESULTS

Both eyes were hypermetropic with small corneas and shallow anterior chambers. Decreased axial length and thickened sclera were also found. There were peripheral choroidal effusions and local serous retinal detachments as well. The patient declined any surgery that was offered. No significant change in either eye was found after 1 year follow-up.

CONCLUSION

This case illustrates that the progress of choroidal effusion and retinal detachment in nanophthalmos may be very slow and even non-progressive for at least 1 year. In these cases sclerectomy and or sclerotomy may be delayed without undue immediate risk to the vision.

Treatment of glaucoma in young nanophthalmic patients

PURPOSE

To evaluate the criteria of diagnosis and management of secondary glaucoma in young nanophthalmic patients.

METHODS

Considering the anatomic features and clinical characteristics, 22 eyes of 11 patients were identified as bilateral nanophthalmos. Intraocular pressures (IOP) were checked with Goldmann applanation or Keeler pulse-air 2000 tonometer, and Nd-Yag laser was used for iridotomies. Prophylactic V-shaped unsutured sclerectomies over the pars plana were combined with trabeculectomy, and Mitomycin C (MMC) in 0.2 mg/ml concentration was applied.

RESULTS

Among 22 eyes of bilateral nanophthalmic patients 8 eyes had secondary angle-closure glaucoma. Laser iridotomies were performed in 6 eyes. Laser iridotomy and supplemental medical therapy were sufficient in 4 out of 6 eyes. Mean IOP dropped from 26.4 to 14.5 mmHg in these patients. Due to continuous increase of IOP in the other patients, they underwent trabeculectomy with V-shaped sclerostomy and intraoperative MMC application. Mean IOP dropped from 39.3 mmHg to 19.3 mmHg. Postoperative uveal effusion on other major complications were not observed. Mean age of these patients was 14.6 years during treatment.

CONCLUSION

Management of glaucoma in nanophthalmus is complicated. Initial treatment is medical. If it is insufficient, laser iridotomies and V-shaped sclerostomies with filtration surgery can be performed at any age.

Autosomal dominant simple microphthalmos: incomplete penetrance and variable expression in a large family

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