Histologic phenotype-genotype correlation of corneal dystrophies associated with eight distinct mutations in the TGFBI gene

Clinical and Histopathologic Characteristics and Template of the TGFBI p.(His626Arg) Missense Variant Lattice Corneal Dystrophy

PURPOSE

The aim of this study was to define, following the IC3D template format, the clinical and histopathologic phenotype of the p.(His626Arg) missense variant lattice corneal dystrophy (LCDV-H626R), the most common variant lattice dystrophy, and to record long-term outcome of corneal transplantation in this dystrophy.

METHODS

A database search and a meta-analysis of published data on LCDV-H626R were conducted. A patient diagnosed with LCDV-H626R who underwent bilateral lamellar keratoplasty followed by rekeratoplasty of 1 eye is described, including histopathologic examination of the 3 keratoplasty specimens.

RESULTS

One hundred forty-five patients from at least 61 families and 11 countries diagnosed with LCDV-H626R were found. This dystrophy is characterized by recurrent erosions, asymmetric progression, and thick lattice lines that extend to corneal periphery. The median age is 37 (range, 25-59) years at the onset of symptoms, 45 (range, 26-62) years at the time of diagnosis, and 50 (range, 41-78) years at the time of the first keratoplasty, suggesting a median interval from the first symptoms to diagnosis and to keratoplasty of 7 and 12 years, respectively. Clinically unaffected carriers have been of age 6 to 45 years. Central anterior stromal haze and centrally thick, peripherally thinner branching lattice lines in the anterior to midstroma of the cornea were noted preoperatively. Histopathology of the host anterior corneal lamella showed a subepithelial fibrous pannus, a destroyed Bowman layer, and amyloid deposits extending to the deep stroma. In the rekeratoplasty specimen, amyloid localized to scarring along the Bowman membrane and to the margins of the graft.

CONCLUSIONS

The IC3D-type template for LCDV-H626R should help diagnose and manage variant carriers. The histopathologic spectrum of findings is broader and more nuanced than what has been reported.

Bilateral reticular haze and scar involving central cornea

A 17-year-old girl with a few years' history of declining vision, photophobia, and dry eye symptoms was referred to our clinic. She noted that the vision in the right eye declined significantly over the past several months. On her last year examination, her uncorrected distance visual acuity (UDVA) was recorded as 20/25 in both eyes with a corrected distance visual acuity (CDVA) of 20/20 in both eyes with minimal refractive error, with a diagnosis of bilateral Salzmann nodular degeneration. The patient was given artificial tears and was encouraged to wear sunglasses. On examination now, UDVA was 20/70 in the right eye and 20/40 in the left eye. The manifest refraction was -2.00 + 1.25 × 96 in the right eye and -1.00 + 2.00× 34 in the left eye, with a CDVA of 20/50 and 20/30, respectively. Slitlamp examination revealed superficial reticular stromal scar with clear intervening spaces involving the anterior 75 μm of the stromal cornea in the central 6.0 mm optical zone (Figure 1).JOURNAL/jcrs/04.03/02158034-202104000-00021/figure1/v/2021-04-19T183640Z/r/image-tiffJOURNAL/jcrs/04.03/02158034-202104000-00021/figure2/v/2021-04-19T183640Z/r/image-tiff The rest of the anterior and posterior segment examination was completely normal and noncontributory. Anterior segment optical coherence tomography (AS-OCT) revealed subepithelial lesion involving the central aspect of the cornea in the right eye more than that in the left eye (Figure 2). Family history was significant for an older sister with a similar problem who never required medical attention. She also has mild photophobia and dry eye symptoms. What is your differential diagnosis? What diagnostic test will help you in your diagnosis and clinical decision-making? What is the most likely diagnosis in this case? Do you recommend medical and/or surgical intervention in the right eye, realizing that there has been exacerbation of her ocular condition in the most recent year? What is the long-term prognosis and future plan for a patient with this potential condition?

Structural and Functional Implications of Human Transforming Growth Factor β-Induced Protein, TGFBIp, in Corneal Dystrophies

A major cause of visual impairment, corneal dystrophies result from accumulation of protein deposits in the cornea. One of the proteins involved is transforming growth factor β-induced protein (TGFBIp), an extracellular matrix component that interacts with integrins but also produces corneal deposits when mutated. Human TGFBIp is a multi-domain 683-residue protein, which contains one CROPT domain and four FAS1 domains. Its structure spans ∼120 Å and reveals that vicinal domains FAS1-1/FAS1-2 and FAS1-3/FAS1-4 tightly interact in an equivalent manner. The FAS1 domains are sandwiches of two orthogonal four-stranded β sheets decorated with two three-helix insertions. The N-terminal FAS1 dimer forms a compact moiety with the structurally novel CROPT domain, which is a five-stranded all-β cysteine-knot solely found in TGFBIp and periostin. The overall TGFBIp architecture discloses regions for integrin binding and that most dystrophic mutations cluster at both molecule ends, within domains FAS1-1 and FAS1-4.

Pathogenesis and treatments of TGFBI corneal dystrophies

Transforming growth factor beta-induced (TGFBI) corneal dystrophies are a group of inherited progressive corneal diseases. Accumulation of transforming growth factor beta-induced protein (TGFBIp) is involved in the pathogenesis of TGFBI corneal dystrophies; however, the exact molecular mechanisms are not fully elucidated. In this review article, we summarize the current knowledge of TGFBI corneal dystrophies including clinical manifestations, epidemiology, most common and recently reported associated mutations for each disease, and treatment modalities. We review our current understanding of the molecular mechanisms of granular corneal dystrophy type 2 (GCD2) and studies of other TGFBI corneal dystrophies. In GCD2 corneal fibroblasts, alterations of morphological characteristics of corneal fibroblasts, increased susceptibility to intracellular oxidative stress, dysfunctional and fragmented mitochondria, defective autophagy, and alterations of cell cycle were observed. Other studies of mutated TGFBIp show changes in conformational structure, stability and proteolytic properties in lattice and granular corneal dystrophies. Future research should be directed toward elucidation of the biochemical mechanism of deposit formation, the relationship between the mutated TGFBIp and the other materials in the extracellular matrix, and the development of gene therapy and pharmaceutical agents.

A novel phenotype-genotype correlation with an Arg555Trp mutation of TGFBI gene in Thiel-Behnke corneal dystrophy in a Chinese pedigree

Background

To investigate the molecular defects in a four-generation Chinese pedigree affected with Thiel-Behnke corneal dystrophy (TBCD). And to further study the relationship between genetic mutation and clinical manifestations.

Methods

Individuals of the pedigree were recruited for extensive ophthalmic examinations. Histological studies of two corneal buttons obtained from lamellar keratoplasty were conducted. Peripheral blood was collected in EDTA for genomic DNA isolation from leukocytes of all affected and unaffected members. All 17 exons of the TGFBI gene were screened for mutations by polymerase chain reaction and direct DNA sequencing.

Results

Clinical examinations revealed a typical pattern of honeycomb-like TBCD. Histopathology study demonstrated eosinophilic deposits that were congo-red-positive and did not stain with periodic acid Schiff or Masson’s trichrome. Genetic analysis disclosed a heterozygous p. Arg555Trp mutation resulted from a missense c. 1663C > T nucleotide change in exon 12 of TGFBI gene in all affected members. Morever, a second rare variant in exon 6 of the TGFBI gene (p. Arg257Trp) also cosegregated within this family and has been confirmed to be a single nucleotide polymorphism (SNP) not previously reported.

Conclusions

The p. Arg555Trp mutation of the TGFBI gene was associated with TBCD, which revealed a novel phenotype-genotype correlation within the mutational spectrum of phenotypically diverse corneal dystrophies.

Confocal microscopy and optical coherence tomography imaging of hereditary granular dystrophy

OBJECTIVES

This case report examines the clinical characteristics of hereditary granular dystrophy through the use of slit lamp digital photography, confocal microscopy (CM) and optical coherence tomography (OCT). A review of the literature describing the histopathological and genetic associations of stromal dystrophies, suggest it may be possible to differentiate dystrophies based on their clinical manifestations, and appearances of CM and OCT images, with or without the use of genetic testing.

CASE REPORT

Two sisters, previously diagnosed with Granular (Groenouw I) Dystrophy, were examined. Examination included the use of digital slit lamp photography, CM and OCT imaging.

RESULTS

"Breadcrumb" opacities were visualized in the anterior two-thirds of the stroma with all three imaging techniques. Opacities were demonstrated in the posterior third of the stroma with the digital photography and OCT techniques.

CONCLUSIONS

The digital photography, CM and OCT images support the sister's diagnosis of Granular (Groenouw I) Dystrophy. Currently, genetic and histopathological testing are the only techniques available to determine exactly which corneal dystrophy and gene mutation are present. The results of this case report demonstrate that slit lamp digital photography, combined with CM and OCT may be capable of providing sufficient diagnostic information to diagnose corneal granular dystrophies in a clinical setting.

Corneal dystrophy-associated R124H mutation disrupts TGFBI interaction with Periostin and causes mislocalization to the lysosome

The 5q31-linked corneal dystrophies are heterogeneous autosomal-dominant eye disorders pathologically characterized by the progressive accumulation of aggregated proteinaceous deposits in the cornea, which manifests clinically as severe vision impairment. The 5q31-linked corneal dystrophies are commonly caused by mutations in the TGFBI (transforming growth factor-beta-induced) gene. However, despite the identification of the culprit gene, the cellular roles of TGFBI and the molecular mechanisms underlying the pathogenesis of corneal dystrophy remain poorly understood. Here we report the identification of periostin, a molecule that is highly related to TGFBI, as a specific TGFBI-binding partner. The association of TGFBI and periostin is mediated by the amino-terminal cysteine-rich EMI domains of TGFBI and periostin. Our results indicate that the endogenous TGFBI and periostin colocalize within the trans-Golgi network and associate prior to secretion. The corneal dystrophy-associated R124H mutation in TGFBI severely impairs interaction with periostin in vivo. In addition, the R124H mutation causes aberrant redistribution of the mutant TGFBI into lysosomes. We also find that the periostin-TGFBI interaction is disrupted in corneal fibroblasts cultured from granular corneal dystrophy type II patients and that periostin accumulates in TGFBI-positive corneal deposits in granular corneal dystrophy type II (also known as Avellino corneal dystrophy). Together, our findings suggest that TGFBI and periostin may play cooperative cellular roles and that periostin may be involved in the pathogenesis of 5q31-linked corneal dystrophies.

Clinical and genetic features of TGFBI-linked corneal dystrophies in Mexican population: description of novel mutations and novel genotype-phenotype correlations

Corneal dystrophies (CDS) are inherited disorders characterized by an altered corneal transparency and refractive index which may be caused by a progressive accumulation of deposits within the different corneal layers. Most CDs are inherited in an autosomal dominant fashion and mutations in the TGFBI gene at chromosome 5q31 cause the majority of CDs affecting the stromal layer. A genotype-phenotype correlation has been identified in most analyzed populations as specific amino acid changes in TGFBI protein cause specific stromal phenotypes. However, analysis of additional populations will help to broaden the mutational spectrum ultimately allowing a better clinical-molecular classification of patients with this group of diseases. In this work, eighteen unrelated Mexican probands suffering from stromal CDs were clinically assessed and their TGFBI gene status investigated. Complete ophthalmologic evaluation, including biomicroscopic inspection and dilated fundus examination, was performed. In addition, detailed genealogical analyses as well as automated DNA sequencing of the entire TGFBI gene were done in all probands. Mutation-carrying exons were examined in 50 first and second degree relatives. Phenotypic analysis disclosed the occurrence of 6 cases of lattice CD, 6 of granular CD, 2 of granular type 2 (Avellino CD), 2 of polymorphic corneal amyloidosis, 1 of Reis-Bucklers CD, and 1 of an unclassifiable phenotype. TGFBI mutations were identified in all 18 probands. A total of six different mutations were observed: p.V113I, p.M502V, p.A546D, p.L550P, p.R555W, and p.H626R. Of these, mutations p.L550P (originated by the change c.1649T>C at exon 12), p.M502V (c.1504A>G, at exon 11), and p.V113I (c.337G>A, at exon 4), are novel TGFBI mutations. All subjects with lattice CD in our sample carried the p.H626R mutation. No instances of defects at codon 124, one of the two most frequently mutated sites in TGFBI-linked CDs, were detected. A distinct TGFBI mutational pattern was identified in Mexican patients with stromal CDs. Novel TGFBI mutations and new genotype-phenotype correlations were also recognized. This study stresses the importance of performing TGFBI genetic analysis in distinct CD populations.

Corneal dystrophies

The term corneal dystrophy embraces a heterogenous group of bilateral genetically determined non-inflammatory corneal diseases that are restricted to the cornea. The designation is imprecise but remains in vogue because of its clinical value. Clinically, the corneal dystrophies can be divided into three groups based on the sole or predominant anatomical location of the abnormalities. Some affect primarily the corneal epithelium and its basement membrane or Bowman layer and the superficial corneal stroma (anterior corneal dystrophies), the corneal stroma (stromal corneal dystrophies), or Descemet membrane and the corneal endothelium (posterior corneal dystrophies). Most corneal dystrophies have no systemic manifestations and present with variable shaped corneal opacities in a clear or cloudy cornea and they affect visual acuity to different degrees. Corneal dystrophies may have a simple autosomal dominant, autosomal recessive or X-linked recessive Mendelian mode of inheritance. Different corneal dystrophies are caused by mutations in the CHST6, KRT3, KRT12, PIP5K3, SLC4A11, TACSTD2, TGFBI, and UBIAD1 genes. Knowledge about the responsible genetic mutations responsible for these disorders has led to a better understanding of their basic defect and to molecular tests for their precise diagnosis. Genes for other corneal dystrophies have been mapped to specific chromosomal loci, but have not yet been identified. As clinical manifestations widely vary with the different entities, corneal dystrophies should be suspected when corneal transparency is lost or corneal opacities occur spontaneously, particularly in both corneas, and especially in the presence of a positive family history or in the offspring of consanguineous parents. Main differential diagnoses include various causes of monoclonal gammopathy, lecithin-cholesterol-acyltransferase deficiency, Fabry disease, cystinosis, tyrosine transaminase deficiency, systemic lysosomal storage diseases (mucopolysaccharidoses, lipidoses, mucolipidoses), and several skin diseases (X-linked ichthyosis, keratosis follicularis spinolosa decalvans). The management of the corneal dystrophies varies with the specific disease. Some are treated medically or with methods that excise or ablate the abnormal corneal tissue, such as deep lamellar endothelial keratoplasty (DLEK) and phototherapeutic keratectomy (PTK). Other less debilitating or asymptomatic dystrophies do not warrant treatment. The prognosis varies from minimal effect on the vision to corneal blindness, with marked phenotypic variability.

The IC3D classification of the corneal dystrophies

BACKGROUND

The recent availability of genetic analyses has demonstrated the shortcomings of the current phenotypic method of corneal dystrophy classification. Abnormalities in different genes can cause a single phenotype, whereas different defects in a single gene can cause different phenotypes. Some disorders termed corneal dystrophies do not appear to have a genetic basis.

PURPOSE

The purpose of this study was to develop a new classification system for corneal dystrophies, integrating up-to-date information on phenotypic description, pathologic examination, and genetic analysis.

METHODS

The International Committee for Classification of Corneal Dystrophies (IC3D) was created to devise a current and accurate nomenclature.

RESULTS

This anatomic classification continues to organize dystrophies according to the level chiefly affected. Each dystrophy has a template summarizing genetic, clinical, and pathologic information. A category number from 1 through 4 is assigned, reflecting the level of evidence supporting the existence of a given dystrophy. The most defined dystrophies belong to category 1 (a well-defined corneal dystrophy in which a gene has been mapped and identified and specific mutations are known) and the least defined belong to category 4 (a suspected dystrophy where the clinical and genetic evidence is not yet convincing). The nomenclature may be updated over time as new information regarding the dystrophies becomes available.

CONCLUSIONS

The IC3D Classification of Corneal Dystrophies is a new classification system that incorporates many aspects of the traditional definitions of corneal dystrophies with new genetic, clinical, and pathologic information. Standardized templates provide key information that includes a level of evidence for there being a corneal dystrophy. The system is user-friendly and upgradeable and can be retrieved on the website www.corneasociety.org/ic3d.

A novel variant of combined granular-lattice corneal dystrophy associated with the Met619Lys mutation in the TGFBI gene

OBJECTIVE

To report a novel mutation in TGFBI (GenBank NM_000358), p.Met619Lys, associated with a variant of combined granular-lattice corneal dystrophy.

METHODS

Slitlamp examination and DNA collection from the proband and affected and unaffected relatives. All 17 exons of TGFBI were amplified and sequenced in the proband. Exon 14 was amplified and sequenced in the proband's family members and in 100 controls. Histopathologic examination of the excised corneal buttons from the proband and 3 family members was also performed.

RESULTS

Affected individuals demonstrated an age-dependent phenotype, with the progression from central subepithelial needlelike deposits in younger individuals to polymorphic anterior stromal opacities in older family members. Screening of TGFBI in the proband demonstrated a novel mutation, p.Met619Lys, which was also present in all affected family members. Histopathologic examination revealed stromal deposits that stained with the Congo red and Masson trichrome stains as well as an antibody to the protein product of TGFBI.

CONCLUSIONS

We present a unique corneal dystrophy phenotype associated with the novel p.Met619Lys mutation in TGFBI. Clinical Relevance The atypical and variable phenotype and the demonstration of both hyaline and amyloid stromal deposits indicate that neither clinical nor histopathologic features may be relied on to accurately diagnose and classify the corneal dystrophies.

Spontaneous and inheritable R555Q mutation in the TGFBI/BIGH3 gene in two unrelated families exhibiting Bowman's layer corneal dystrophy

PURPOSE

Bowman's layer corneal dystrophies (CDBs) include 2 distinct types: CDB1, or Reis-Bücklers (RBCD), and CDB2, or Thiel-Behnke (TBCD). We studied the genetic basis of 2 cases of apparent spontaneous CDB mutations and attempted to determine if these are sporadic and inheritable mutations.

DESIGN

Retrospective molecular genetic study and case report.

PARTICIPANTS

Twelve patients were recruited from 2 unrelated families for this study, including 2 affected individuals from one family (family A) and 1 affected individual from another (family B).

METHODS

Slit-lamp examination was performed for each patient to determine the disease phenotype. Histological analysis of affected cornea specimens was used for identification of pathogenic corneal opacities in 2 affected patients from family A.

MAIN OUTCOME MEASURES

Genomic DNA was isolated from the blood samples and used for mutation screening of the TGFBI/BIGH3 gene. Sixteen polymorphic DNA markers from 9 different chromosomes were used to establish the maternity and paternity of the 2 probands.

RESULTS

The 2 families were confirmed to be unrelated. The age onset of ocular symptoms was <2 years for all 3 affected patients. Clinical diagnoses of CDB1 (RBCD) and CDB2 (TBCD) were made for probands A and B, respectively. The affected corneas showed epithelial haze with diffuse, irregular, patchy opacities in a honeycomb and geographic pattern. Subepithelial plaques, increased trichome staining of anterior stroma, and irregular Bowman's layer were observed. An R555Q mutation was found in TGFBI/BIGH3 in the 2 probands but not in their parents. The son of proband A was also affected and apparently inherited his disease allele from his father.

CONCLUSION

The R555Q mutation occurred spontaneously and independently in the 2 unrelated CDB families and was confirmed to be transmitted to the next generation in 1 of the 2 families. These findings strongly support the notion that a genetic diagnosis should be determined for CDB and other dystrophies associated with mutations in TGFBI/BIGH3. The discovery of a spontaneous mutation should alert clinicians to be aware of the existence of genetic alterations for their patients without apparent family history of the disease.

TGFBI gene mutations in corneal dystrophies

The lattice corneal dystrophies (LCD) and granular corneal dystrophies (GCD) are autosomal dominant disorders of the corneal stroma. They are bilateral, progressive conditions characterized by the formation of opacities arising due to the deposition of insoluble material in the corneal stroma leading to visual impairment. The LCDs and GCDs are distinguished from each other and are divided into subtypes on the basis of the clinical appearance of the opacities, clinical features of the disease, and on histopathological staining properties of the deposits. The GCDs and most types of LCD arise from mutations in the transforming growth factor beta-induced (TGFBI) gene on chromosome 5q31. Over 30 mutations causing LCD and GCD have been identified so far in the TGFBI. There are two mutation hotspots corresponding to arginine residues at positions 124 and 555 of the transforming growth factor beta induced protein (TGFBIp) and they are the most frequent sites of mutation in various populations. Mutations at either of these two hotspots result in specific types of LCD or GCD. The majority of identified mutations involve residues in the fourth fasciclin-like domain of TGFBIp.

Epithelial cell, keratocyte, and endothelial cell apoptosis in Fuchs' dystrophy and in pseudophakic bullous keratopathy

PURPOSE

To elucidate the pathomechanism of Fuchs' dystrophy and pseudophakic bullous keratopathy (PBK) by examining cell apoptosis in different corneal layers.

METHODS

The authors studied corneal buttons obtained from 21 eyes following central penetrating keratoplasty: 14 corneal buttons (13 patients, age 70.8+/-10.0 years) with Fuchs' dystrophy, and 7 buttons (7 patients, age 69.6+/-10.2 years) with PBK. Four buttons from enucleated eyes with choroidal melanoma served as controls. Histologic changes were examined using light microscopy with hematoxylin-eosin (HE) staining. The average numbers of apoptotic cells per field of view (125x magnification) in separate samples of the epithelial, stromal, and endothelial layers were determined using the TUNEL (terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling) assay.

RESULTS

In 11 of the Fuchs' dystrophy corneas and 2 of the PBK corneas, apoptotic activity was detected. In the control corneas no apoptotic activity was found. Compared to the controls there was a statistically significant difference in the mean (normalized) apoptotic cell numbers for all three layers (p=0.01 in each case) in the Fuchs' dystrophy corneas, and for the stromal layer (p<0.01) in PBK corneas. The apoptotic cell numbers for the epithelial and endothelial layers of the latter were higher, but the difference was not statistically significant (p=0.07, 0.07).

CONCLUSIONS

Apoptosis may play a role in the pathomechanism of Fuchs' dystrophy and in keratocyte death in corneas with PBK.

Rapid genotyping for most common TGFBI mutations with real-time polymerase chain reaction

Recent studies of the corneal dystrophies (CDs) have shown that most cases of granular CD, Avellino CD, and lattice CD type I are caused by mutations in the human transforming growth factor beta-induced (TGFBI) gene. The aim of this study was to develop a rapid diagnostic assay to detect mutations in the TGFBI gene. Sixty-six patients from 64 families with TGFBI-associated CD were studied. A primer probe set was designed to examine the genome from exons 4 and 12 of the TGFBI gene in order to identify mutant and wild-type alleles. A region spanning the mutations was amplified by the polymerase chain reaction (PCR) in a commercial cycler. Mutations were then identified by melting curve analysis of the hybrid formed between the PCR product and a specific fluorescent probe. Using this system, we clearly distinguished each CD genotype (homozygous and heterozygous 418G-->A, heterozygous 417C-->T, heterozygous 1710C-->T, and wild-type) of all the patients by means of the clearly distinct melting peaks at different temperatures. One thermal cycling took approximately 54 min, and all results were completely in concordance with the genotypes determined by conventional DNA sequencing. Thus, the technique is accurate and can be used for routine clinical diagnosis. We expect that our new method will help in making precise diagnoses of patients with atypical CDs and aid the revision of the clinical classification of inherited corneal diseases based on the genetic pathogenesis.

TGFBI Gene Mutation Analysis in Families with Hereditary Corneal Dystrophies from Ukraine

In our study, 5 previously reported mutations of the TGFBI gene - R124C, R124H, R124L (exon 4), R555W, R555Q (exon 12) - were analyzed using polymerase chain reaction followed by restriction digestion in 48 individuals from 19 unrelated families with different forms of corneal dystrophy from different regions of Ukraine. The R555W mutation was detected in 6 patients from 4 families with granular corneal dystrophy. The R124C mutation was detected in 1 unaffected 10-year-old individual and in 24 patients from 8 families with lattice corneal dystrophy. As far as the R124C mutation detected in 1 patient with clinically diagnosed Reis-Bucklers corneal dystrophy is concerned, we concluded that this patient was misdiagnosed. The obtained results show that TGFBI gene mutation analysis is important as well for the early differential diagnosis of corneal dystrophies and genetic consulting in high-risk families.

Impact of phototherapeutic keratectomy on the outcome of subsequent penetrating keratoplasty in patients with stromal corneal dystrophies

PURPOSE

To examine the impact of previous phototherapeutic keratectomy (PTK) on the outcome of subsequent penetrating keratoplasty (PK) in patients with stromal corneal dystrophies.

DESIGN

Retrospective, cross-sectional, clinical single-center study.

METHODS

PATIENT POPULATION

Fifteen patients (21 eyes) age 39.9 +/- 11.4 years.

INCLUSION CRITERIA

Primary homologous PK performed in phakic patients with granular or macular dystrophy; no use of combined surgical procedures; defined graft size and technique. The study group comprised eight eyes of five patients, PK performed 3.7 +/- 2.3 years after PTK. The control group (no previous PTK) comprised 13 eyes of 10 patients. In both groups, 38% had granular and 62% had macular dystrophy. Intervention Procedures: Phototherapeutic keratectomy was performed using a 193 nm excimer laser. All PKs were also performed using this laser, with trephination using a metal mask. Subjective refractometry (trial lenses), standard keratometry (Zeiss ophthalmometer), and corneal topography (Tomey TMS-1) were performed preoperatively, 6 months after PK, and after first and second suture removal (1.1 +/- 0.2 years; 1.6 +/- 0.2 years).

MAIN OUTCOME MEASURES

Keratometric, topographic net astigmatism, and refractive cylinder; keratometric and topographic central power; best-corrected visual acuity (BCVA); surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA).

RESULTS

Refractive power and astigmatism, BCVA, and PVA values did not differ significantly between the two groups at any time-point; SRI tended to be better in the study group after first suture removal (P =.05).

CONCLUSION

Preceding PTK does not appear to impair the outcome of subsequent penetrating keratoplasty in stromal corneal dystrophy patients.

Phototherapeutic keratectomy for BIGH3-linked corneal dystrophy recurring after penetrating keratoplasty

PURPOSE

To determine visual results and report side effects and complications after phototherapeutic keratectomy (PTK) for BIGH3-linked corneal dystrophy recurring after penetrating keratoplasty.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Forty-two excimer laser PTK procedures were performed in 42 eyes of 29 patients with BIGH3-linked corneal dystrophies. Genetic status of all patients was determined and allowed us to assess an unambiguous diagnosis. Preoperative diagnoses included LCDIIIA/A546T (1 eye), R124 l+DT125-DE126 (4 eyes), GICD/R555W (14 eyes), LCDI/R124C (6 eyes), SGD/R124 l (16 eyes), and CDBII/R555Q (1 eye).

INTERVENTION

Two excimer lasers (Summit Excimed UV 200, Summit Technology, Waltham, MA and Nidek EC 5000, Nidek, Inc., Gamagori, Japan) were used to perform all PTKs. Indications for performing PTK after a graft were severe decrease of the best-corrected visual acuity (BCVA) related to recurrent corneal deposits and/or painful recurrent epithelial erosions.

MAIN OUTCOME MEASURES

Preoperative and postoperative BCVA were analyzed, significant recurrences after treatment were noted, and postoperative complications were recorded.

RESULTS

Mean preoperative BCVA was 0.2 +/- 0.12 in the decimal chart, mean postoperative BCVA was 0.52 +/- 0.16 with a mean follow-up of 3.13 +/- 1.77 years (range, 0.3-6.65 years). Visual acuity was significantly improved after surgery (P < 0.05). The magnitude of the change in visual acuity was dependent on the mutation (P < 0.001). Seven symptomatic recurrences were observed. One regressive graft rejection and 4 cases of severe postoperative haze were observed. No other complications were noted.

CONCLUSIONS

PTK is a simple, safe, and efficient technique for the treatment of recurrent corneal dystrophies; in many cases it prevents or delays the major incumbent problems of repeated grafting.

Clinical, histopathologic, and ultrastructural characteristics of BIGH3(TGFBI) amyloid corneal dystrophies are supportive of the existence of a new type of LCD: the LCDi

PURPOSE

To assess the morphologic differences of three types of lattice corneal dystrophies (LCDs) from histologic, immunohistochemical, and ultrastructural studies.

METHODS

Corneas from three patients, one LCD1, one His626Arg-LCD, and one LCD3A were processed for Congo red, betaig-h3(541-564) antibodies immunostaining, and electron transmission microscopy studies. Control tissues were submitted to identical analyses and consisted of one cornea from a patient not having LCD and one skin biopsy from the patient suffering from LCD1.

RESULTS

The three corneas displayed birefringent congophilic deposits under polarized light, confirming their amyloid nature. The deposits differed regarding their shape and location in each of the corneas. A strong immunoreactivity for betaig-h3 was shown in the LCD1 and His626Arg-LCD deposits, which was faint for the LCD3A deposits. Ultrastructural analysis confirmed the dissimilarity of the deposits among the different types of LCD. No amyloid deposits were observed in the skin from the LCD1 patient, whereas immunostaining showed the presence of high amounts of betaig-h3.

CONCLUSION

Our results show that betaig-h3 is involved in amyloid deposition in all the LCDs included in the study (LCD1, His626Arg-LCD, and LCD3A). These three forms of LCD, clinically different, were also distinguishable histologically, confirming that they belong to distinctive groups of LCDs. The absence of amyloid deposition in skin from the LCD1 patient supports cornea-specific amyloid formation. In light of the present clinical, histologic, and ultrastructural data, His626Arg and related LCDs constitute a separate group of LCD that could be considered as of intermediate type on clinical grounds.

Clinical outcome of eight BIGH3-linked corneal dystrophies

OBJECTIVE

To determine whether the mutational pattern of BIGH3-linked corneal dystrophies (CDs) can accurately predict the clinical course of the disease and be helpful in planning adequate surgical treatment.

DESIGN

Retrospective noncomparative case series.

PARTICIPANTS

Chart review of 73 patients (110 eyes) with recently confirmed BIGH3 mutations who underwent a penetrating keratoplasty (PK) from 1978 through 1999. Diagnoses included Thiel-Benhke CD (TBCD/R555Q) (13 eyes), classic granular CD (CGCD/R555W) (28 eyes), superficial variant of granular dystrophy (SVGD/R124 l) (27 eyes), lattice CD type I (LCDI/R124C) (20 eyes), Avellino CD (ACD/R124H) (2 eyes), H626R-lattice dystrophy (LCD/H626R) (6 eyes), and two novel dystrophies: a French variant of granular dystrophy (FVGD/R124 l+DT125-DE126) (9 eyes) and a French lattice CD type IIIA (LCDIIIA/A546T) (5 eyes).

METHODS

The mutation of the BIGH3 gene was characterized for all patients. Clinical data were reviewed for each patient, and included age at first PK and elapsed time before significant recurrence (as defined by a severe decrease in best-corrected visual acuity related to recurrent deposits in the graft).

MAIN OUTCOME MEASURES

Mean age at first PK and delay before a significant recurrence.

RESULTS

Mutational pattern was highly correlated with the clinical course of each dystrophy. According to the genetic mutation, two groups with different prognosis were identified. Group 1 was defined by the presence of the FVGD/R124 l+DT125-DE126 and SVGD/R124 l mutations and was characterized by the early need for treatment and early recurrence of deposits. Group 2 was molecularly defined by the presence of any of the following mutations: LCDI/R124C, CGCD/R555W, LCDIIIA/A546T, TBCD/R555Q, and LCD/H626R. In group 2, mean age at first treatment was older, and delay before a significant recurrence was longer as compared with group 1 (P = 0.0001).

CONCLUSIONS

These results demonstrate that there is a direct correlation between the molecular defect and the clinical course of BIGH3-linked CDs. They also indicate that molecular characterization of the genetic defect will help predict and design adequate surgical treatment for patients with ambiguous clinical diagnosis.