Gelatino-lattice corneal dystrophy: clinical features and mutational analysis

A Case of Clinically Atypical Gelatinous Drop-like Corneal Dystrophy With Unilateral Recurrent Amyloid Depositions

PURPOSE

The purpose of this article was to describe the successful diagnosis and management of clinically atypical, unilateral, gelatinous drop-like corneal dystrophy (GDLD) in a pediatric patient.

METHODS

This study was a case report.

RESULTS

A 7-year-old Japanese girl was referred to our clinic with right corneal opacity for over 3 years. Slitlamp examination revealed a white, protruding, paracentral corneal opacity with an irregular surface and tiny stromal lattice figures with subepithelial opacities. No trichiasis or epiblepharon was observed, and the patient's right corrected distance visual acuity (CDVA) was 18/20. The contralateral cornea was intact but demonstrated fluorescein uptake. After 8 months, the right CDVA worsened from 18/20 to 6/20, and corneal epithelial scraping was performed. Histopathological analysis revealed amyloid nodules in the subepithelial layer and in the anterior corneal stroma stained with Congo red, which reoccurred 2 months after the procedure, and corneal dystrophy was suspected. Isolation and sequencing of the genomic DNA revealed a homozygous p.Gln118Ter. mutation in TACSTD2 in the patient and heterozygous p.Gln118Ter. mutations in both parents. GDLD was diagnosed; bilateral use of therapeutic soft contact lenses was prescribed after the first corneal scraping. No additional surgical intervention was required for the right eye for 4.5 years. CDVA of the contralateral left eye has been successfully maintained at 30/20 over this period, without emergence of nodular lesions or corneal opacities.

CONCLUSIONS

We encountered a patient with early, atypical GDLD, who was definitively diagnosed using genomic DNA sequencing. GDLD should be a part of the differential diagnosis in patients presenting with unilateral, recurrent amyloid deposition.

Gelatinous drop-like corneal dystrophy: a review

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive form of corneal dystrophy characterised by subepithelial and stromal amyloid deposits. It is relatively common in Japan. It usually presents in the first two decades of life with subepithelial nodular lesions that later coalesce to form mulberry-like opacities. Although various surgical modalities have been attempted, recurrence remains a major challenge.

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.

Gelatinous drop-like corneal dystrophy in a child with developmental delay: clinicopathological features and exclusion of the M1S1 gene

AIMS

Gelatinous drop-like corneal dystrophy (GDLD) is an early-onset, autosomal recessive condition characterised by amyloid deposits within the cornea. We report the histopathological and molecular genetic findings in a Caucasian child with GDLD who also exhibited global developmental delay.

METHODS

Bilateral lamellar keratoplasty was carried out at age 6 and 7 years. Tissue was fixed for light and electron microscopy, including immunoelectronmicroscopy. The coding region of the M1S1 gene was screened for mutations in the affected proband and available relatives, using DNA extracted from mouthwashes.

RESULTS

Nodular deposits, which were present subepithelially and in the central superficial stroma, stained typically for amyloid with PAS and Congo red. A nodular deposit of amyloid, together with large amounts of lactoferrin and sparse amounts of keratoepithelin (betaig-h3), was present in the central superficial stroma, causing destruction of Bowman's layer and elevation of the thinned, degenerate epithelium. Around the deposit zone, the stroma exhibited large numbers of thick filamentous proteoglycan deposits. While the affected child was homozygous for a novel A1133 C single-nucleotide polymorphism (SNP) that resulted in an aspartic acid to alanine substitution at position 173 of the M1S1 coding sequence, this polymorphism was also found at relatively high frequency in a sample of normal controls, enabling exclusion of the M1S1 gene as the disease locus.

CONCLUSION

Increased epithelial permeability in GDLD may be explained in part by an altered membrane permeability of the superficial epithelial cells. An association with developmental delay has not been reported previously.

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.

Lattice corneal dystrophy associated with the Ala546Asp and Pro551Gln missense changes in the TGFBI gene

PURPOSE

To report a phenotypic variant of lattice corneal dystrophy associated with two missense changes, Ala546Asp and Pro551Gln, in the transforming growth factor-beta-induced gene (TGFBI).

DESIGN

Experimental study.

METHODS

Genomic DNA was obtained from the proband as well as affected and unaffected family members. Exons 4, 11, 12, and 14 of the TGFBI gene were amplified and sequenced. Additionally, a corneal button excised from the proband was examined by light and transmission electron microscopy. Haplotype analysis was performed on the proband's family and members of a previously identified pedigree with the same TGFBI gene missense changes.

RESULTS

Bilateral, symmetric, radially arranged, branching refractile lines within and surrounding an area of central anterior stromal haze were noted in the proband. Multiple polymorphic, refractile deposits were noted in the mid and posterior stroma in both the proband and her daughter. Light and electron microscopic analyses demonstrated amyloid and excluded the presence of deposits characteristic of granular corneal dystrophy. Screening of TGFBI exon 12 in the proband and her affected daughter revealed two missense changes, Ala546Asp and Pro551Gln (both absent in 250 control chromosomes). Haplotype analysis suggested that the mutations in this family and in a previously identified pedigree reflect a founder effect, rather than an independent occurrence.

CONCLUSIONS

We present a phenotypic variant of lattice corneal dystrophy associated with the Ala546Asp and Pro551Gln missense changes in exon 12 of the TGFBI gene. A common ancestor appears to account for the missense mutations observed in this pedigree and in a previously reported family.

Two brothers with gelatinous drop-like dystrophy at different stages of the disease: role of mutational analysis

PURPOSE

A report of two Japanese brothers with gelatinous drop-like corneal dystrophy, one with and one without the typical gelatinous drop-like region.

DESIGN

Interventional case report and observational case report.

METHODS

After penetrating keratoplasty, the corneal button, right eye, of the elder brother, 39 years of age, was stained and examined by microscopy. The M1S1 and BIGH3 genes were examined for mutations using the polymerase chain reaction and direct sequencing. Corneal abnormalities in the younger brother, 37 years of age, were observed.

RESULTS

The elder brother had bilateral gelatinous prominences and band-shaped corneal opacities, whereas the younger brother had only bilateral band-shaped opacities. Histologically, corneal deposits beneath the epithelium stained with Congo red. Molecular genetic analysis revealed that M1S1 was homozygously mutated in both brothers (Q118X).

CONCLUSION

The Q118X mutation of the M1S1 gene can produce either a gelatinous drop-like region or band-shaped opacities.