IC3D Classification of Corneal Dystrophies-Edition 3

PURPOSE

The International Committee for the Classification of Corneal Dystrophies (IC3D) was created in 2005 to develop a new classification system integrating current information on phenotype, histopathology, and genetic analysis. This update is the third edition of the IC3D nomenclature.

METHODS

Peer-reviewed publications from 2014 to 2023 were evaluated. The new information was used to update the anatomic classification and each of the 22 standardized templates including the level of evidence for being a corneal dystrophy [from category 1 (most evidence) to category 4 (least evidence)].

RESULTS

Epithelial recurrent erosion dystrophies now include epithelial recurrent erosion dystrophy, category 1 ( COL17A1 mutations, chromosome 10). Signs and symptoms are similar to Franceschetti corneal dystrophy, dystrophia Smolandiensis, and dystrophia Helsinglandica, category 4. Lisch epithelial corneal dystrophy, previously reported as X-linked, has been discovered to be autosomal dominant ( MCOLN1 mutations, chromosome 19). Classic lattice corneal dystrophy (LCD) results from TGFBI R124C mutation. The LCD variant group has over 80 dystrophies with non-R124C TGFBI mutations, amyloid deposition, and often similar phenotypes to classic LCD. We propose a new nomenclature for specific LCD pathogenic variants by appending the mutation using 1-letter amino acid abbreviations to LCD. Pre-Descemet corneal dystrophies include category 1, autosomal dominant, punctiform and polychromatic pre-Descemet corneal dystrophy (PPPCD) ( PRDX3 mutations, chromosome 10). Typically asymptomatic, it can be distinguished phenotypically from pre-Descemet corneal dystrophy, category 4. We include a corneal dystrophy management table.

CONCLUSIONS

The IC3D third edition provides a current summary of corneal dystrophy information. The article is available online at https://corneasociety.org/publications/ic3d .

Lisch Epithelial Corneal Dystrophy Is Caused by Heterozygous Loss-of-Function Variants in MCOLN1

PURPOSE

To report the genetic etiology of Lisch epithelial corneal dystrophy (LECD).

DESIGN

Multicenter cohort study.

METHODS

A discovery cohort of 27 individuals with LECD from 17 families, including 7 affected members from the original LECD family, 6 patients from 2 new families and 14 simplex cases, was recruited. A cohort of 6 individuals carrying a pathogenic MCOLN1 (mucolipin 1) variant was reviewed for signs of LECD. Next-generation sequencing or targeted Sanger sequencing were used in all patients to identify pathogenic or likely pathogenic variants and penetrance of variants.

RESULTS

Nine rare heterozygous MCOLN1 variants were identified in 23 of 27 affected individuals from 13 families. The truncating nature of 7 variants and functional testing of 1 missense variant indicated that they result in MCOLN1 haploinsufficiency. Importantly, in the homozygous and compound-heterozygous state, 4 of 9 LECD-associated variants cause the rare lysosomal storage disorder mucolipidosis IV (MLIV). Autosomal recessive MLIV is a systemic disease and comprises neurodegeneration as well as corneal opacity of infantile-onset with epithelial autofluorescent lysosomal inclusions. However, the 6 parents of 3 patients with MLIV confirmed to carry pathogenic MCOLN1 variants did not have the LECD phenotype, suggesting MCOLN1 haploinsufficiency may be associated with reduced penetrance and variable expressivity.

CONCLUSIONS

MCOLN1 haploinsufficiency is the major cause of LECD. Based on the overlapping clinical features of corneal epithelial cells with autofluorescent inclusions reported in both LECD and MLIV, it is concluded that some carriers of MCOLN1 haploinsufficiency-causing variants present with LECD.

The eye is a common site of granulomatosis with polyangiitis. A collaborative study

BACKGROUND

Ocular manifestations of granulomatosis with polyangiitis (GPA) have been reported in a limited number of studies and with largely variable frequency. Here we report on the clinical, diagnostic, and therapeutic features of a cohort of 63 GPA patients, with particular regard to 22 of them with ophthalmic involvement (35%).

METHODS

Clinical manifestations, results of immunological findings, histopathological pictures, imaging data, Birmingham Vasculitis Activity Score, therapeutic regimens, and outcomes were retrospectively analyzed. At diagnosis, in addition to a structured clinical assessment, all patients underwent a comprehensive ophthalmologic examination.

RESULTS

The most frequently involved organs were kidneys, lungs, ear/nose/throat, and eyes. Ocular manifestations were bilateral in 32%. The three most commonly diagnosed ophthalmologic manifestations were scleritis (36%), retro-orbital pseudotumor or orbital mass (23%), and episcleritis (13%). Ocular and systemic involvement were simultaneously present at onset in 41% of the patients; systemic involvement was followed by ocular lesions in 36%; ocular inflammation was followed by systemic manifestations in 18%; and an orbital mass in the absence of systemic disease characterized 5%. Glucocorticoids plus cyclophosphamide and glucocorticoids plus rituximab were the combined therapies most frequently employed during remission induction and remission maintenance, respectively. Persistent ophthalmologic and extra-ocular remissions were achieved in 77 and 64% of the patients, respectively. One to three systemic relapses were diagnosed in 7 patients (31.8%). At the last follow-up, a visual outcome 20/40 or better in 31 (70%) of 44 eyes was determined.

CONCLUSIONS

The eye was involved in over one third of our patients with GPA. Increased awareness, early diagnosis, and multi-specialty collaboration are critical in achieving a favorable outcome of GPA.

Update on the Corneal Dystrophies-Genetic Testing and Therapy

ABSTRACT

One major purpose of the IC3D Corneal Dystrophy Nomenclature Revision was to include genetic information with a goal of facilitating investigation into the pathogenesis, treatment, and perhaps even prevention of the corneal dystrophies, an ambitious goal. Over a decade has passed since the first publication of the IC3D Corneal Dystrophy Nomenclature Revision. Gene therapy is available for an early-onset form of inherited retinal degeneration called Leber congenital amaurosis, but not yet for corneal degenerations. We review the current state of affairs regarding our original ambitious goal. We discuss genetic testing, gene therapy [RNA interference (RNAi) and genome editing], and ocular delivery of corneal gene therapy for the corneal dystrophies. Why have gene therapy techniques not yet been introduced for the corneal dystrophies?

The Spectrum of Ocular Manifestations in Patients with Waldenström's Macroglobulinemia

PURPOSE

To investigate the ocular manifestations in 91 Waldenström's macroglobulinemia (WM) patients.

METHODS

Retrospective, cross-sectional, observational analysis.

RESULTS

Ocular impairments, detected in 19 patients, included flame-shaped hemorrhages, venous sausaging, papilledema, macular detachments, or central retinal vein occlusion in 16 patients; paraproteinemic keratopathy in 2; and a CANOMAD syndrome in 1. Best-corrected visual acuity was ≥0.5 logMAR units in 11 of 38 eyes. Intraocular pressure was increased in seven eyes. Genetic analysis in seven patients showed a mutation in the MYD88 gene in six patients and a nonsense mutation in the CXCR4 gene in five patients. Plasmapheresis followed by chemotherapy with or without the addition of rituximab resulted in improvement or normalization of the ophthalmological findings in 15 patients.

CONCLUSION

The ocular manifestations of WM are protean and potentially sight threatening. Recent advances in genomic profiling and chemotherapy have remarkably improved the hematological and ophthalmological outcomes of these patients.

Monoclonal gammopathy of ocular significance (MGOS) - a short survey of corneal manifestations and treatment outcomes

Monoclonal gammopathy of ocular significance (MGOS) is a rare subset of monoclonal gammopathy of clinical significance occurring secondary to plasma cell disorders and causing ocular manifestations. We identified 23 patients with paraproteinemic keratopathy (PPK) in the setting of monoclonal gammopathy of unknown significance (MGUS, 10), smoldering multiple myeloma (SMM, 3) or multiple myeloma (MM, 10). Many of these patients with PPK (11/23) presented decreased vision. All patients with MM and 40% of those with other diagnoses such as SMM and MGUS received systemic therapy with or without autologous stem cell transplantation. Four eyes of four patients were treated by penetrating keratoplasty. In most cases, neither ocular nor hematologic treatment afforded a durable improvement in the visual acuity (recurrence after a median of 11 months), despite initial responses. Further studies will be required to determine the optimal strategy to treat and prevent the relapse of ocular symptoms in patients with PPK.

Corneal opacity and copper levels of the Lewis syndrome after systemic chemotherapy

Purpose

To report a female patient of biclonal Lewis syndrome which consists of a trias: biclonal gammopathy of undetermined significance, paraproteinemic keratopathy in form of a brownish discoid opacification at the level of Descemet's membrane and hypercupremia. After several years there was a conversion to multiple myeloma. Systemic chemotherapy led to a complete remission of multiple myeloma and to a normalization of the copper level in the blood that lasted five years. The corneal opacification remained unchanged.

Observations

A currently 66-year-old woman suffered from biclonal Lewis syndrome. On both eyes there is a central discoid yellow-brownish discoloration in the Pre-Descemet’s layer. The corneal findings were unchanged after a follow up of eight years. However, there was a conversion to multiple myeloma (MM) type IgG with progressive anemia and suspicious bone lesions. A multiple systemic myeloma-therapy was indicated. Chemotherapy with subsequent tandem autologous-stem cell therapy (auto-SCT) was performed. The blood examination after this therapy showed a complete remission of multiple myeloma, and it was also very surprising that the serum copper level was within normal range. This finding remained unchanged over a period of five years. The bilateral corneal opacification was identical to that before chemotherapy. To the best of our knowledge, this represents the first observation of a normalization of copper levels in Lewis syndrome after chemotherapy.

Conclusions and importance

The Lewis syndrome represents a very rare disorder. The first case reported in Europe (Lisch et al., 2016)¹ showed a conversion from biclonal gammopathy of undetermined significance to MM after a follow-up of 17 years. Subjectively, the patient was in excellent health. The typical corneal, discoid brownish opacification at the level of Descemet's membrane is a suspicious hint of a copper disturbance for the ophthalmologist. The copper level of our patient was extremely elevated. The corneal opacification however, remained unchanged throughout the repeated ophthalmological examinations. In 2015, the conversion of our case with Lewis syndrome to MM performing chemotherapy in different steps and a twice auto-SCT resulted in a complete remission of MM and a normal range of the serum copper. The bilateral corneal opacification remained unchanged during an observation period of five years after chemotherapy.

Early and late clinical landmarks of corneal dystrophies

Corneal dystrophies (CDs) represent a heterogenous group of genetic diseases (Lisch and Weiss, 2019). The International Committee of Classification of Corneal Dystrophies (IC3D) distinguishes between 22 distinct forms of corneal dystrophy (CD) which are predominantly autosomal dominant, although autosomal recessive and X-chromosomal dominant and recessive patterns do exist. A detailed corneal examination of as many affected family members as possible can show the phenotypic differences of the various generations. There are few publications which describe the different CDs with regard to the early and late phenotypes. According to early and late phenotype, three types of CD are generally classified: (1) Thirteen CDs with early and late clinical landmarks. However, it must be pointed out that the different penetrances of the gene often leads to quantitative differences in the corneal phenotype in peers in distinct generations of the same family. (2) Seven CDs with late onset and very little progression of the corneal changes. (3) Two CDs with congenital haze which can be interpreted as the final phenotype of this dystrophy. This applies to autosomal dominant and recessive inheritance.

Amyloidosis and Ocular Involvement: an Overview

Purpose: To describe the ophthalmic manifestations of amyloidosis and the corresponding therapeutic measures.Methods: The 178 patients included in the study had different types of amyloidosis, diagnosed at a single internal medicine institution (Bari, Italy). To provide a comprehensive review of the types of amyloidosis that can be associated with ocular involvement, the images and clinical descriptions of patients with amyloidosis structurally related to gelsolin, keratoepithelin and lactoferrin were obtained in collaborations with the ophthalmology departments of hospitals in Mainz (Germany) and Helsinki (Finland).Results: Overall, ocular morbidity was detected in 41 of the 178 patients with amyloidosis (23%). AL amyloidosis was diagnosed in 18 patients with systemic disease, 3 with multiple myeloma, and 11 with localized amyloidosis. AA amyloidosis was detected in 2 patients with rheumatoid arthritis and 3 with Behçet syndrome, and transthyretin amyloidosis in 4 patients. The treatment of AL amyloidosis is based on chemotherapy to suppress the production of amyloidogenic L-chains and on surgical excision of orbital or conjunctival masses. AA amyloidosis is managed by targeting the underlying condition. Vitreous opacities and additional findings of ocular involvement in patients with transthyretin amyloidosis indicate the need for pars plana vitrectomy. Gelsolin amyloidosis, characterized by lattice corneal amyloidosis and polyneuropathy, results in recurrent keratitis and corneal scarring, such that keratoplasty is inevitable. In patients with lattice corneal dystrophies associated with amyloid deposits of keratoepithelin fragments, corneal transparency is compromised by deposits of congophilic material in the subepithelial layer and deep corneal stroma. Patients with established corneal opacities are treated by corneal transplantation, but the prognosis is poor because recurrent corneal deposits are possible after surgery. In patients with gelatinous drop-like dystrophy, the amyloid fibrils that accumulate beneath the corneal epithelium consist of lactoferrin and can severely impair visual acuity. Keratoplasty and its variants are performed for visual rehabilitation.Conclusion: A routine ophthalmic follow-up is recommended for all patients with established or suspected amyloidosis, independent of the biochemical type of the amyloid. Close collaboration between the ophthalmologist and the internist will facilitate a more precise diagnosis of ocular involvement in amyloidosis and allow the multidisciplinary management of these patients.Abbreviations: CD: corneal dystrophy; CLA: corneal lattice amyloidosis; CNS: central nervous system; CT: computed tomography; FAP: familial amyloidotic polyneuropathy; GDLCD: gelatinous drop-like corneal dystrophy; GLN: gelsolin; LCD: lattice corneal dystrophy; MRI: magnetic resonance imaging; OLT: orthotopic liver transplantation; TEM: transmission electron microscopy; TGFBI: transforming growth factor β induced; TTR: transthyretin.

Epitheliale Dystrophien der Hornhaut

Dieser Beitrag stellt die epithelialen und subepithelialen Hornhautdystrophien gemäß IC3D-Klassifikation und deren Abgrenzung gegenüber den Degenerationen dar. Neben der Einteilung wird auf die Diagnostik und Therapie der Hornhautdystrophien eingegangen; anschließend werden die einzelnen Krankheitsbilder besprochen.

[Epithelial Dystrophies of the Cornea]

In 2015, the first revision of the international classification of corneal dystrophies (IC3D) has been published. According to this latest version of the IC3D the dystrophies of the cornea are divided into · epithelial and subepithelial dystrophies,. · epithelial-stromal TGFBI dystrophies,. · stromal dystrophies, and. · Descemet-membrane and endothelial dystrophies.. This article summarizes the epithelial and subepithelial dystrophies of the cornea, which, according to IC3D are the following: · epithelial basement membrane dystrophy (EBMD),. · epithelial recurrent erosion dystrophy (ERED),. · subepithelial mucinous corneal dystrophy (SMCD),. · Meesmann corneal dystrophy (MECD),. · Lisch epithelial corneal dystrophy (LECD),. · gelatinous drop-like corneal dystrophy (GDLD).. The main problem concerning almost all dystrophies of the corneal epithelium are epithelial defects (erosion) associated with pain, epiphora and red eyes. In addition, all dystrophies of the epithelium tend to relapse.While therapy is usually initiated with topical therapeutics, in the course of the disease invasive procedures like phototherapeutic keratectomy (PTK) (possibly with the administration of mitomycin C) or in severe cases even keratoplasty (preferably as deep anterior lamellar keratoplasty; DALK) have to be used. Due to the origin of the disease in the epithelial stem cells at the limbus, the replacement of these cells can also be discussed.

Visualization of corneal vascularization in peripheral hypertrophic subepithelial corneal opacification with OCT angiography

PURPOSE

The major goal of this study was to test the hypothesis that in patients with peripheral hypertrophic subepithelial corneal opacification (PHSCO), visualization of corneal vessels is better with optical coherence tomography angiography (OCTA) than with conventional slit lamp microphotography.

METHODS

Patients with PHSCO were included in this prospective study. The corneal findings were photographed using a slit lamp camera (Haag Streit BM 900^® ) and visualized with anterior-segment OCT (Optovue XR Avanti, Fremont, California, USA). Additionally, OCTA with the Angiovue Imaging™ System was performed in the area of PHSCO.

RESULTS

Thirty-four eyes of 19 patients (26% male and 74% female) with PHSCO were included in this study. In 21 eyes, vascularization in the area of PHSCO was visualized with the Angiovue-OCT, whereas only 10 eyes presented vessels in slit lamp photographs.

CONCLUSION

Optical coherence tomography angiography allows better visualization of corneal neovascularization than slit lamp photography in patients with PHSCO. Corneal opacifications were found predominantly nasally, which was reflected by a local enlargement of corneal thickness.

Recurrence of paraproteinemic keratopathy after penetrating keratoplasty and its assessment with confocal microscopy

Purpose

To report on a case of recurrence of paraproteinemic keratopathy (PPK) associated with monoclonal gammopathy after bilateral penetrating keratoplasty.

Observations

Penetrating keratoplasty was performed on both eyes of a 45-year-old man due to bilateral progressive corneal stromal clouding. Recurrence of the corneal stromal opacities accompanied by a decrease in visual acuity was observed on slit-lamp examination already two years after penetrating keratoplasty. Confocal laser scanning microscopy (CLSM) of the corneal grafts performed three years after penetrating keratoplasty showed bilateral morphological changes identical to that found in the patient's corneas prior to penetrating keratoplasty. A hematological work-up revealed monoclonal gammopathy of type IgG kappa. The histochemical examination of the explanted corneas confirmed the diagnosis of PPK.

Conclusions and importance

Paraproteinemic keratopathy is an underdiagnosed ophthalmological condition, which may be associated with potentially life-threatening hematologic disorders. A hematological workup should be performed in patients with corneal opacities of uncertain etiology. Penetrating keratoplasty should be performed with caution in patients with monoclonal gammopathy due to the possibility of a very fast recurrence of PPK in the corneal graft. This is the first presentation of the recurrence of flake-like PPK after penetrating keratoplasty assessed with CLSM.

[Recurrent Corneal Erosions in Epithelial Corneal Dystrophies]

The corneal epithelium is the most important structure of the ocular optical system. Recurrent corneal erosions can result from inflammation, trauma, degeneration and dystrophies. Epithelial basement membrane dystrophy (EBMD), epithelial recurrent erosion dystrophy (ERED) and Francheschetti and Meesmann's epithelial corneal dystrophy (MECD) can all - besides other signs and symptoms - result in more or less frequent corneal erosions. The pathomechanisms involved however are different. In EBMD, corneal erosions are facultative and clinical signs are often subtle. Aberrant basement membrane structures are associated with thinning of the epithelium and can be clinically identified as maps or fingerprints. In ERED, recurrent corneal erosions are - predominantly in the first decades of life - always present. A defect in the COL17A1 gene results in a dysfunctional hemidesmosome. In MECD, punctate corneal erosions are less frequent and result from intraepithelial microcysts which open spontaneously onto the ocular surface. Usually lubricants, therapeutic contact lenses and sometimes epithelial debridement and phototherapeutic keratectomy are the mainstay for treating corneal erosions in these three dystrophies.

[Paraproteinemic Keratopathy as a Clinical Sign of Monoclonal Gammopathy]

Patients with monoclonal gammopathy can show paraproteinemic keratopathy (PPK) with an indication to treatment. PPK has to be differentiated from corneal dystrophies, systemic metabolic disorders with corneal involvement, as well as from immunologic and inflammatory corneal diseases.

The Hematologic Definition of Monoclonal Gammopathy of Undetermined Significance in Relation to Paraproteinemic Keratopathy (An American Ophthalmological Society Thesis)

PURPOSE

To determine if paraproteinemic keratopathy (PPK) in the setting of monoclonal gammopathy of undetermined significance (MGUS) causes distinct patterns of corneal opacification that can be distinguished from hereditary, immunologic, or inflammatory causes.

METHODS

A retrospective, interventional study of patients showed distinct bilateral opacity patterns of the cornea at the eye clinics of Hanau, Mainz, Helsinki, Marburg, and Berlin between 1993 and 2015. Data on patient characteristics and clinical features on ophthalmic examination were collected, and serum protein profiles were evaluated. A literature review and analysis of all published studies of MGUS with PPK is also presented.

RESULTS

The largest group of patients diagnosed with MGUS-induced PPK is analyzed in this study. We studied 22 eyes of 11 patients (6 male, aged 43 to 65, mean age 54; 5 female, aged 49 to 76, mean age 61) with distinct corneal opacities and visual impairment who were first suspected of having hereditary, inflammatory, or immunologic corneal entities. Subsequently, serum protein electrophoresis revealed MGUS to be the cause of the PPK. Literature review revealed 72 patients with bilateral PPK (34 male, mean age 57; 38 female, mean age 58) in 51 studies of MGUS published from 1934 to 2015 and disclosed six additional corneal opacity patterns.

CONCLUSIONS

This thesis shows that MGUS is not always an asymptomatic disorder, in contrast to the hematologic definition, which has no hint of PPK. The MGUS-induced PPK can mimic many other diseases of the anterior layer of the eye. A new clinical classification for PPK in MGUS is proposed.

Erratum: The Hematologic Definition of Monoclonal Gammopathy of Undetermined Significance in Relation to Paraproteinemic Keratopathy (An American Ophthalmological Society Thesis)

[This corrects the article on p. T7 in vol. 114, PMID: 28050052.].

Professor Dr Med Oskar Fehr: the fate of an outstanding German-Jewish ophthalmologist: an early contributor to cornea and external disease

PURPOSE

The aim of this study was to recount the immense and abrupt change in the private and professional life of a prominent German-Jewish ophthalmologist in the transition from democracy to dictatorship in Germany during the first half of the 20th century.

METHODS

This involves a Retrospective analysis of Fehr's clinical and scientific work as the first assistant of Julius Hirschberg's world-famous eye clinic in Berlin; evaluation of Fehr's successful tenure as a chair of Virchow's Eye Hospital; the catastrophic influence of Hitler's seizure of power on the private and professional lives of German-Jewish physicians; and an analysis of Fehr's personal and professional will to continue the practice of medicine in England.

RESULTS

Oskar Fehr published >50 articles and was the first to describe the endemic swimming pool conjunctivitis. He was the first to specifically distinguish granular, lattice, and macular corneal dystrophies. Professor Oskar Fehr was the chair of one of the most important eye clinics in Germany for nearly 30 years. The "Anti-Jewish Medical Laws" with their terrible consequences on private and professional lives led to Fehr's emigration from his homeland to England in 1939. He obtained a British medical doctor degree after 4 years of study, and at an advanced age, he demonstrated his determination to practice ophthalmology successfully in London. Oskar Fehr died in London on August 1, 1959.

[Corneal dystrophy (CD)-induced pain and visual impairment in childhood]

Many forms of the 25 corneal dystrophies (CD) manifest already in childhood with bilateral corneal opacities without any visual impairment in most cases. Pain attacks due to recurrent erosion with red eye and epiphora can occur in combination with the first dystrophy-specific corneal opacities, e.g., nest-like lattice lines + corneal erosion in lattice CD. Often we can observe a joint occurrence. The parents accompany their child to consult the ophthalmologist concerning the recurrent and joint pain attacks. The ophthalmologist can also diagnose in such a situation subtle corneal opacities on the painless, contralateral eye, e.g., those of lattice, granular, macular or Reis-Bücklers CD. The correct interpretation of this combination does not lead the ophthalmologist to an inflammatory-, but to a dystrophy-induced interpretation of this entity. In a further group of CD, e.g., in Franceschetti CD, the typical history of this entity is a dominant disorder with recurrent epithelial erosions starting in the first decade, declining in frequency and severity at a later age, and associated with a central, disk-like haze of the subepithelial cornea from middle age. The recurrent erosions in childhood lasted 3-5 days and were followed by complete recovery. Congenital corneal clouding in the form of a milky ground-glass appearance can be observed in the rare endothelial CD, such as in congenital hereditary endothelial dystrophy 1 and 2 (CHED 1 and 2), X-linked endothelial CD (XECD), and in posterior polymorphous CD (PPCD). The differential diagnosis for congenital glaucoma is of essential importance. The parents of babies with congenital corneal opacification should be examined at the slit-lamp to in- or exclude the appearance of mooncrater-like endothelial changes.

[Therapy for systemic metabolic disorders based on the detection of basic corneal landmarks in childhood]

Many systemic lysosomal storage disorders show basic corneal opacities already in childhood. The lysosome is a cell organelle, produced by Golgi's apparatus, that is surrounded by a membrane and contains hydrolytic enzymes that break down food molecules, especially proteins and other complex molecules. The ophthalmologist's precise diagnosis of corneal clouding at the slit-lamp may reveal the correct interpretation of the specific lysosomal storage disorder. It is very important to diagnose such diseases as soon as possible because today the development of systemic enzymatic therapies has broadened the therapeutic armamentarium for the current standard of care. The following corneal landmarks of systemic storage diseases and of the modern systemic therapy are presented: cornea verticillata in Fabry's disease, periodic infusion of alpha-galactosidase a; Kayser-Fleischer's ring in Wilson's disease, zinc, trienetin, low copper diet; multiple, punctiform crystals in cystinosis, cysteamine, Raptor RP 103(DR cysteamine) that reduces the cytotoxity in form of continous dissolving of cystine from lysosome, renal transplantation, haematopoietic stem cell transplantation; peripheral ring, but not true lipid arc, and moderate stromal haze in LCAT-deficiency, injection of recombinant enzyme or of encapsulated LCAT-secreting cells; diffuse stromal haze in mucopolysaccharidoses (MPS). Enzyme replacement therapy is currently indicated for MPS I, MPS II, and MPS VI, haematopoietic stem cell transplantation; painful, bilateral pseudo-dendritic opacities in tyrosinemia type II (eponym: Richner-Hanhart syndrome), low phenylalanine and tyrosine diet result in complete disappearance of corneal alterations with a consecutive painfree period. Strict diet during the whole life is necessary to prevent corneal recurrences and the occurrence of palmo-plantar keratoses. Such therapies can enable the patient to lead an otherwise normal life for decades.

[Discrete bilateral corneal deposits in a young woman]

A 17-year-old asymptomatic girl presented with discrete bilateral deposits in the superficial corneal stroma. The diagnosis of very early and in this form as yet undescribed manifestation of Schnyder's corneal dystrophy, was only possible based on the family history.

Franceschetti hereditary recurrent corneal erosion

PURPOSE

To describe new affected individuals of Franceschetti's original pedigree of hereditary recurrent erosion and to classify a unique entity called Franceschetti corneal dystrophy.

DESIGN

Observational case series.

METHODS

Slit-lamp examination of 10 affected individuals was conducted. Biomicroscopic examinations were supplemented by peripheral corneal biopsy in 1 affected patient with corneal haze. Tissue was processed for light and electron microscopy and immunohistochemistry was performed. DNA analysis was carried out in 12 affected and 3 nonaffected family members.

RESULTS

All affected individuals suffered from severe ocular pain in the first decade of life, attributable to recurrent corneal erosions. Six adult patients developed bilateral diffuse subepithelial opacifications in the central and paracentral cornea. The remaining 4 affected individuals had clear corneas in the pain-free stage of the disorder. Histologic and immunohistochemical examination of the peripheral cornea in a single patient showed a subepithelial, avascular pannus. There was negative staining with Congo red. DNA analysis excluded mutations in the transforming growth factor beta-induced (TGFBI) gene and in the tumor-associated calcium signal transducer 2 (TACSTD2) gene.

CONCLUSION

We have extended the pedigree of Franceschetti corneal dystrophy and elaborated its natural history on the basis of clinical examinations. A distinctive feature is the appearance of subepithelial opacities in adult life, accompanied by a decreased frequency of recurrent erosion attacks. Its clinical features appear to distinguish it from most other forms of dominantly inherited recurrent corneal erosion reported in the literature.

[New international classification of corneal dystrophies (CD)]

The Cornea Society founded an international committee of 17 corneal experts from the USA, Asia and Europe in 2005. The goal of this group was to develop a new international classification of corneal dystrophies (CD) based on modern clinical, histological and genetic knowledge. Both authors are members of this committee. The elaboration of the classification included the correction of many misinterpretations with regard to the different forms of CD which were published in the past literature. In spite of important results concerning the genetic locus and identification of genes and mutations, corneal dystrophies are typically classified with respect to the level of the cornea that is involved. An accurate and up-to-date template for each form of the 25 CDs was created that included the current clinical, histological and genetic information. To indicate the level of evidence supporting the existence of a given dystrophy, the CDs are divided into four different categories. The new international classification of CDs was published in English, Spanish and German as a 40 page supplement with 64 figures, mostly in color. A more detailed description of genetic mutations is included in the appendix.

[Masquerade keratitis due to hereditary corneal disorders]

Hereditary corneal disorders can show a unilateral corneal erosion for several days due to different morphological etiologies which may result in the misdiagnosis of bacterial or viral keratitis. In such a situation it is very important to examine the contralateral eye with regard to a possible corneal opacity. The slit lamp examination has to be performed with dilated pupil in direct and indirect illumination. Patient history including familial ocular problems and recurrent alternating ocular pain can be a hint for the correct diagnosis. Masquerade keratitis of hereditary corneal disorders can be distinguished in 3 main groups: (i) recurrent corneal erosion due to systemic hereditary disorders with corneal involvement; (ii) recurrent corneal erosion due to corneal dystrophies with dystrophy-specific corneal opacities; (iii) recurrent corneal erosion in childhood without dystrophy-specific corneal opacities (occurrence of dystrophy-specific corneal opacities in adults). The ocular pain which may last several days with third group of patients often occurs in the second half of night. The children's suffering is enormous and has a negative impact on the whole family. The wearing of therapeutic contact lenses during the night may considerably reduce the ocular pain.

[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 .

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.

Genetic analysis of 14 families with Schnyder crystalline corneal dystrophy reveals clues to UBIAD1 protein function

Schnyder crystalline corneal dystrophy (SCCD) is a rare autosomal dominant disease characterized by progressive corneal opacification resulting from abnormal deposition of cholesterol and phospholipids. Recently, six different mutations on the UBIAD1 gene on chromosome 1p36 were found to result in SCCD. The purpose of this article is to further characterize the mutation spectrum of SCCD and identify structural and functional consequences for UBIAD1 protein activity. DNA sequencing was performed on samples from 36 individuals from 14 SCCD families. One affected individual was African American and SCCD has not been previously reported in this ethnic group. We identified UBIAD1 mutations in all 14 families which had 30 affected and 6 unaffected individuals. Eight different UBIAD1 mutations, 5 novel (L121F, D118G, and S171P in exon 1, G186R and D236E in exon 2) were identified. In four families with DNA samples from both affected and unaffected individuals, the D118G, G186R, T175I, and G177R mutations cosegregated with SCCD. In combination with our previous report, we have identified the genetic mutation in UBIAD1 in 20 unrelated families with 10 (including 5 reported here), having the N102S mutation. The results suggest that N102S may be a mutation hot spot because the affected families were unrelated including Caucasian and Asian individuals. There was no genotype phenotype correlation except for the T175I mutation which demonstrated prominent diffuse corneal haze, typically without corneal crystals. Protein analysis revealed structural and functional implications of SCCD mutations which may affect UBIAD1 function, ligand binding and interaction with binding partners, like apo E.

Mutations in the UBIAD1 gene on chromosome short arm 1, region 36, cause Schnyder crystalline corneal dystrophy

PURPOSE

Schnyder crystalline corneal dystrophy (SCCD; MIM 121800) is a rare autosomal dominant disease characterized by an abnormal increase in cholesterol and phospholipid deposition in the cornea, leading to progressive corneal opacification. Although SCCD has been mapped to a genetic interval between markers D1S1160 and D1S1635, reclassification of a previously unaffected individual expanded the interval to D1S2667 and included nine additional genes. Three candidate genes that may be involved in lipid metabolism and/or are expressed in the cornea were analyzed.

METHODS

DNA samples were obtained from six families with clinically confirmed SCCD. Analysis of FRAP1, ANGPTL7, and UBIAD1 was performed by PCR-based DNA sequencing, to examine protein-coding regions, RNA splice junctions, and 5' untranslated region (UTR) exons.

RESULTS

No disease-causing mutations were found in the FRAP1 or ANGPTL7 gene. A mutation in UBIAD1 was identified in all six families: Five families had the same N102S mutation, and one family had a G177R mutation. Predictions of the protein structure indicated that a prenyl-transferase domain and several transmembrane helices are affected by these mutations. Each mutation cosegregated with the disease in four families with DNA samples from both affected and unaffected individuals. Mutations were not observed in 100 control DNA samples (200 chromosomes).

CONCLUSIONS

Nonsynonymous mutations in the UBIAD1 gene were detected in six SCCD families, and a potential mutation hot spot was observed at amino acid N102. The mutations are expected to interfere with the function of the UBIAD1 protein, since they are located in highly conserved and structurally important domains.

[The different opacity patterns of Lisch corneal dystrophy]

BACKGROUND

Lisch corneal dystrophy is an epithelial corneal dystrophy where diffuse gray corneal opacifications are seen in direct illumination that appear in different patterns. Examination in retroillumination shows that these gray changes do consist of multiple densely crowded clear microcysts according to the opacity units. We wanted to investigate if one single case of Lisch corneal dystrophy can be differentiated easily from the other epithelial corneal dystrophies by exact analysis of the opacity units.

PATIENTS AND METHODS

We examined three non-related patients with Lisch corneal dystrophy at the slit-lamp. The epithelial corneal opacities were documented photographically with direct slit-lamp illumination and retroillumination.

RESULTS

All three patients showed the characteristic intraepithelial densely crowded clear microcysts in retroillumination. Diffuse gray radial opacities were noted in both corneas of a 15-year-old female patient. A club-shaped opacity was noted in one cornea of a 35-year-old female patient and a feathery gray opacity pattern was found in one cornea of a 49-year-old male patient. All three patients showed the characteristic densely crowded clear microcysts of Lisch corneal dystrophy in retroillumination.

CONCLUSION

Taking the previous literature into account, five different opacity patterns can be summarised: radial, band, flame/feathery, whorled and club-shaped gray epithelial corneal opacities. A single case of Lisch corneal dystrophy can be differentiated from other epithelial corneal dystrophies by means of an exact analysis of the opacity pattern and units by slit-lamp examination.

A new, X-linked endothelial corneal dystrophy

PURPOSE

To describe the clinical spectrum, the histopathologic findings obtained from one corneal button, and the genetic mapping of an X-linked endothelial corneal dystrophy (XECD).

DESIGN

Observational case series and experimental study.

METHODS

We examined a total of 60 members of a family with this dystrophy at the slit-lamp. Light and electron microscopic findings of the corneal button were recorded following one male patient's penetrating keratoplasty. A panel of 25 microsatellite markers covering the X chromosome was typed in genomic DNA from 50 family members. The data were analyzed using the ALLEGRO program to obtain two-point and multipoint likelihood of the odds (LOD) scores and to generate haplotypes.

RESULTS

A total of 35 trait carriers were identified in four generations of the family. Nine male patients demonstrated severe corneal opacifications: two congenital corneal cloudings in form of ground glass, milky appearance and seven subepithelial band keratopathies combined with endothelial changes resembling moon craters. Twenty-two female and four male patients disclosed only endothelial alterations resembling moon craters. No instance of male-to-male transmission of the disease was encountered in the family. Light and electron microscopy disclosed focal discontinuities and degeneration of the endothelial cell layer and marked thickening of Descemet's membrane. Multipoint analysis showed linkage with a maximum LOD score of 10.90 between markers DXS8057 and DXS1047.

CONCLUSIONS

To the best of our knowledge, this represents the first fully documented report of X-linked inheritance of an endothelial corneal dystrophy. Late subepithelial band keratopathy is a landmark of XECD. A locus for this corneal dystrophy maps to Xq25.