| Macular corneal dystrophy | |
|---|---|
 | |
| Colloidal iron staining shows deposition of glycosaminoglycans in the cornea |
Macular Corneal Dystrophy (MCD), also known as Fehr Corneal Dystrophy, is a rare pathological condition affecting the corneal stroma first described by Arthur Groenouw in 1890.[1] Signs are usually noticed in the first decade of life and progress afterwards, with opacities developing in the cornea and attacks of pain. This gradual opacification leads to visual impairment often requiring keratoplasty in the later decades of life.[2]
Epidemiology
editWhile Macular Corneal Dystrophy is found throughout the world, countries with the highest prevalence include Iceland, Saudi Arabia, India, and the United States.[3][4][5] In Iceland, MCD accounts for almost one-third of all corneal grafts performed.[4] Estimates from Claims Data in the United States place the prevalence of MCD at 9.7 per million, which represents less than 1% of corneal dystrophies.[6]
Pathophysiology
editMacular Corneal Dystrophy is an autosomal recessive genetic disorder caused by mutations in the carbohydrate sulfotransferase gene (CHST6), resulting in abnormal proteoglycan synthesis. The accumulation of abnormal glycosaminogycans in the corneal epithelium and stroma leads to progressive opacification of the cornea and subsequent loss of visual acuity.[7][8] There are three variants of MCD characterized by immunophenotype:
| Variant | Keratan Sulfate in Serum | Keratan Sulfate in Cornea |
|---|---|---|
| Type 1 | Absent | Absent |
| Type 1A | Absent | Antibodies present |
| Type 2 | Present | Present |
- Type 1: no detectable keratan sulfate in either the serum or cornea
- Type 1A: keratan sulfate is absent in the serum but stroma shows immunoreactivity to keratan sulfate antibodies
- Type 2: normal amounts of keratan sulfate in the serum and stroma
These three variants are clinically and histopathologically indistinguishable.[9]
Signs & Symptoms
edit
The first signs of MCD are cloudy regions that appear on the cornea during adolescence, although opacification may be noticed as early as the first decade.[2] These minute, gray, punctate opacities will overtime merge into larger areas, causing the entire corneal stroma to become opaque. Ultimately this results in severe visual impairment, generally before the 5th decade of life.[2]
While some individuals remain asymptomatic, initial symptoms typically consist of painful attacks with photophobia, foreign body sensations, and recurrent erosions.[7] Corneal sensitivity is also reduced.[2]
Diagnosis
editHistopathological staining shows characteristic alcian blue-positive deposits.[7] Various imaging modalities, including confocal microscopy and ocular coherence tomography, can provide information about the changes within the cornea and may be suitable replacements for tissue biopsy and excision.[8]
Treatment & Prognosis
editWhen visual acuity is impacted, various forms of keratoplasty are often indicated. While corneal transplant has traditionally been the standard treatment, less-invasive surgical techniques such as deep anterior lamellar keratoplasty and photo-therapeutic keratectomy are increasingly playing a role in management of MCD.[8] While post-operative prognosis is favorable, reoccurrences may occur.[7]
Various gene therapies, including enzyme replacement therapy and gene-targeting therapy, remain a potential future treatment modality for MCD.[8]
See also
editReferences
edit- ^ Groenouw A. Knötchenförmige Hornhauttrübungen (noduli corneae). Arch Augenheilkunde. 1890;21:281–289.
- ^ a b c d Klintworth, Gordon K. (2009-02-23). "Corneal dystrophies". Orphanet Journal of Rare Diseases. 4: 7. doi:10.1186/1750-1172-4-7. ISSN 1750-1172. PMC 2695576. PMID 19236704.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ al Faran, M. F.; Tabbara, K. F. (1991-01). "Corneal dystrophies among patients undergoing keratoplasty in Saudi Arabia". Cornea. 10 (1): 13–16. ISSN 0277-3740. PMID 2019101.
{{cite journal}}: Check date values in:|date=(help) - ^ a b Jonasson, F.; Johannsson, J. H.; Garner, A.; Rice, N. S. (1989). "Macular corneal dystrophy in Iceland". Eye (London, England). 3 ( Pt 4): 446–454. doi:10.1038/eye.1989.66. ISSN 0950-222X. PMID 2606219.
- ^ Pandrowala, Hijab; Bansal, Aashish; Vemuganti, Geeta K.; Rao, Gullapalli N. (2004-08). "Frequency, distribution, and outcome of keratoplasty for corneal dystrophies at a tertiary eye care center in South India". Cornea. 23 (6): 541–546. doi:10.1097/01.ico.0000126324.58884.b9. ISSN 0277-3740. PMID 15256989.
{{cite journal}}: Check date values in:|date=(help) - ^ Musch, David C.; Niziol, Leslie M.; Stein, Joshua D.; Kamyar, Roheena M.; Sugar, Alan (2011-09-01). "Prevalence of corneal dystrophies in the United States: estimates from claims data". Investigative Ophthalmology & Visual Science. 52 (9): 6959–6963. doi:10.1167/iovs.11-7771. ISSN 1552-5783. PMC 3175990. PMID 21791583.
- ^ a b c d Singh, Shalini; Das, Sujata; Kannabiran, Chitra; Jakati, Saumya; Chaurasia, Sunita (2021-06). "Macular Corneal Dystrophy: An Updated Review". Current Eye Research. 46 (6): 765–770. doi:10.1080/02713683.2020.1849727. ISSN 1460-2202. PMID 33171054.
{{cite journal}}: Check date values in:|date=(help) - ^ a b c d Aggarwal, Shruti; Peck, Travis; Golen, Jeffrey; Karcioglu, Zeynel A. (2018). "Macular corneal dystrophy: A review". Survey of Ophthalmology. 63 (5): 609–617. doi:10.1016/j.survophthal.2018.03.004. ISSN 1879-3304. PMID 29604391.
- ^ Klintworth, G. K.; Smith, C. F. (1977-10). "Macular corneal dystrophy. Studies of sulfated glycosaminoglycans in corneal explant and confluent stromal cell cultures". The American Journal of Pathology. 89 (1): 167–182. ISSN 0002-9440. PMC 2032199. PMID 143892.
{{cite journal}}: Check date values in:|date=(help)