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Macular corneal dystrophy in Iceland. A clinical, genealogic, and immunohistochemical study of 28 patients
F Jonasson1, E Oshima, E J Thonar
1University Department of Ophthalmology, Landakot Hospital, Reykjavik, Iceland.
Background:
The frequency of different types of macular corneal dystrophy (MCD) was determined in Iceland where MCD accounts for one third of every penetrating keratoplasty.
Methods:
The authors determined the serum levels of antigenic keratan sulfate (aKS) in 27 patients with MCD and 53 unaffected family members by an enzyme-linked immunosorbent assay that uses an anti-KS monoclonal antibody (5-D-4). The authors also stained sections from 37 corneal buttons (including 2 regrafts) from 23 patients with MCD by the avidin-biotin complex method using the same anti-KS monoclonal antibody.
Results:
Based on the serum analyses, 22 patients had MCD type I and 5 had MCD type II. The corneas from patients without detectable KS in the serum lacked immunohistochemical reactivity to the anti-KS antibody. Every MCD cornea examined from individuals with normal serum KS levels showed KS reactivity. All 53 unaffected siblings and parents carrying the recessive gene had normal serum KS levels.
Conclusions:
Macular corneal dystrophy types I (78.6%) and II (21.4%) both occur in Iceland. Members of affected sibships had only one of these types, not both. Nine patients with MCD type I and four persons with MCD type II belonged to a large pedigree in which individuals have been traced as far back as the beginning of the 16th century. The linking of patients with MCD types I and II in an inbred pedigree suggests that both types may be manifestations of the same abnormal gene rather than independent entities. The serum KS levels were not helpful in detecting heterozygous MCD carriers.
Insights
Macular corneal dystrophy (MCD) types I and II occur in Iceland, with both potentially stemming from the same gene. Serum keratan sulfate levels did not help identify carriers of this rare eye condition.
Area of Science:
- Ophthalmology
- Genetics
- Biochemistry
Background:
- Macular corneal dystrophy (MCD) is a significant cause of corneal transplantation in Iceland, accounting for one-third of all cases.
- This study investigates the prevalence and genetic basis of different MCD types within the Icelandic population.
Purpose of the Study:
- To determine the frequency of Macular Corneal Dystrophy (MCD) types I and II in Iceland.
- To investigate the genetic linkage between MCD types I and II within a large Icelandic pedigree.
- To evaluate the utility of serum antigenic keratan sulfate (aKS) levels in diagnosing MCD and identifying carriers.
Main Methods:
- Serum antigenic keratan sulfate (aKS) levels were measured using ELISA in 27 MCD patients and 53 family members.
- Corneal tissue sections from 23 MCD patients were analyzed for KS presence using immunohistochemistry (avidin-biotin complex method).
Main Results:
- Serum analysis identified 22 patients with MCD type I and 5 with MCD type II.
- Corneal staining confirmed KS presence in MCD corneas from individuals with normal serum KS levels.
- All unaffected family members carrying the recessive gene had normal serum KS levels, indicating serum KS is not a reliable carrier detection method.
Conclusions:
- Macular corneal dystrophy types I (78.6%) and II (21.4%) are present in Iceland.
- The occurrence of both MCD types within a single, inbred pedigree suggests they may be allelic forms of the same gene.
- Serum KS levels are not effective for detecting heterozygous carriers of macular corneal dystrophy.
