Macular Corneal Dystrophy in 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.