The variable expression of keratoconus within monozygotic twins: Dundee University Scottish Keratoconus Study (DUSKS)

Abstract 

Introduction

As part of a longitudinal observational prospective study (Dundee University Scottish Keratoconus Study, DUSKS) a caucasian female subject was identified with keratoconus affecting both corneas. Of interest was that the subject's mother was a monozygotic twin, however, the mother was reportedly unaffected by keratoconus, although her sister (the subject's aunt) had been diagnosed with keratoconus.

Method

Computer video-keratoscopy (CVK) was undertaken was on this family to clarify this apparent discordance.

Results

CVK demonstrated the variable expression of the keratoconic phenotype, by identifying evidence of subclinical keratoconus in the ‘unaffected’ twin.

Conclusion

So far only one set of monozygotic twins with keratoconus have been reported within the UK, this paper reports a second. Since CVK has been available the majority agree on concordance of keratoconus expression but not all, including this study. If monozygotic twin studies demonstrate heterogeneity of keratoconus this may at least explain the contradictory data that exists within the literature and why the inheritance pattern of keratoconus is still unclear in 2005.

Keywords: Keratoconus, Monozygotic twins, Corneal topography