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

IntroductionAs 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.MethodComputer video-keratoscopy (CVK) was undertaken was on this family to clarify this apparent discordance.ResultsCVK demonstrated the variable expression of the keratoconic phenotype, by identifying evidence of subclinical keratoconus in the ‘unaffected’ twin.ConclusionSo 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.