title: The variable expression of keratoconus within monozygotic twins: dundee University Scottish Keratoconus Study (DUSKS).
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors: Ophthalmology Department, Ninewells Hospital and Medical School, Dundee, Scotland DD1 9SY, United Kingdom. k.h.weed@dundee.ac.uk
authors: K H
authors: KH
authors: Weed
authors: C J
authors: CJ
authors: MacEwen
authors: C N J
authors: CN
authors: McGhee