Abstract
Purpose: :
To describe the phenotype and hereditability of 16 sets of twins with keratoconus.
Methods: :
Twins and available first-degree relatives were examined as part of a study into familial keratoconus. Zygosity was established by genotyping of 16 forensic microsatellite markers in 14 twin sets. In one pair the other twin was unavailable and in one pair genotyping was not performed as the sex was opposite.
Results: :
In total, including the two pairs that were not genotyped, 5 pairs were dizygotic (DZ) and 11 monozygotic (MZ). All but one pair of DZ twins were concordant for keratoconus but two pairs exhibited major differences in age of onset, severity, and progression of the disease. All 11 MZ twins were concordant for keratoconus and 9 of these pairs had a similar age of onset and disease severity. In four of the families with DZ twins other relatives also had keratoconus, but only two families with MZ twins had another relative affected.
Conclusions: :
Greater phenotype concordance in MZ than DZ twins supports a major genetic contribution towards the pathogenesis of keratoconus.
Keywords: keratoconus • genetics • topography