Abstract
Purpose: :
Strabismus is a common eye disorder with a prevalence of 1-4%. Comitant strabismus accounts for approximately 75% of all strabismus, yet more is known about the less common, incomitant disorders. For comitant strabismus, only one susceptibility locus [STBMS1] has been identified to date, in one family, on chromosome 7p. To determine the frequency of STBMS1 as a cause of primary nonsyndromic comitant esotropia [PNCE], we have ascertained, sampled and genotyped twelve families with PNCE.
Methods: :
Families were recruited within the UK Hospital Eye Service, whereby a child was attending for treatment of PNCE. All consenting members of a family were clinically assessed and DNA was sampled. Chromosome 7 markers were genotyped in all twelve families then further markers were tested at STBMS1 in one linked family. LOD scores were calculated under recessive and dominant models with the programs GENEHUNTER and LINKMAP.
Results: :
One family [CA/CL] was linked to STBMS1, three significantly excluded linkage and the remainder were uninformative. Twenty-six members from three generations of the CA/CL pedigree were analysed further, five of which were defined as affected. Two individuals had esotropia with an accommodative element; three had strabismus surgery and appear to have had an ‘infantile-type’ of esotropia. A maximum LOD score of 3.21 was obtained under a dominant mode of inheritance; a recessive model gave a LOD score of 1.2.
Conclusions: :
This study confirms that PNCE can result from sequence variants at the STBMS1 locus. However, this locus accounts for only a proportion of cases and other genetic loci remain to be identified. In contrast with the previous reported family, this study suggests dominant rather than recessive inheritance at the STBMS1 locus.
Keywords: genetics • strabismus • linkage analysis