Abstract
Purpose: :
Corneal dystrophies of Bowman’s layer (CDB), also known as Reis-Bucklers corneal dystrophy (RBCD or CDBI) and Thiel-Behnke corneal dystrophy (TBCD or CDBII), are associated with conserved mutations in the transforming growth factor beta-induced (TGFBI) gene. As RBCD and TBCD can be difficult to distinguish based on clinical features alone, we screened TGFBI in an Argentinean family with a classic CDB phenotype.
Methods: :
Slit-lamp examination was performed on affected members of a large pedigree with 9 affected individuals in 3 consecutive generations. Genomic DNA was isolated from saliva and used for automated screening of the complete coding sequence of TGFBI (17 exons and intron-exon boundaries).
Results: :
Affected individuals demonstrated confluent gray-white opacities at the level of Bowman’s layer that appeared in a reticular pattern in several patients, consistent with RBCD and TBCD. Sequencing of TGFBI exons 4 and 12 failed to reveal the conserved mutations associated with RBCD and TBCD, but did identify a non-pathogenic synonymous substitution (p.Leu472Leu). Screening of the remaining 15 exons revealed two other non-pathogenic synonymous substitutions (p. Phe540Phe and p.Val327Val), but failed to indentify a presumed pathogenic sequence variant.
Conclusions: :
The exclusion of a TGFBI coding region mutation in the dominantly inherited Bowman’s layer dystrophy that we report raises the possibility of a novel corneal dystrophy. As linkage to chromosome 10q23-q24 has been demonstrated in another family in which linkage to the TGFBI locus was excluded, we plan to perform a genome-wide association study to identify linkage to chromosome 10q or another locus.
Keywords: degenerations/dystrophies • genetics • gene screening