Extremely varied phenotypes in granular corneal dystrophy type 2 heterozygotes

Area of Science:

• Ophthalmology
• Genetics
• Molecular Biology

Background:

• Granular corneal dystrophy type 2 (GCD2) is a genetic eye condition.
• It is caused by mutations in the transforming growth factor-beta-induced (TGFBI) gene.
• The R124H mutation is a common cause of GCD2.

Purpose of the Study:

• To investigate the phenotypic variability in patients with the heterozygous R124H mutation in the TGFBI gene.
• To understand the range of disease severity in GCD2 patients with this specific mutation.

Main Methods:

• Described the phenotypic range of GCD2 heterozygotes for the R124H mutation.
• Collected detailed slit-lamp photographs.
• Performed DNA analysis to confirm heterozygous GCD2.
• Compared TGFBIp expression in cultured corneal fibroblasts.

Main Results:

• Observed profound differences in phenotype severity among patients.
• Two mild phenotype patients were initially diagnosed as unaffected.
• Familial clustering of phenotypic variance was noted, with similar severity within families.
• TGFBIp expression levels varied among different donor-derived fibroblasts.

Conclusions:

• GCD2 heterozygotes exhibit extreme phenotypic variability.
• Phenotypes were broadly consistent within families, suggesting regulation by other genetic factors.
• Genetic analysis and meticulous clinical examination are crucial for diagnosis and management.