TGFBI gene mutations in corneal dystrophies.

The lattice corneal dystrophies (LCD) and granular corneal dystrophies (GCD) are autosomal dominant disorders of the corneal stroma. They are bilateral, progressive conditions characterized by the formation of opacities arising due to the deposition of insoluble material in the corneal stroma leading to visual impairment. The LCDs and GCDs are distinguished from each other and are divided into subtypes on the basis of the clinical appearance of the opacities, clinical features of the disease, and on histopathological staining properties of the deposits. The GCDs and most types of LCD arise from mutations in the transforming growth factor beta-induced (TGFBI) gene on chromosome 5q31. Over 30 mutations causing LCD and GCD have been identified so far in the TGFBI. There are two mutation hotspots corresponding to arginine residues at positions 124 and 555 of the transforming growth factor beta induced protein (TGFBIp) and they are the most frequent sites of mutation in various populations. Mutations at either of these two hotspots result in specific types of LCD or GCD. The majority of identified mutations involve residues in the fourth fasciclin-like domain of TGFBIp.