Lattice corneal dystrophy type 1: an epithelial or stromal entity?
To evaluate the question whether lattice corneal dystrophy type 1 (LCD1) is of epithelial or stromal origin.The landmark of advanced LCD1 shows central superficial haze and paracentral stromal lattice lines. In 16 eyes of 8 affected individuals of 2 families, a penetrating keratoplasty was performed. The follow-up was 8 to 16 years after penetrating keratoplasty. Slit-lamp documentation of the patients was evaluated in direct and indirect illumination with dilated pupil to assess the horizontal and vertical pattern of new deposits on the corneal graft. Three affected patients of 2 families are demonstrated in detail. A DNA analysis was performed.Gene identification revealed a transforming growth factor beta-induced (TGFBI) Leu509Pro mutation in the first family, and a TGFBI Arg124Cys mutation in the second family. The demonstrated 5 corneal grafts of the 3 LCD1-patients showed diffuse opacities of distinct severity, beginning 3 to 4 years postoperatively, that were often combined with corneal erosions and consecutive pain. In none of our patients, we were able to detect any signs of lattice formation in the form of gray lines that run obliquely from the surface to the midstroma in direct illumination. In retroillumination, no lattice opacity units in the form of translucent and refractile lines were visible on the graft.The TGFBI gene, that is responsible for LCD1, is expressed above all by the corneal epithelial cells but also by the keratocytes. We interpret the superficial diffuse LCD1 recurrences on the graft as the product of the epithelial cells, whereas the nonoccurrence of lattice lines as long as 18 years after keratoplasty, an indirect sign that the lattice lines are the product of the keratocytes. Thus, LCD1 seems to represent an epithelial-stromal entity, because both epithelial cells and keratocytes are involved.